Journal articles on the topic 'Volcanis islands'
To see the other types of publications on this topic, follow the link: Volcanis islands.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Volcanis islands.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Smellie, John L. "Chapter 3.2a Bransfield Strait and James Ross Island: volcanology." Geological Society, London, Memoirs 55, no. 1 (2021): 227–84. http://dx.doi.org/10.1144/m55-2018-58.
Abstract:
AbstractFollowing more than 25 years of exploration and research since the last regional appraisal, the number of known subaerially exposed volcanoes in the northern Antarctic Peninsula region has more than trebled, from less than 15 to more than 50, and that total must be increased at least three-fold if seamounts in Bransfield Strait are included. Several volcanoes remain unvisited and there are relatively few detailed studies. The region includes Deception Island, the most prolific active volcano in Antarctica, and Mount Haddington, the largest volcano in Antarctica. The tectonic environment of the volcanism is more variable than elsewhere in Antarctica. Most of the volcanism is related to subduction. It includes very young ensialic marginal basin volcanism (Bransfield Strait), back-arc alkaline volcanism (James Ross Island Volcanic Group) and slab-window-related volcanism (seamount offshore of Anvers Island), as well as volcanism of uncertain origin (Anvers and Brabant islands; small volcanic centres on Livingston and Greenwich islands). Only ‘normal’ arc volcanism is not clearly represented, possibly because active subduction virtually ceased atc.4 Ma. The eruptive environment for the volcanism varied between subglacial, marine and subaerial but a subglacial setting is prominent, particularly in the James Ross Island Volcanic Group.
2
McDOUGALL, IAN. "Age of volcanism and its migration in the Samoa Islands." Geological Magazine 147, no. 5 (February 10, 2010): 705–17. http://dx.doi.org/10.1017/s0016756810000038.
Abstract:
AbstractPotassium–argon (K–Ar) ages on whole rock samples have been measured on lavas from the subaerial Samoa Islands, which form a broadly linear volcanic chain that extends from the ESE to the WNW for about 360 km. The Manu'a Islands near the southeast limit of the chain exhibit youthful ages, with most <0.4 Ma, in keeping with the geological observations. Tutuila consists of several volcanoes, and previous work yielded a mean K–Ar age of 1.26 ± 0.15 Ma for the shield-building volcanism. Upolu, to the WNW of Tutuila, gives a mean age of 2.15 ± 0.35 Ma for the shield-building phase, represented by the Fagaloa Volcanics, with much of the island covered by significantly younger volcanic rocks. Savai'i, further to the WNW, is dominated by youthful volcanism, extending into historic times. In a restricted area, adjacent to the NE coast of Savai'i, previously thought to have volcanic rocks correlating with the Fagaloa Volcanics of Upolu, the ages are much younger than those on Upolu, lying between 0.32 and 0.42 Ma. Considering only the subaerial volcanism from Ta'u to Upolu, but also including Vailulu'u, the volcanism has migrated in a systematic ESE direction at 130 ± 8 mm a−1 over 300 km in the last 2.2 Ma. This rate is nearly twice that obtained from GPS measurements of Pacific Plate motion of 72 mm a−1 at N64°W in this area. However, if the much older age of shield-building volcanism from the submarine foundations of Savai'i is included, the regression yields a volcanic migration rate of 72 ± 14 mm a−1, in keeping with the measured GPS rate and consistent with a hotspot origin for the island chain. This suggests that the volcanic migration rates determined from the age of subaerial volcanism can be considerably overestimated, and this is now evident in other Pacific Ocean island chains. Clearly, the ages of the main shield-building volcanism from subaerial volcanism are minima, and if the older submarine lavas can be measured, these may yield a migration rate more in keeping with current plate motions.
3
Simurda, Christine, Lori A. Magruder, Jonathan Markel, James B. Garvin, and Daniel A. Slayback. "ICESat-2 Applications for Investigating Emerging Volcanoes." Geosciences 12, no. 1 (January 14, 2022): 40. http://dx.doi.org/10.3390/geosciences12010040.
Abstract:
Submarine volcanism in shallow waters (<100 m), particularly in remote settings, is difficult to monitor quantitatively and, in the rare formation of islands, it is challenging to understand the rapid-paced erosion. However, these newly erupted volcanic islands become observable to airborne and/or satellite remote sensing instruments. NASA’s ICESat-2 satellite laser altimeter, combined with visible imagery (optical and microwave), provide a novel method of evaluating the elevation characteristics of newly emerged volcanoes and their subaerial eruption products. Niijima Fukutoku-Okanoba (NFO) is a submarine volcano 1300 km south of Tokyo (Ogasawara Archipelago of Japan) that periodically breaches the ocean surface to create new islands that are subsequently eroded. The recent eruption in August 2021 is a rare opportunity to investigate this island evolution using high-resolution satellite datasets with geodetic-quality ICESat-2 altimetry. Lansdat-8 and Planet imagery provide a qualitative analysis of the exposed volcanic deposits, while ICESat-2 products provide elevation profiles necessary to quantify the physical surface structures. This investigation determines an innovative application for ICESat-2 data in evaluating newly emerged islands and how the combination of satellite remote sensing (visible and lidar) to investigate these short-lived volcanic features can improve our understanding of the volcanic island system in ways not previously possible.
4
Leat, Philip T., and Teal R. Riley. "Chapter 3.1a Antarctic Peninsula and South Shetland Islands: volcanology." Geological Society, London, Memoirs 55, no. 1 (2021): 185–212. http://dx.doi.org/10.1144/m55-2018-52.
Abstract:
AbstractThe voluminous continental margin volcanic arc of the Antarctic Peninsula is one of the major tectonic features of West Antarctica. It extends from the Trinity Peninsula and the South Shetland Islands in the north to Alexander Island and Palmer Land in the south, a distance ofc.1300 km, and was related to east-directed subduction beneath the continental margin. Thicknesses of exposed volcanic rocks are up toc.1.5 km, and the terrain is highly dissected by erosion and heavily glacierized. The arc was active from Late Jurassic or Early Cretaceous times until the Early Miocene, a period of climate cooling from subtropical to glacial. The migration of the volcanic axis was towards the trench over time along most of the length of the arc. Early volcanism was commonly submarine but most of the volcanism was subaerial. Basaltic–andesitic stratocones and large silicic composite volcanoes with calderas can be identified. Other rock associations include volcaniclastic fans, distal tuff accumulations, coastal wetlands and glacio-marine eruptions.Other groups of volcanic rocks of Jurassic age in Alexander Island comprise accreted oceanic basalts within an accretionary complex and volcanic rocks erupted within a rift basin along the continental margin that apparently predate subduction.
5
Griffiths, Chris J., and Richard D. J. Oglethorpe. "The stratigraphy and geochronology of Adelaide Island." Antarctic Science 10, no. 4 (December 1998): 462–75. http://dx.doi.org/10.1017/s095410209800056x.
Abstract:
The Mesozoic-Cenozoic volcanic arc of the Antarctic Peninsula is represented on Adelaide Island by a sedimentary and volcanic succession intruded by plutons. 40Ar-39 Ar step-heating age spectra have been obtained from volcanic rocks and hornblende separates from sedimentary clasts of plutonic origin. These spectra show evidence for some argon loss, but, in general, have plateau ages which are consistent with the mapped stratigraphy and with other geochronological controls, suggesting that they approximate to original ages. As a result the following events in the evolution of Adelaide Island can be recognized:1) mostly marine Mesozoic sedimentation, 2) Early Cretaceous (c. 141 Ma) plutonism (recorded in clasts from conglomerates), 3) Cretaceous volcanism, 4) Late Cretaceous (possibly Tertiary) sedimentation, 5) Early Tertiary volcanism, which was acidic in eastern outcrops and intermediate elsewhere, and 6) Eocene intermediate volcanism and deposition of arc-derived conglomerates. Volcanism was possibly coeval with known Palaeocene-Eocene plutonic activity on Adelaide Island (part of the Antarctic Peninsula Batholith) and with volcanism of similar age in northern Alexander Island and the South Shetland Islands. The volcanism on Adelaide Island and the South Shetland Islands, at least, was associated with a westward migration of the Antarctic Peninsula arc.
6
Geyer, A., D. Pedrazzi, J. Almendros, M. Berrocoso, J. López-Martínez, A. Maestro, E. Carmona, A. M. Álvarez-Valero, and A. de Gil. "Chapter 7.1 Deception Island." Geological Society, London, Memoirs 55, no. 1 (2021): 667–93. http://dx.doi.org/10.1144/m55-2018-56.
Abstract:
AbstractDeception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 15 explosive eruptive events registered over the past two centuries. Recent eruptions (1967, 1969 and 1970) and volcanic unrest episodes in 1992, 1999 and 2014–15 demonstrate that the occurrence of future volcanic activity is a valid and pressing concern for scientists, logistic personnel and tourists that are visiting or are working on or near the island. Over the last few decades, intense research activity has been carried out on Deception Island to decipher the origin and evolution of this very complex volcano. To that end, a solid integration of related scientific disciplines, such as tectonics, petrology, geochemistry, geophysics, geomorphology, remote sensing, glaciology, is required. A proper understanding of the island's evolution in the past, and its present state, is essential for improving the efficiency in interpreting monitoring data recorded during volcanic unrest periods and, hence, for future eruption forecasting. In this chapter, we briefly present Deception Island's most relevant tectonic, geomorphological, volcanological and magmatic features, as well as the results obtained from decades of monitoring the island's seismic activity and ground deformation.
7
Dimitrov, Dimitar, and Banush Banushev. "Geological-geomorphological characteristics and petrographical composition of the St. Anastasia Island." Acta Scientifica Naturalis 8, no. 1 (March 1, 2021): 118–25. http://dx.doi.org/10.2478/asn-2021-0010.
Abstract:
Abstract St. Anastasia Island is one of the symbols of the cultural and historical heritage of the Republic of Bulgaria. This raises the need for the study of risky oceanographic factors, climatic phenomena, risky geological processes as well as detailed petrographical characteristics of the Upper Cretaceous volcanic rocks forming the islands. The results of the petrographical study show that the island was built by Alkali feldspar trachytes. The volcanics from St. Anastasia Island shows a close petrochemical similarity to the volcanics from Alatepenski paleovolcano belonging to the “Peripheral Volcanic Centers” in the region.
8
Mutaqin, Bachtiar W., Muh Aris Marfai, Danang Sri Hadmoko, Franck Lavigne, Audrey Faral, Helvetia Wijayanti, and Widiyana Riasasi. "Geomorphology of the small island of Tidore and Hiri (North Maluku, Indonesia)." E3S Web of Conferences 325 (2021): 03012. http://dx.doi.org/10.1051/e3sconf/202132503012.
Abstract:
Tidore and Hiri Islands in North Maluku Province is the result of a complex tectonic setting. In contrast with Ternate Island and its well-known volcano, Gamalama volcano, there is still a lack of research about volcanic information or volcanic landform in Tidore and Hiri Islands. Even though the two islands also have volcanoes, i.e., Hiri and Tidore/Kiematubu volcano. This study aims to provide geomorphological information, especially in Tidore and Hiri Islands, since this information is hard to find whereas it is very important to disaster mitigation and landuse planning. We used remote sensing images, digital elevation models (DEM), and geological maps to classify geomorphological information of the small island of Tidore and Hiri in the North Maluku based on geomorphological aspects, i.e., morphology, morphogenesis, morpho-chronology, and morpho-arrangement. As a volcanic island, the slope in Tidore and Hiri Island is dominated by a slightly steep (8°-16°) and a steep slope (16°-35°), while the relief is dominated by hills and mountainous. Volcanic landforms on Tidore and Hiri Islands are characterized by relatively symmetrical cone-shaped volcanic cones, which are accumulations of falling pyroclastic material and lava ejected from magma vents. Volcanic islands include the case of Tidore and Hiri Island have radial centrifugal river flow patterns. The material on Tidore and Hiri Islands is dominated by Holocene volcanic rocks. In Tidore, there is alluvial material on the west and east coasts of the island. This study result also can be developed into more detailed geomorphological maps, or landscape evolution in a volcanic island, or spatial planning.
9
Patrick, Matthew R., and John L. Smellie. "Synthesis A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000–10." Antarctic Science 25, no. 4 (June 12, 2013): 475–500. http://dx.doi.org/10.1017/s0954102013000436.
Abstract:
AbstractOf the more than twenty historically active volcanoes in Antarctica and the sub-Antarctic region only two, to our knowledge, host any ground-based monitoring instruments. Moreover, because of their remoteness, most of the volcanoes are seldom visited, thus relegating the monitoring of volcanism in this region almost entirely to satellites. In this study, high temporal resolution satellite data from the Hawaii Institute of Geophysics and Planetology's MODVOLC system using MODIS (Moderate Resolution Imaging Spectroradiometer) are complemented with high spatial resolution data (ASTER, or Advanced Spaceborne Thermal Emission and Reflection Radiometer, and similar sensors) to document volcanic activity throughout the region during the period 2000–10. Five volcanoes were observed in eruption (Mount Erebus, Mount Belinda, Mount Michael, Heard Island and McDonald Island), which were predominantly low-level and effusive in nature. Mount Belinda produced tephra, building a cinder cone in addition to an extensive lava field. Five volcanoes exhibited detectable thermal, and presumed fumarolic, activity (Deception, Zavodovski, Candlemas, Bristol, and Bellingshausen islands). A minor eruption reported at Marion Island was not detected in our survey due to its small size. This study also discovered a new active vent on Mount Michael, tracked dramatic vent enlargement on Heard Island, and provides an improved picture of the morphology of some of the volcanoes.
10
Monjoie, Philippe, Henriette Lapierre, Artan Tashko, Georges H. Mascle, Aline Dechamp, Bardhyl Muceku, and Pierre Brunet. "Nature and origin of the Triassic volcanism in Albania and Othrys: a key to understanding the Neotethys opening?" Bulletin de la Société Géologique de France 179, no. 4 (July 1, 2008): 411–25. http://dx.doi.org/10.2113/gssgfbull.179.4.411.
Abstract:
AbstractTriassic volcanic rocks, stratigraphically associated with pelagic or reef limestones, are tectonically juxtaposed with Mesozoic ophiolites in the Tethyan realm. From the central (Dinarides, Hellenides) and eastern Mediterranean (Antalya, Troodos, Baër Bassit) to the Semail nappes (Oman), they occur either associated to the tectonic sole of the ophiolitic nappes or as a distinct tectonic pile intercalated between the ophiolites and other underthrust units. In the Dinaro-Hellenic belt, the Pelagonian units represent the lower plate, which is underthrust beneath the ophiolites. Middle to Late Triassic volcanic sequences are interpreted as the eastern flank of the Pelagonian platform and are therefore considered as a distal, deep-water part of the Pelagonian margin.The Triassic volcanics from Albania and Othrys are made up of basaltic pillowed and massive flows, associated locally with dolerites and trachytes. New elemental, Nd and Pb isotopic data allow to recognize four types of volcanic suites: (1) intra-oceanic alkaline and tholeiitic basalts, (2) intra-oceanic arc-tholeiites, (3) back-arc basin basalts, (4) calc-alkaline mafic to felsic rocks. Nd and Pb isotopic initial ratios suggest that the within-plate volcanic rocks were derived from an enriched oceanic island basalt type mantle source, devoid of any continental crustal component. The lower εNd value of the trachyte could be due to assimilation of oceanic altered crust or sediments in a shallow magma chamber. Island arc tholeiites and back-arc basin basalts have a similar wide range of εNd. The absence of Nb negative anomalies in the back-arc basin basalts suggests that the basin floored by these basalts was wide and mature. The high Th contents of the island arc tholeiites suggest that the arc volcanoes were located not far away from the continental margin.Albania and Othrys volcanics contrast with the Late Triassic volcanism from eastern Mediterranean (SW Cyprus, SW Turkey), which displays solely features of oceanic within plate suites. The presence of back-arc basin basalts associated with arc-related volcanics in Central Mediterranean indicates that they were close to a still active subduction during the Upper Triassic, while back-arc basins developed, associated with within-plate volcanism, leading to the NeoTethys opening.
11
Romanyuk, Fedor A. "Volcanological and geoecological studies on Iturup Island (Kuril Islands) in 2023." Geosystems of Transition Zones 8, no. 1 (March 2024): 56–63. http://dx.doi.org/10.30730/gtrz.2024.8.1.056-063.
Abstract:
Some preliminary results of the field work of the Institute of Marine Geology and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, on Iturup Island in 2023 are presented. The data on the modern volcanic activity of Machekha Crater of Tebenkov Volcano are provided. The data on the activity of Berutarube Volcano available in the literature have been supplemented. The data characterizing the current activity of Tebenkov and Berutarube Volcanoes have been obtained. Samples of thermal waters, hydrothermally altered rocks, and products of solfataric activity have been collected, and their thermal imaging has been performed. During the monitoring work, the waters of the thermal springs of the Dachnoe deposit have been sampled. In order to evaluate the impact of volcanism on the formation and development of the bryoflora and lichen flora of the south of Iturup Island, representatives of lichens and bryophytes have been collected on the slopes of Berutarube Volcano.
12
Smellie, John L., and Adam P. Martin. "Chapter 5.2a Erebus Volcanic Province: volcanology." Geological Society, London, Memoirs 55, no. 1 (2021): 415–46. http://dx.doi.org/10.1144/m55-2018-62.
Abstract:
AbstractThe Erebus Volcanic Province is the largest Neogene volcanic province in Antarctica, extendingc.450 km north–south and 170 km wide east–west. It is dominated by large central volcanoes, principally Mount Erebus, Mount Bird, Mount Terror, Mount Discovery and Mount Morning, which have sunk more than 2 km into underlying sedimentary strata. Small submarine volcanoes are also common, as islands and seamounts in the Ross Sea (Terror Rift), and there are many mafic scoria cones (Southern Local Suite) in the Royal Society Range foothills and Dry Valleys. The age of the volcanism ranges betweenc.19 Ma and present but most of the volcanism is <5 Ma. It includes active volcanism at Mount Erebus, with its permanent phonolite lava lake. The volcanism is basanite–phonolite/trachyte in composition and there are several alkaline petrological lineages. Many of the volcanoes are pristine, predominantly formed of subaerially erupted products. Conversely, two volcanoes have been deeply eroded. That at Minna Hook is mainly glaciovolcanic, with a record of the ambient mid–late Miocene eruptive environmental conditions. By contrast, Mason Spur is largely composed of pyroclastic density current deposits, which accumulated in a large mid-Miocene caldera that is now partly exhumed.
13
Mutaqin, Bachtiar W., Warsini Handayani, Fredi Satya Candra Rosaji, Desy Wahyuningtyas, and Muh Aris Marfai. "GEOMORPHOLOGICAL ANALYSIS FOR THE IDENTIFICATION OF SMALL VOLCANIC ISLANDS IN NORTH MALUKU, INDONESIA." JURNAL GEOGRAFI 13, no. 2 (July 21, 2021): 184. http://dx.doi.org/10.24114/jg.v13i2.21526.
Abstract:
Indonesia, which is located in the Pacific Ring of Fire, has at least 100 active volcanoes that are spread among more than 17,000 islands. Several active volcanoes are located on small islands, so they require a greater effort in relation to disaster management, especially those related to volcano activities. However, research on the identification of small volcanic islands has not been widely carried out in Indonesia. This study tries to fill the gap using a geomorphological aspect approach, which consists of morphology, morphogenesis, morphochronology, and morphoaransement, to identify small volcanic islands in North Maluku Province. Literature review and spatial data collection were carried out to determine the parameters used in the identification of small volcanic islands. Based on the literature review, this study uses 5 (five) parameters, namely the island area, the type of material, the location / morphoaransement, the pattern of river flow, and the features of the landforms which include the presence of volcanic landform (morphochronology), slope, and morphology. Based on the spatial analysis using these 5 parameters, information is obtained that there are at least 6 of the 17 islands that meet the criteria to be called small volcanic islands in North Maluku. Data on small volcanic islands and their characteristics are important information to educate the public and improve preparedness.Keywords: morphology, morphogenesis, morphochronology, morphoaransement, small volcanic islands
14
Clarkson, Bruce D., Beverley R. Clarkson, and James O. Juvik. "Pattern and process of vegetation change (succession) on two northern New Zealand island volcanoes." Surtsey research 13 (2015): 45–48. http://dx.doi.org/10.33112/surtsey.13.5.
Abstract:
Pattern and process of vegetation change (succession) were compared on two northern North Island volcanoes: Whakaari (White Island) and Rangitoto Island where the endemic woody tree Metrosideros excelsa is the primary colonizer of raw volcanic substrates. Quantitative data from our previous publications (see References) and the references therein illustrate sequences of vegetation succession following significant volcanic eruptions. New information on Rangitoto Island M. excelsa patch dynamics and updated vascular species statistics for Whakaari have also been included. We also draw on supporting data from M. excelsa forest on the mainland and long-inactive volcanic islands in the Bay of Plenty, to provide a context for understanding the vegetation dynamics on Whakaari and Rangitoto Island. Species facilitation, light availability, humidity, substrate and disturbance history are all key determinants of vegetation succession across these volcanic landscapes.
15
Buff, L., M. G. Jackson, K. Konrad, J. G. Konter, M. Bizimis, A. Price, E. F. Rose-Koga, J. Blusztajn, A. A. P. Koppers, and Santiago Herrera. "“Missing links” for the long-lived Macdonald and Arago hotspots, South Pacific Ocean." Geology 49, no. 5 (January 12, 2021): 541–44. http://dx.doi.org/10.1130/g48276.1.
Abstract:
Abstract The Cook-Austral volcanic lineament extends from Macdonald Seamount (east) to Aitutaki Island (west) in the South Pacific Ocean and consists of hotspot-related volcanic islands, seamounts, and atolls. The Cook-Austral volcanic lineament has been characterized as multiple overlapping, age-progressive hotspot tracks generated by at least two mantle plumes, including the Arago and Macdonald plumes, which have fed volcano construction for ∼20 m.y. The Arago and Macdonald hotspot tracks are argued to have been active for at least 70 m.y. and to extend northwest of the Cook-Austral volcanic lineament into the Cretaceous-aged Tuvalu-Gilbert and Tokelau Island chains, respectively. Large gaps in sampling exist along the predicted hotspot tracks, complicating efforts seeking to show that the Arago and Macdonald hotspots have been continuous, long-lived sources of hotspot volcanism back into the Cretaceous. We present new major- and trace-element concentrations and radiogenic isotopes for three seamounts (Moki, Malulu, Dino) and one atoll (Rose), and new clinopyroxene 40Ar/39Ar ages for Rose (24.81 ± 1.02 Ma) and Moki (44.53 ± 10.05 Ma). All volcanoes are located in the poorly sampled region between the younger Cook-Austral and the older, Cretaceous portions of the Arago and Macdonald hotspot tracks. Absolute plate motion modeling indicates that the Rose and Moki volcanoes lie on or near the reconstructed traces of the Arago and Macdonald hotspots, respectively, and the 40Ar/39Ar ages for Rose and Moki align with the predicted age progression for the Arago (Rose) and Macdonald (Moki) hotspots, thereby linking the younger Cook-Austral and older Cretaceous portions of the long-lived (>70 m.y.) Arago and Macdonald hotspot tracks.
16
TAKASHIMA, REISHI, HIROSHI NISHI, and TAKEYOSHI YOSHIDA. "Late Jurassic–Early Cretaceous intra-arc sedimentation and volcanism linked to plate motion change in northern Japan." Geological Magazine 143, no. 6 (September 4, 2006): 753–70. http://dx.doi.org/10.1017/s001675680600255x.
Abstract:
The Sorachi Group, composed of Upper Jurassic ophiolite and Lower Cretaceous island-arc volcano-sedimentary cover, provides a record of Late Jurassic–Early Cretaceous sedimentation and volcanism in an island-arc setting off the eastern margin of the Asian continent. Stratigraphic changes in the nature and volume of the Sorachi Group volcanic and volcaniclastic rocks reveal four tectonic stages. These stages resulted from changes in the subduction direction of the Pacific oceanic plate. Stage I in the Late Jurassic was characterized by extensive submarine eruptions of tholeiitic basalt from the back-arc basin. Slab roll-back caused rifting and sea-floor spreading in the supra-subduction zone along the active Asian continental margin. Stage II corresponded to the Berriasian and featured localized trachyandesitic volcanism that formed volcanic islands with typical island-arc chemical compositions. At the beginning of this stage, movement of the Pacific oceanic plate shifted from northeastward to northwestward. During Stage III, in the Valanginian, submarine basaltic volcanism was followed by subsidence. The Pacific oceanic plate motion turned clockwise, and the plate boundary between the Asian continent and the Pacific oceanic plate changed from convergent to transform. During Stage IV in the Hauterivian–Barremian, in situ volcanism ceased in the Sorachi–Yezo basin, and the volcanic front migrated west of the Sorachi–Yezo basin.
17
Le Pera, Emilia, Consuele Morrone, José Arribas, M. Eugenia Arribas, Eumenio Ancochea, and M. José Huertas. "Petrography and provenance of beach sands from volcanic oceanic islands: Cabo Verde, Atlantic Ocean." Journal of Sedimentary Research 91, no. 1 (January 31, 2021): 92–115. http://dx.doi.org/10.2110/jsr.2020.096.
Abstract:
ABSTRACT Volcaniclastic deposits have been extensively analyzed in several settings in the Pacific and circum-Pacific area. Recent volcaniclastic products from Atlantic oceanic islands offer another opportunity to add new data and be an important key to a better understanding of volcanic imprints on the sedimentary record. The Cabo Verde archipelago is an Atlantic Oceanic plateau with late Oligocene to Holocene volcanism. Outcrops consist mainly of mafic and strongly alkaline and ultra-alkaline volcanic (pyroclastic and lava flows) and less abundant intrusive rocks with minor carbonatites and carbonate sedimentary rocks, constituting a multiple-provenance assemblage for the sandy beaches surrounding the islands. Currently, climate is semiarid to hyperarid with ephemeral and intermittent streams. Thirty-six samples of beach sand from six principal Cabo Verde Islands were selected for petrographic inspection. On average, beach sands constitute a volcanolithic petrofacies. A relative increase in carbonate limeclasts and bioclasts dilutes the pure volcaniclastic contribution mainly on the older island beaches (Sao Vicente, Sal, and Boa Vista). The major components of Cabo Verde beach sands are highly variable; in general, composition is a function of island morphological evolution and age. Thus, beaches of the younger islands (Sao Nicolau, Santiago, and Fogo) consist mainly of volcanic lithic fragments, and monomineralic grains of dense minerals such as olivine, pyroxene, and amphibole, and single grains of plagioclase and anorthoclase. By contrast, beaches of older eastern islands (Sal, Boa Vista, and Sao Vicente) contain more calcareous bioclasts, micritic and/or sparitic sedimentary lithic grains. The presence of carbonate grains suggests provenance from shallow carbonate platforms developed during periods of volcanic quiescence. Cabo Verde volcanic sandy fractions are composed mostly of black, brown, and orange glassy volcanic particles exhibiting microlitic, lathwork, and vitric textures. Volcanic particles with lathwork textures are linked to mafic provenance assemblages (nephelinites, basanites, and tephrites). The content of glassy particles is nearly constant in all beaches, and both hydroclastic and epiclastic processes are reflected in these populations of glassy grains. Boa Vista, Sao Vicente, and Santiago beaches contain higher proportions of sideromelane, linked to recent coastal volcanism, and lower proportions of orange and black glassy particles. The concentration of orange glass particles in the beaches of Santiago Island is higher than in the other island beaches. These orange glassy textures have been preserved even if they were sourced from the intensely altered Ancient Eruptive Complex, representing the pre-Miocene seamount stage of Santiago Island. A very small percentage of altered labile monocrystalline grains such as olivine and the paucity of altered volcanic components reflect the weathering-limited erosion regime of the islands. The exposed phonolitic lava flows that occupy only a minor surface part of the inland source produce particles with microlitic texture in sand beaches. Thus, this texture is not exclusive to andesitic, basaltic, and basaltic andesites sources, suggesting the need for a review of these particles as source-sensitive provenance signals.
18
Pointon, Michael A., Michael J. Flowerdew, Peter Hülse, Simon Schneider, and Martin J. Whitehouse. "Mixed local and ultra-distal volcanic ash deposition within the Upper Cretaceous Kanguk Formation, Sverdrup Basin, Canadian Arctic Islands." Geological Magazine 156, no. 12 (June 18, 2019): 2067–84. http://dx.doi.org/10.1017/s0016756819000414.
Abstract:
AbstractThe Upper Cretaceous Kanguk Formation of the Sverdrup Basin, Canadian Arctic Islands, contains numerous diagenetically altered volcanic ash layers (bentonites). Eleven bentonites were sampled from an outcrop section on Ellesmere Island for U–Pb zircon secondary ion mass spectrometry dating and whole-rock geochemical analysis. Two distinct types of bentonite are identified from the geochemical data. Relatively thick (0.1 to 5 m) peralkaline rhyolitic to trachytic bentonites erupted in an intraplate tectonic setting. These occur throughout the upper Turonian to lower Campanian (c. 92–83 Ma) outcrop section and are likely associated with the alkaline phase of the High Arctic Large Igneous Province. Two thinner (<5 cm) subalkaline dacitic to rhyolitic bentonites of late Turonian to early Coniacian age (c. 90–88 Ma) are also identified. The geochemistry of these bentonites is consistent with derivation from volcanoes within an active continental margin tectonic setting. The lack of nearby potential sources of subalkaline magmatism, together with the thinner bed thickness of the subalkaline bentonites and the small size of zircon phenocrysts therein (typically 50–80 μm in length) are consistent with a more distal source area. The zircon U–Pb age and whole-rock geochemistry of these two subalkaline bentonites correlate with an interval of intense volcanism in the Okhotsk–Chukotka Volcanic Belt, Russia. It is proposed that during late Turonian to early Coniacian times intense volcanism within the Okhotsk–Chukotka Volcanic Belt resulted in widespread volcanic ash dispersal across Arctic Alaska and Canada, reaching as far east as the Sverdrup Basin, more than 3000 km away.
19
Valente, Luis M., Rampal S. Etienne, and Albert B. Phillimore. "The effects of island ontogeny on species diversity and phylogeny." Proceedings of the Royal Society B: Biological Sciences 281, no. 1784 (June 7, 2014): 20133227. http://dx.doi.org/10.1098/rspb.2013.3227.
Abstract:
A major goal of island biogeography is to understand how island communities are assembled over time. However, we know little about the influence of variable area and ecological opportunity on island biotas over geological timescales. Islands have limited life spans, and it has been posited that insular diversity patterns should rise and fall with an island's ontogeny. The potential of phylogenies to inform us of island ontogenetic stage remains unclear, as we lack a phylogenetic framework that focuses on islands rather than clades. Here, we present a parsimonious island-centric model that integrates phylogeny and ontogeny into island biogeography and can incorporate a negative feedback of diversity on species origination. This framework allows us to generate predictions about species richness and phylogenies on islands of different ages. We find that peak richness lags behind peak island area, and that endemic species age increases with island age on volcanic islands. When diversity negatively affects rates of immigration and cladogenesis, our model predicts speciation slowdowns on old islands. Importantly, we find that branching times of in situ radiations can be informative of an island's ontogenetic stage. This novel framework provides a quantitative means of uncovering processes responsible for island biogeography patterns using phylogenies.
20
Allen, Claire S., and John L. Smellie. "Volcanic features and the hydrological setting of Southern Thule, South Sandwich Islands." Antarctic Science 20, no. 3 (May 19, 2008): 301–8. http://dx.doi.org/10.1017/s0954102008001156.
Abstract:
AbstractThis paper provides new observations of volcanic features and hydrological characteristics in and around Southern Thule, the southernmost group of islands in the South Sandwich Islands, including the first high-resolution bathymetric image of the Douglas Strait caldera. The South Sandwich Islands are the summits of several very large subduction-related volcanoes constructed at the eastern boundary of the Scotia Sea. Observations of the islands are scarce owing to their remote location and they are only rarely visited, yet the area is an active volcanic arc that is rapidly changing as a result of eruptions, including one (on Montagu Island) that has been ongoing for six years and is creating new land. The three islands that make up Southern Thule are morphologically different, and they illustrate different stages in the construction and evolution of islands in the South Sandwich group. We present the results of an acoustic and hydrographic survey that resulted in the first high-resolution, multibeam ‘swath’ image of the submarine Douglas Strait caldera. The results confirm the presence of a large sediment mound (c. 1000 m3 in volume) on the floor of the Douglas Strait caldera related to a flank collapse of Thule Island. The image also shows an extensive arcuate fault structure, interpreted as evidence that the caldera is nested, and its geomorphological freshness suggests that it is a very young feature that formed conceivably in the last few decades or centuries. The bathymetric image also reveals at least three cone- or mound-like structures within the caldera that may relate to renewed post-caldera volcanism (as pyroclastic cones and/or pillow mounds). Recently formed cones and faults associated with caldera rims are often associated with hydrothermal activity. However, temperature and salinity data collected within the caldera do not yet show any evidence of hydrothermal venting. The ocean surrounding Southern Thule has a prominent surface layer of low salinity water that is probably caused by a high meltwater flux derived from ice caps on the islands. This flux may have been enhanced by the recent warming trend observed in the Antarctic Peninsula, although volcano-related geothermal melting in the ice-filled Thule Island caldera may also contribute to the meltwater flux.
21
Pranata, Bayu, Mohamad Ramdhan, Muhammad Hanif, Muhammad Iqbal Sulaiman, Mufti Putra Maulana, Wandono Wandono, Sri Widiyantoro, et al. "SEISMIC IMAGING BENEATH SUMATRA ISLAND AND ITS SURROUNDINGS, INDONESIA, FROM LOCAL-REGIONAL P-WAVE EARTHQUAKE TOMOGRAPHY." Rudarsko-geološko-naftni zbornik 38, no. 3 (2023): 119–32. http://dx.doi.org/10.17794/rgn.2023.3.10.
Abstract:
Sumatra Island and its surroundings, Indonesia, are one of the most active tectonics in the world. The Aceh-Andaman earthquake, one of the most destructive earthquakes in the world, occurred there. It has attracted many earth scientists to apply various methods, including seismic tomography, to understand the island’s subsurface structure and tectonic system. This study is the first to delineate subsurface imaging beneath the island and its surroundings using a local-regional earthquake catalogue from the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG) seismicnetwork. The tomographic imaging of P-wave (Vp) conducted in this study has successfully delineated subduction slabs (high Vp), partial melting zones (low Vp), volcanic arcs (low Vp), and Sumatran Fault zones (low Vp). The relationship between the subduction zone and the volcanic arc on the island can be seen on several vertical sections where a partial melting zone occurs at a depth of about 100 km, which functions as magma feeding for some volcanoes on the island. The oceanic slab model also exhibits a more pronounced and steeper slope towards the southern regions of Sumatra Island, possibly attributed to the slab’s aging process in that direction. The results highlight the importance of the BMKG seismic network in imaging local-regional subsurface structures beneath Indonesia’s archipelago, especially for the main islands such as Sumatra.
22
Putranto, M. H. R., I. Meilano, R. Virtriana, M. Abdurrachman, and R. F. Adiwijaya. "SPATIAL ANALYSIS OF VOLCANIC ASH DISTRIBUTION DUE TO VOLCANIC ERUPTION IN JAVA ISLAND." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLVIII-M-3-2023 (September 5, 2023): 197–202. http://dx.doi.org/10.5194/isprs-archives-xlviii-m-3-2023-197-2023.
Abstract:
Abstract. Indonesia is located on the Ring of Fire with the most geologically active than any other countries, which makes it vulnerable due to the massive earthquakes and volcanic eruptions. Java Island has the most active volcano with high risks such as human risk and infrastructure from volcanic ash because of volcanic eruptions. The availability of the map of potential volcanic hazards is important to help mitigate the risk caused by volcanic eruptions. However, to the best of the author's knowledge, the distribution of volcanic ash has never been assessed in detail in the disaster-prone hazard map published by the Centre for Volcanology and Geological Hazard Mitigation (CVGHM), Indonesia. This research reported the potential distribution of volcanic ash due to volcanic eruptions in the future in Java island. Following the principles of Probabilistic Hazard Assessment and TephraProb software, the modeling of volcanic ash potential was performed using various parameters such as historical data, eruption source parameter, total grain-size distribution, tephra2 parameter, and the wind speed around the volcanoes as an input. The map shows the distribution of volcanic ash based on the volcanic ash accumulation (kg/m2) and the volcanic ash hazard map is classified into three classes. There are 19 models of volcanic ash distribution with various probabilities of exceedance based on 19 A-type volcanoes on Java Island. This volcano's distribution of volcanic ash tends to the southwest as the wind speed and direction.
23
Koloskov, A. V., M. Yu Puzankov, V. V. Ananiev, and D. V. Kovalenko. "BOLSHOI PAYALPAN VOLCANO (SREDINNY RANGE, KAMCHATKA). PROBLEMATIC ASPECTS OF CONVERGENCE OF ISLAND-ARC AND INTRAPLATE PETROLOGICAL AND GEOCHEMICAL SIGNATURES IN THE MAGMATIC SYSTEM." Tikhookeanskaya Geologiya 41, no. 2 (2022): 3–24. http://dx.doi.org/10.30911/0207-4028-2022-41-2-3-24.
Abstract:
The paper presents the data on age, mineralogy, geochemistry, and isotope composition of rocks from the Bolshoi Payalpan Volcano (Sredinny Range, Kamchatka). We compared these data with those on the Nosichan and Belogolovsky volcanoes, located within the Belogolovsky volcanic center. The basalts of the neck and the upper lava complex of Bolshoi Payalpan are compositionally similar to the intraplate-type trachybasalts of the Belogolovsky Volcano, and the basaltic andesites of the lower lava and the cone complex are similar to the island arc rocks of the Nosichan Volcano. Analysis of the data obtained evidences that spatial and temporal manifestations of intraplate and island-arc volcanism at the Bolshoi Payalpan Volcano are not accidental, but may be a consequence of a change in the degree and depth of melting of the same deep source with the involvement of a mantle diapir. The Belogolovsky volcanic center formed in a setting of the Late Miocene-Early Pliocene rifting. Its evolution, right up to its extinction, proceeded in the same geodynamic setting with an increase in depth of the mantle source and a decrease in the degree of its melting. Rock compositions of the Lower-Middle Pliocene Nosichan Volcano remain of the island-arc type under conditions of rifting, since they are associated with the mantle reservoir located at a shallower depth, which has experienced a higher degree of melting. There is good reason for considering large volcanic centers as spontaneously-developing geological entities. As the endogenous activity dies down, the degree of melting decreases and the depth of melting increases with the replacement of island-arc volcanism by intraplate volcanism. The volcanic center becomes extinct.
24
Fourré, Elise, Patrick Allard, Philippe Jean-Baptiste, Dario Cellura, and Francesco Parello. "H3e/H4e Ratio in Olivines from Linosa, Ustica, and Pantelleria Islands (Southern Italy)." Journal of Geological Research 2012 (March 1, 2012): 1–8. http://dx.doi.org/10.1155/2012/723839.
Abstract:
We report helium isotope data for 0.03–1 Ma olivine-bearing basaltic hawaiites from three volcanoes of the southern Italy magmatic province (Ustica, Pantelleria, and Linosa Islands). Homogenous H3e/H4e ratios (range: 7.3–7.6 Ra) for the three islands, and their similarity with the ratio of modern volcanic gases on Pantelleria, indicate a common magmatic end-member. In particular, Ustica (7.6±0.2 Ra) clearly differs from the nearby Aeolian Islands Arc volcanism, despite its location on the Tyrrhenian side of the plate boundary. Although limited in size, our data set complements the large existing database for helium isotope in southern Italy and adds further constraints upon the spatial extent of intraplate alkaline volcanism in southern Mediterranea. As already discussed by others, the He-Pb isotopic signature of this magmatic province indicates a derivation from a mantle diapir of a OIB-type that is partially diluted by the depleted upper mantle (MORB mantle) at its periphery.
25
SURIN, TIMOTHEY. "Paleovolcanism of the eastern Magnitogorsk megazone, Southern Urals: Petrology, geochemistry, and gold-bearing perspectives." Domestic geology, no. 5 (November 22, 2023): 72–94. http://dx.doi.org/10.47765/0869-7175-2023-10024.
Abstract:
The geological-petrographic and petrogeochemical features of volcanic rocks are considered of the Gumbeika zone in the Southern Urals, that is the frontal easternmost portion of the East Magnitogorsk paleo-island arc. The volcanites are united into the Gumbeika volcanic association. The association is shown to be represented by the basalt– andesite–dacite–rhyodacite “uninterrupted” homodrom igneous series. The compositional features of the volcanics allow confident assigning them to the island-arc calc-alkaline series, or more precisely, to formations of “developed” island arcs. It is concluded that the main process that determines the general appearance and composition of the unified petrogenetic series of rocks of the Gumbeika association was the fractional crystallization of the parental basaltic melts in deep-seated chambers and, then, in near-surface peripheral ones. The emplacement of some of the magmatic bodies was also accompanied by in situ gravitational differentiation. The general similarity of the volcanics-associated gold-silver deposits with the analogs within recent island arcs allows us to suggest a great perspectives for gold-silver mineralization throughout the Gumbeika zone. Two forecasted ore fields have been identified.
26
Valadão, P., J. L. Gaspar, G. Queiroz, and T. Ferreira. "Landslides density map of S. Miguel Island, Azores archipelago." Natural Hazards and Earth System Sciences 2, no. 1/2 (June 30, 2002): 51–56. http://dx.doi.org/10.5194/nhess-2-51-2002.
Abstract:
Abstract. The Azores archipelago is located in the Atlantic Ocean and is composed of nine volcanic islands. S. Miguel, the largest one, is formed by three active, E-W trending, trachytic central volcanoes with caldera (Sete Cidades, Fogo and Furnas). Chains of basaltic cinder cones link those major volcanic structures. An inactive trachytic central volcano (Povoação) and an old basaltic volcanic complex (Nordeste) comprise the easternmost part of the island. Since the settlement of the island early in the 15th century, several destructive landslides triggered by catastrophic rainfall episodes, earthquakes and volcanic eruptions occurred in different areas of S. Miguel. One unique event killed thousands of people in 1522. Houses and bridges were destroyed, roads were cut, communications, water and energy supply systems became frequently disrupted and areas of fertile land were often buried by mud. Based on (1) historical documents, (2) aerial photographs and (3) field observations, landslide sites were plotted on a topographic map, in order to establish a landslide density map for the island. Data obtained showed that landslide hazard is higher on (1) the main central volcanoes where the thickness of unconsolidated pyroclastic deposits is considerable high and (2) the old basaltic volcanic complex, marked by deep gullies developed on thick sequences of lava flows. In these areas, caldera walls, fault scarps, steep valley margins and sea cliffs are potentially hazardous.
27
Cole, J. W., C. E. Sabel, E. Blumenthal, K. Finnis, A. Dantas, S. Barnard, and D. M. Johnston. "GIS-based emergency and evacuation planning for volcanic hazards in New Zealand." Bulletin of the New Zealand Society for Earthquake Engineering 38, no. 3 (September 30, 2005): 149–64. http://dx.doi.org/10.5459/bnzsee.38.3.149-164.
Abstract:
Geographic Information Systems (GIS) provide a range of techniques which allow ready access to data, and the opportunity to overlay graphical location-based information for ease of interpretation. They can be used to solve complex planning and management problems. All phases of emergency management (reduction, readiness, response and recovery) can benefit from GIS, including applications related to transportation systems, a critical element in managing effective lifelines in an emergency. This is particularly true immediately before and during a volcanic eruption.
The potential for volcanic activity in New Zealand is high, with 10 volcanoes or volcanic centres (Auckland, Bay of Islands, Haroharo, Mayor Island, Ruapehu, Taranaki, Tarawera, Taupo, Tongariro (including Ngauruhoe) and White Island) recognised as active or potentially active. In addition there are many active and potentially active volcanoes along the Kermadec Island chain. There is a great deal of background information on all of these volcanoes, and GIS is currently being used for some aspects of monitoring (e.g. ERS and Envisat radar interferometry for observing deformation prior to eruptions). If an eruption is considered imminent, evacuation may be necessary, and hence transportation systems must be evaluated. Scenarios have been developed for many centres (e.g. Taranaki/Egmont and Bay of Plenty volcanoes), but so far the use of GIS in planning for evacuation is limited.
This paper looks at the use of GIS, indicates how it is being used in emergency management, and suggests how it can be used in evacuation planning.
28
Heusser, Calvin J. "Late Quaternary vegetation of the Aleutian Islands, southwestern Alaska." Canadian Journal of Botany 68, no. 6 (June 1, 1990): 1320–26. http://dx.doi.org/10.1139/b90-168.
Abstract:
Late Quaternary vegetational history of the Aleutian Islands is interpreted from fossil pollen and spore stratigraphy and radiocarbon chronology of sections of mires on the islands of Attu, Adak, Atka, and Umnak. Mires postdate the withdrawal of ice-age glaciers between approximately 12 000 and 10 000 years ago with the exception of the mire on Attu Island, where deglaciation apparently began as late as 7000 years ago. No uniform pattern of change in Pacific coastal tundra communities is evident in the fossil assemblages. Pollen assemblages, consisting variably of Gramineae, Cyperaceae, Empetrum, Umbelliferae, Salix, Ranunculaceae, Compositae, Polypodiaceae, and Lycopodium, reflect conditions in effect in different sectors of the Aleutian chain. Climate, soil, topography, volcanism, and seismic activity are noteworthy parameters influencing vegetation composition and distribution. Volcanism has been of major importance, as shown by thickness, distribution, and frequency of tephra layers that number 5 on Attu, 24 on Adak, 17 on Atka, and 5 on Umnak. A repeated condition of patch dynamics, created in the main by recurrent volcanic eruptions with widespread accompanying ashfalls, has apparently overprinted the effects of climatic change. Key words: Aleutian Islands, Quaternary, vegetation, fossil pollen, volcanism.
29
McDougall, Ian. "Retrospective on the plate tectonic revolution focusing on K/Ar dating, linear volcanic chains and the geomagnetic polarity time scale." Earth Sciences History 32, no. 2 (January 1, 2013): 313–31. http://dx.doi.org/10.17704/eshi.32.2.p775346702221163.
Abstract:
Notions of migration of volcanism in the Hawaiian Islands were contemplated for decades, but no quantitative measurements were made until the early 1960s. Collections of volcanic rocks from the accessible high islands were undertaken by the author in 1961. Surprisingly, K/Ar dating was possible, owing to much lower atmospheric argon in the samples than anticipated, allowing radiogenic argon to be detected. It became evident that there had been a progression of volcanism from Kauai (~4.4 Ma) in the WNW of the archipelago to the Island of Hawaii in the ESE, where there is active volcanism, with a rate of migration of volcanism averaging ~13-16 cm/year. These results gave strong support to J Tuzo Wilson's hotspot model for the origin of certain island chains, proposed in 1963. Later, rates determined in other Pacific island chains were concordant with Hawaii as indicators of direction and rate of plate motions. Concurrently with the successful Hawaiian age measurements, palaeomagnetic results were obtained by Don Tarling and combined with the K/Ar ages these showed that normal and reversed polarity zones were time related, and a geomagnetic polarity time scale was rapidly developed. Marine magnetic measurements across mid ocean ridges showed symmetry of parallel zones of magnetized crust, interpreted by Fred Vine and Drummond Matthews as reflecting normal and reversely magnetized new ocean floor, that was soon calibrated against the geomagnetic polarity time scale, providing persuasive evidence in favour of plate tectonics and seafloor spreading. But K/Ar dating was crucial to the major changes in tectonic hypotheses.
30
Fadda, S., M. Fiori, S. Pretti, and P. Valera. "MANGANESE MINERALISATIONS AT THE BASE OF MIOCENE SEDIMENTS IN NORTHERN SARDINIA (ITALY)." Bulletin of the Geological Society of Greece 43, no. 5 (July 31, 2017): 2588. http://dx.doi.org/10.12681/bgsg.11666.
Abstract:
During the eastward drift of the Palaeozoic-Mesozoic block formed by Sardinia and Corsica in the Oligocene-Miocene, calc-alkaline volcanism developed mostly in the western part of the island. Most Tertiary metallogenic phoenomena are related to hydrothermal activity associated with this volcanism. Following volcanic and related hydrothermal activity, sediments were deposited during the Oligocene-Miocene as a consequence of a marine transgression. The basal part of this series is clastic and includes elements derived from erosion of unaltered volcanics as well as hydrothermally altered rocks and hydrothermal vein quartz. Inside the Tertiary volcanics manganese ore-minerals occur as nodules, veinlets, and stockworks and mainly include Mn and Fe oxides; quartz in different forms is the most common gangue mineral. The mineralisations at the contact between volcanics and Miocene sediments are the most homogeneous, the ore-minerals occur in the cement, but also as fairly continuous thin beds, nodules and veinlets containing pyrolusite, frequent ramsdellite, less frequent manganite, psilomelane, cryptomelane-manjiroite, rare ranciéite, and todorokite. The nature of the ore-bearing beds indicate a near-shore clastic environment along the ancient coastal lines of the Miocene sea. Genetic considerations point to a supergenic transport and redeposition after erosion of primary dispersion and residual concentrations of Mn in the volcanics.
31
Timpa, Sean, Kathryn M. Gillis, and Dante Canil. "Accretion-related metamorphism of the Metchosin Igneous Complex, southern Vancouver Island, British Columbia." Canadian Journal of Earth Sciences 42, no. 8 (August 1, 2005): 1467–79. http://dx.doi.org/10.1139/e05-043.
Abstract:
The metamorphic history of the volcanic sequence of the Metchosin Igneous Complex (MIC), an Eocene ophiolite exposed on southern Vancouver Island, British Columbia, Canada, was studied to examine the roles of seafloor and accretion-related processes. Metamorphic facies in the volcanics vary from prehniteactinolite assemblages in the east to greenschist and amphibolite assemblages in the west. In the east, metamorphism is typified by chlorite ± prehnite ± epidote ± actinolite assemblages that fill vesicles and replace interstitial material; plagioclase is variably albitized, and clinopyroxene is relatively fresh. In the west, the common groundmass assemblage is amphibole + epidote ± chlorite. These assemblages and chlorite geothermometry show a regional eastwest gradient of ∼510 °C/km that is oblique to the volcanic stratigraphy. The regional metamorphic facies distribution for the MIC volcanics is not consistent with seafloor hydrothermal metamorphism documented for ocean crust from mid-ocean ridges, ocean islands, or island arcs. We speculate that underthrusting of the MIC beneath the Pacific Rim Terrane led to the regional metamorphism of the MIC, and that the change in metamorphic grade from east to west results from regional tilting of the complex, perhaps by orographic effects, during or after accretion.
32
Ebmeier, S. K., A. M. Sayer, R. G. Grainger, T. A. Mather, and E. Carboni. "Systematic satellite observations of the impact of aerosols from passive volcanic degassing on local cloud properties." Atmospheric Chemistry and Physics 14, no. 19 (October 9, 2014): 10601–18. http://dx.doi.org/10.5194/acp-14-10601-2014.
Abstract:
Abstract. The impact of volcanic emissions, especially from passive degassing and minor explosions, is a source of uncertainty in estimations of aerosol indirect effects. Observations of the impact of volcanic aerosol on clouds contribute to our understanding of both present-day atmospheric properties and of the pre-industrial baseline necessary to assess aerosol radiative forcing. We present systematic measurements over several years at multiple active and inactive volcanic islands in regions of low present-day aerosol burden. The time-averaged indirect aerosol effects within 200 km downwind of island volcanoes are observed using Moderate Resolution Imaging Spectroradiometer (MODIS, 2002–2013) and Advanced Along-Track Scanning Radiometer (AATSR, 2002–2008) data. Retrievals of aerosol and cloud properties at Kīlauea (Hawai'i), Yasur (Vanuatu) and Piton de la Fournaise (la Réunion) are rotated about the volcanic vent to be parallel to wind direction, so that upwind and downwind retrievals can be compared. The emissions from all three volcanoes – including those from passive degassing, Strombolian activity and minor explosions – lead to measurably increased aerosol optical depth downwind of the active vent. Average cloud droplet effective radius is lower downwind of the volcano in all cases, with the peak difference ranging from 2–8 μm at the different volcanoes in different seasons. Estimations of the difference in Top of Atmosphere upward Short Wave flux upwind and downwind of the active volcanoes from NASA's Clouds and the Earth's Radiant Energy System (CERES) suggest a downwind elevation of between 10 and 45 Wm−2 at distances of 150–400 km from the volcano, with much greater local (< 80 km) effects. Comparison of these observations with cloud properties at isolated islands without degassing or erupting volcanoes suggests that these patterns are not purely orographic in origin. Our observations of unpolluted, isolated marine settings may capture processes similar to those in the pre-industrial marine atmosphere.
33
Ramon, Patricio, Silvia Vallejo, Patricia Mothes, Daniel Andrade, Francisco Vásconez, Hugo Yepes, Silvana Hidalgo, and Santiago Santamaría. "Instituto Geofísico – Escuela Politécnica Nacional, the Ecuadorian Seismology and Volcanology Service." Volcanica 4, S1 (November 1, 2021): 93–112. http://dx.doi.org/10.30909/vol.04.s1.93112.
Abstract:
Ninety-eight Quaternary volcanoes have been identified in the Ecuadorian Andes and the Galápagos Islands, from them, nine experienced at least one eruption in the last twenty years. Additionally, about 35 % of the Ecuadorian population live in areas that could be affected by future volcanic eruptions. The Instituto Geofísico of the Escuela Politécnica Nacional (IG-EPN) monitors and evaluates Ecuador’s volcanic hazards: nineteen volcanic hazard maps and hundreds of related articles have been published as a result of its research. The monitoring networks include eighteen volcanoes, with more than 266 stations, which also form the basis for early warning systems at several volcanoes. Volcanic activity is widely communicated by the IG-EPN through periodic information published in different media (website and social networks). Ecuadorian volcanoes will erupt in the future and, therefore, the IGEPN continuously updates its monitoring and hazard assessment practices and improves communication channels and protocols to successfully fulfil its responsibilities. Noventa y ocho volcanes cuaternarios han sido identificados en los Andes ecuatorianos y Galápagos de los cuales nueve han experimentado erupciones al menos una vez en los últimos veinte años. Adicionalmente, alrededor del 35 % de la población ecuatoriana vive en zonas que podrían ser afectadas durante futuras erupciones. El Instituto Geofísico de la Escuela Politécnica Nacional (IG-EPN) monitorea y evalúa la amenaza volcánica del país y, como resultado de sus investigaciones, diecinueve mapas de amenaza volcánica y centenares de artículos científicos han sido publicados. Las redes de vigilancia comprenden dieciocho volcanes e incluyen más de 266 estaciones, que son parte también de los sistemas de alerta temprana. La actividad volcánica es comunicada amplia y periódicamente por el IG-EPN a través diferentes medios (página web y redes sociales). Comprendiendo que futuras erupciones ocurrirán en Ecuador, el IG-EPN continúa actualizando sus prácticas de vigilancia y evaluación de la amenaza, y mejorando sus protocolos de comunicación para cumplir exitosamente sus responsabilidades.
34
Rees, P. M., and J. L. Smellie. "Cretaceous angiosperms from an allegedly Triassic flora at Williams Point, Livingston Island, South Shetland Islands." Antarctic Science 1, no. 3 (September 1989): 239–48. http://dx.doi.org/10.1017/s0954102089000362.
Abstract:
A terrestrial sequence on Livingston Island, South Shetland Islands, known as the Williams Point Beds contains a well-preserved, diverse fossil flora previously assigned a Triassic age. Because of their supposed age, volcanic provenance and evidence for active volcanism, the Williams Point Beds have occupied a unique position in Gondwana (pre-Jurassic) stratigraphy in the Antarctic Peninsula region. However, a large new collection of plant specimens obtained at Williams Point has yielded several species of angiosperm leaves, which are abundant and occur at all levels within the Williams Point Beds sequence. Thus, a Triassic age is no longer tenable. On the basis of the plants present and published radiometric ages for associated strata, the Williams Point Beds fossil flora is reassigned to the Cretaceous, and there is some evidence for a more restricted Albian–Cenomanian age. This revision of the age of the Williams Point Beds removes all direct evidence for an active Triassic volcanic arc in the Antarctic Peninsula region.
35
Garcia, Sebastian, and Gabriela Badi. "Towards the development of the first permanent volcano observatory in Argentina." Volcanica 4, S1 (November 1, 2021): 21–48. http://dx.doi.org/10.30909/vol.04.s1.2148.
Abstract:
Argentina is a country that presents a complex situation regarding volcanic risk, where a total of 38 volcanoes are considered active. Although Argentina has no major cities close to these volcanoes, the continuous increase in economic activity and infrastructure near the Andean Codillera will increase exposure to volcano hazards in the future. Further, volcanic activity on the border between Argentina and Chile poses a unique challenge in relation to volcano monitoring and the management of volcanic emergencies. Additionally, due to atmospheric circulation patterns in the region (from West to East), Argentina is exposed to ashfall and ash dispersion from frequent explosive eruptions from Chilean volcanoes. Considering this, the Servicio Geológico Minero Argentino (SEGEMAR) decided to create and implement a Volcanic Threat Assessment Program, which includes the creation of the the first permanent volcano observatory for the country, the Observatorio Argentino de Vigilancia Volcánica (OAVV). Previously the Decepcion Island volcano observatory was created as a collaboration between the Instituto Antártico Argentino (IAA) and the Museo Nacional de Ciencias Naturales (MNCN) from the Consejo Superior de Investigaciones Científicas (CSIC). Argentina es un país que presenta una compleja situación con respecto al riesgo volcánico, donde un total de 38 volcanes son considerados activos. Aunque Argentina no tiene ciudades importantes cerca de estos volcanes, el continuo incremento de la actividad económica y la infraestructura cerca de la Cordillera de los Andes, generará en el futuro un aumento en la exposición a estos peligros. Además, la actividad volcánica en la frontera entre Argentina y Chile constituye un desafío único en relación con el monitoreo de volcanes y la gestión de emergencias volcánicas. Adicionalmente, debido a los patrones de circulación atmosférica en la región (desde el oeste hacia el este), Argentina está expuesta a la caída y dispersión de cenizas de las frecuentes erupciones explosivas de volcanes chilenos. Teniendo esto en cuenta, el Servicio Geológico Minero Argentino (SEGEMAR) decidió crear e implementar un programa de evaluación de amenazas volcánicas, que incluye, la creación del primer observatorio permanente de volcanes para el país, el Observatorio Argentino de Vigilancia Volcánica (OAVV). Previamente, el Observatorio Volcanológico de la Isla Decepción fue creado como una colaboración entre el Instituto Antártico Argentino (IAA) y el Museo Nacional de Ciencias Naturales (MNCN) del Consejo Superior de Investigaciones Científicas de España (CSIC).
36
Moretti, Sacha, Apostolos Salmatonidis, Xavier Querol, Antonella Tassone, Virginia Andreoli, Mariantonia Bencardino, Nicola Pirrone, Francesca Sprovieri, and Attilio Naccarato. "Contribution of Volcanic and Fumarolic Emission to the Aerosol in Marine Atmosphere in the Central Mediterranean Sea: Results from Med-Oceanor 2017 Cruise Campaign." Atmosphere 11, no. 2 (January 30, 2020): 149. http://dx.doi.org/10.3390/atmos11020149.
Abstract:
This work studied the contribution of the geogenic sources volcanoes and fumaroles to the aerosol in marine atmosphere in the central Mediterranean basin. For this purpose, in the framework of the Med-Oceanor measurement program, we carried out a cruise campaign in the summer of 2017 to investigate the impact to the aerosol of the most important Mediterranean volcanoes (Mount Etna, Stromboli Island, and Marsili Seamount) and solfatara areas (Phlegraean Fields complex, Volcano Islands, Ischia Island, and Panarea submarine fumarole). We collected PM10 and PM2.5 samples in 12 sites and performed chemical characterization to gather information about the concentration of major and trace elements, elemental carbon (EC), organic carbon (OC), and ionic species. The use of triangular plots and the calculation of enrichment factors confirmed the interception of volcanic plume. We integrated the outcomes from chemical characterization with the use of factor analysis and SEM/EDX analysis for the source apportionment. Anthropogenic and natural sources including shipping emissions, volcanic and fumarolic load, as well as sea spray were identified as the main factors affecting aerosol levels in the study area. Furthermore, we performed pattern recognition analysis by stepwise linear discriminant analysis to seek differences in the composition of PM10 and PM2.5 samples according to their volcanic or solfatara origin.
37
Hicks, A., J. Barclay, P. Simmons, and S. Loughlin. "An interdisciplinary approach to volcanic risk reduction under conditions of uncertainty: a case study of Tristan da Cunha." Natural Hazards and Earth System Sciences Discussions 1, no. 6 (December 23, 2013): 7779–820. http://dx.doi.org/10.5194/nhessd-1-7779-2013.
Abstract:
Abstract. This research project adopted an interdisciplinary approach to volcanic risk reduction on the remote volcanic island of Tristan da Cunha (South Atlantic). New data were produced that: (1) established no spatio-temporal pattern to recent volcanic activity; (2) quantified the high degree of scientific uncertainty around future eruptive scenarios; (3) analysed the physical vulnerability of the community as a consequence of their geographical isolation and exposure to volcanic hazards; (4) evaluated social and cultural influences on vulnerability and resilience. Despite their isolation and prolonged periods of hardship, islanders have demonstrated an ability to cope with and recover from adverse events. This resilience is likely a function of remoteness, strong kinship ties, bonding social capital, and persistence of shared values and principles established at community inception. While there is good knowledge of the styles of volcanic activity on Tristan, given the high degree of scientific uncertainty about the timing, size and location of future volcanism, a qualitative scenario planning approach was used as a vehicle to convey this information to the islanders. This deliberative, anticipatory method allowed on-island decision makers to take ownership of risk identification, management and capacity building within their community. This paper demonstrates the value of integrating social and physical sciences with development of effective, tailored communication strategies in volcanic risk reduction.
38
Kinvig, H. S., A. Winson, and J. Gottsmann. "Analysis of volcanic threat from Nisyros Island, Greece, with implications for aviation and population exposure." Natural Hazards and Earth System Sciences 10, no. 6 (June 7, 2010): 1101–13. http://dx.doi.org/10.5194/nhess-10-1101-2010.
Abstract:
Abstract. Nisyros island in the South Aegean volcanic arc, Greece, is a Quaternary composite volcano with a 3.8 km wide caldera that in 1996 entered a volcano-seismic crisis, which heralded the islands' return to a state of unrest. The caldera has been the locus of at least thirteen phreatic eruptions in historical times, the most recent in 1888, and the system is still presently affected by considerable hydrothermal activity. Although the recent unrest waned off without eruption, there are still open questions relating to the current threat of volcanic activity from the island. Here, we perform a detailed and systematic assessment of the volcanic threat of Nisyros using a threat analysis protocol established as part of the USGS National Volcano Early Warning System (NVEWS). The evaluation involves a methodical assessment of fifteen hazard and exposure factors, and is based on a score system, whereby the higher the score, the higher the threat is. Uncertainty in assessment criteria are expressed by allowing for a conservative and an extreme score for each factor. We draw our analysis from published data as well as from results of our research on Nisyros over the past years. Our analysis yields a conservative threat score of 163 and an extreme score of 262. The most adverse exposure factors include significant scores relating to aviation and population exposure to volcanic hazards from Nisyros. When looked at in comparison to US volcanoes both scores place Nisyros in the "Very High Threat (VHT)" category, grouping it with volcanoes such as Redoubt, Mount Ranier and Crater Lake. We identify a short-fall in recommended surveillance efforts for VHT volcanoes given existing monitoring capabilities on the island. We discuss potential pitfalls of applying the NVEWS scheme to Nisyros and suggest potential adaptation of analysis scheme to match industrial and societal conditions in Europe. At the same time, our findings indicate that that volcanic threat posed by Nisyros volcano may currently be underestimated.
39
Phillips, Thomas B., and Craig Magee. "Structural controls on the location, geometry and longevity of an intraplate volcanic system: the Tuatara Volcanic Field, Great South Basin, New Zealand." Journal of the Geological Society 177, no. 5 (June 5, 2020): 1039–56. http://dx.doi.org/10.1144/jgs2020-050.
Abstract:
Intraplate volcanism is widely distributed across the continents, but the controls on the 3D geometry and longevity of individual volcanic systems remain poorly understood. Geophysical data provide insights into magma plumbing systems, but, as a result of the relatively low resolution of these techniques, it is difficult to evaluate how magma transits highly heterogeneous continental interiors. We use borehole-constrained 2D seismic reflection data to characterize the 3D geometry of the Tuatara Volcanic Field located offshore New Zealand's South Island and investigate its relationship with the pre-existing structure. This c. 270 km2 field is dominated by a dome-shaped lava edifice, surrounded and overlain by c. 69 volcanoes and >70 sills emplaced over 40 myr from the Late Cretaceous to Early Eocene (c. 85–45 Ma). The Tuatara Volcanic Field is located above a basement terrane boundary represented by the Livingstone Fault; the recently active Auckland Volcanic Field is similarly located along-strike on North Island. We suggest that the Livingstone Fault controlled the location of the Tuatara Volcanic Field by producing relief at the base of the lithosphere, thereby focussing lithospheric detachment over c. 40 myr, and provided a pathway that facilitated the ascent of magma. We highlight how observations from ancient intraplate volcanic systems may inform our understanding of active intraplate volcanic systems, including the Auckland Volcanic Field.Supplementary material: Interpreted seismic section showing well control on stratigraphic interpretation is available at https://doi.org/10.6084/m9.figshare.c.5004464
40
Park, Jong Myong, Tae Won Kwak, Ji Won Hong, and Young-Hyun You. "Root-Layer Fungi Native to Four Volcanic Topographies on Conserved Ocean Islands: Another Clue to Facilitate Access to Newer Natural Microbial Resources in the Extreme Terrains." Sustainability 15, no. 17 (August 24, 2023): 12824. http://dx.doi.org/10.3390/su151712824.
Abstract:
This study hypothesized that geographic segregation of certain extreme natures of the same kind could be an indicator of access to new natural microbial resources. Root-layer fungi and soil properties native to well-conserved volcanic topographies from two geographically segregated ocean volcanic islands beside the Korean Peninsula were analyzed. Four segregated sampling sites that represented the ocean volcanoes’ unique natural characters (tuff layer, caldera, and two steep cliffs) were examined. A total of 1356 operational taxonomic units classified into 7 phyla and 196 genera were obtained. Soil analysis showed that the sand proportion varied from 32.0–57.4%, and silt, 39.4–64.8%. The tuff layer terrain was the only terrain classified as silt soil. Soil Corg contents ranged from 2.78–15.12%; TN, 0.159–0.843; salinity, 0.001–0.019; and pH, 5.0–7.4. The larger the island area, the less oceanic salinity inflow, but TN and Corg decreased, and pH increased. The Shannon diversity index varied from 4.81–5.23 and was higher at the larger or center of larger islands. As geographic segregation (distance) increased, the proportion of taxa commonly identified decreased. Thus, geographic isolation of certain natural features (e.g., volcanic islands) may be a preferential clue to accessing a broader range of potential microbial resources.
41
Cumberlidge, Neil. "Insular species of Afrotropical freshwater crabs (Crustacea: Decapoda: Brachyura: Potamonautidae and Potamidae) with special reference to Madagascar and the Seychelles." Contributions to Zoology 77, no. 2 (2008): 71–81. http://dx.doi.org/10.1163/18759866-07702003.
Abstract:
The evolutionary relationships between island and mainland faunas of the 24 species of insular freshwater crabs in the Afrotropical region are reviewed in the light of phylogenetic studies. Twenty insular species of freshwater crabs are endemic, and four are also found on the neighboring mainland of Africa. The Atlantic Ocean islands of Sherbro, Bioko, Principe, and São Tomé support five species of Potamonautidae, while the Western Indian Ocean islands of the Seychelles, Zanzibar, Pemba, Mafia, and Madagascar together have 16 species of Potamonautidae, and Socotra has three species of Potamidae. Disjunct distributions of non-endemic insular species of Afrotropical freshwater crabs with conspecifics on the mainland are the result of past lower sea levels that once united islands with the coast. The presence of endemic species of freshwater crabs on oceanic volcanic islands (such as Príncipe and São Tomé) separated from the mainland by deep seas is probably the result of transoceanic dispersal. Endemic genera of freshwater crabs found on oceanic ‘Gondwanan’ islands are derived from ancestral populations on the Eurasian (Socotra) or African (The Seychelles and Madagascar) mainlands that probably reached there by transoceanic dispersal, rather than their being the vicariant descendents of Gondwanan ancestors. Species of freshwater crabs found on islands in the Afrotropical region are either not unique, or are endemic at the species or genus level. The degree of endemism depends on the island’s geological history: whether it is part of the continental shelf, an oceanic island of volcanic origin, or a former part of the ancient continent of Gondwana.
42
Goff, J. "Evidence of a previously unrecorded local tsunami, 13 April 2010, Cook Islands: implications for Pacific Island countries." Natural Hazards and Earth System Sciences 11, no. 5 (May 13, 2011): 1371–79. http://dx.doi.org/10.5194/nhess-11-1371-2011.
Abstract:
Abstract. Tsunami hazard assessments for Pacific Islands Countries (PICs) tend to focus on subduction zone sources. It is generally recognised that while volcanic-related tsunamigenic sources exist, they are probably only of minor relevance to the overall hazardscape of the Pacific. This paper outlines the evidence for a previously unrecorded local tsunami that struck the uninhabited south coast of Mangaia, Cook Islands, on 13 April 2010. The tsunami had a maximum inundation of 100 m inland and a runup of 12 m a.s.l. This event was most probably caused by a small submarine slope failure, the most recent of an unknown number of previous inundations. Since most PICs have a volcanic origin, it is suggested that current perceptions about the local and regional significance of such events is inaccurate. A review of volcanic-related tsunamigenic sources throughout the Pacific reveals a wealth of data concerning submarine slope failures in particular and a more general background of active volcanism. These sources are as relevant to PICs close to or far away from subduction zones. As populations grow and the coastlines of many PICs and those on the edge of the Pacific Ocean become increasing occupied, the likelihood for loss of life from these events increases.
43
Bai, Rui, Ying Shi, and Ying Pan. "Land-Use Classifying and Identification of the Production-Living-Ecological Space of Island Villages—A Case Study of Islands in the Western Sea Area of Guangdong Province." Land 11, no. 5 (May 8, 2022): 705. http://dx.doi.org/10.3390/land11050705.
Abstract:
Accurately identifying the rural production-living-ecological space (PLES) of different islands can help reveal their distinct natural resources and land-use situations, which is significant for the sorted management, subarea utilization, and protection of islands. At present, studies on the PLES of island villages are deficient. For instance, the existing land-use classification system is incomplete; the PLES is poorly identified; and the dominant function of multiple land-use types based on different island geomorphology types is insufficiently investigated. Therefore, a case study was conducted on the island villages of the western sea area of Guangdong Province, based on remote sensing, spatial analysis, and land classification, with field research and the relevant data. In this study, before establishing the PLES system, the islands were classified, including six bedrock islands, 10 sedimentary islands, and one volcanic island. When the PLES system of the island villages was classified, the ecological and utilized areas of the intertidal zone and neritic region should be combined with the island–continent part, and the distinct industrial types should be emphasized, before forming 22 secondary types of PLES. Furthermore, it is found that each island generally has its own dominant space and land-use type. Ecological space (ES) dominates the bedrock islands, and production space (PS) is prominent for sedimentary islands and volcanic islands. Forestland, aquaculture pond, and dryland are the prominent land-use types for bedrock islands, sedimentary islands, and volcanic islands, respectively. The rural residential lands are the main component of living space (LS) in all islands, and the most urban residential lands are distributed on the bedrock islands. The main driving factors for the formation and distribution of island rural PLES are the altitudinal gradient and geomorphic characteristics. The research shows that the main problems of PLES are that the intertidal zones are threatened by aquaculture ponds at various levels, and the development of LS in these islands is generally backward.
44
Dóniz-Páez, Javier, Esther Beltrán-Yanes, Rafael Becerra-Ramírez, Nemesio M. Pérez, Pedro A. Hernández, and William Hernández. "Diversity of Volcanic Geoheritage in the Canary Islands, Spain." Geosciences 10, no. 10 (September 28, 2020): 390. http://dx.doi.org/10.3390/geosciences10100390.
Abstract:
Volcanic areas create spectacular landscapes that contain a great diversity of geoheritage. The study of this geoheritage enables us to inventory, characterise, protect and manage its geodiversity. The Canary Islands are a group of subtropical active volcanic oceanic islands with a great variety of magma types and eruption dynamics that give rise to a wide diversity of volcanic features and processes. The aim of this paper is to identify, for the first time, the diversity of volcanic geoheritage of the Canary Islands and to appraise the protection thereof. To this end, a geomorphological classification is proposed, taking into account the features and processes directly related to volcanism, such as those resulting from erosion and sedimentary processes. The main findings demonstrate that the volcanic geoheritage of the Canary Islands is extremely varied and that this geodiversity is safeguarded by regional, national and, international protection and management frameworks. Even so, and given the enormous pressure of coastal tourism on the coastlines of the islands, we believe that continuing efforts should be made to conserve and manage their volcanic and non-volcanic geoheritage, so that these places can continue to be enjoyed in the form of geotourism.
45
Reyes, Javier, Luis E. Lara, Vanessa Sutherland, Nicolás Aguirre, Carlos Orellana, Folkmar Hauff, and Kaj Hoernle. "Tracing the Origin and Magmatic Evolution of the Rejuvenated Volcanism in Santa Clara Island, Juan Fernández Ridge, SE Pacific." Minerals 14, no. 5 (May 19, 2024): 524. http://dx.doi.org/10.3390/min14050524.
Abstract:
Oceanic intraplate volcanoes sometimes experience late-stage eruptive activity known as rejuvenated volcanism, and contrasting interpretations for its petrogenesis depend on the compositional characteristics. In the Juan Fernández Ridge (JFR), a volcanic chain approximately 800 km in length emplaced on the Nazca Plate, some subaerial occurrences of rejuvenated volcanism have been recognized on the Robinson Crusoe and Santa Clara Islands, both part of the same deeply eroded shield volcano complex. This study aims to understand the origin and magmatic evolution of rejuvenated volcanism on Santa Clara Island, emplaced after ~2.15 Ma of quiescence above the shield sequence, mainly via the analysis of unpublished geochemical and isotopic data. Field reconnaissance identified two nearly coeval rejuvenated sequences on Santa Clara Island: Bahía W (BW) and Morro Spartan (MS), both formed by basanitic and picro-basaltic lava flows with brecciated levels and local intercalations of sedimentary and pyroclastic deposits. In comparison to the chemical signature of the preceding shield-building stage (comprised mainly of basalts and picrites), the two rejuvenated sequences exhibit a notable enrichment in incompatible elements, but the Sr, Nd, and Pb isotopes are very similar to the FOZO mantle endmember, with an apparent additional contribution of HIMU and EM1 components. The geochemistry of lavas revealed the involvement of various processes, including contamination by ultramafic xenoliths, high-pressure fractional crystallization of olivine and clinopyroxene, and potential partial assimilation of oceanic lithospheric components. While the oceanic lithosphere has been considered as a potential source, the isotopic data from Santa Clara lies outside of the mixing curve between depleted mantle (DM, here represented by the North Chile Rise and the East Pacific Rise) and the previous shield stage, suggesting that a lithospheric mantle is not the primary source for the rejuvenated stage volcanism. Therefore, we favor an origin of the rejuvenated volcanism from the mantle plume forming the JFR, supported by similarities in isotopic signatures with the shield stage and high values of 208Pb/204Pb (only comparable to San Félix—San Ambrosio in the vicinity of JFR), implying the presence of a regional source with radiogenic 208Pb/204Pb isotope ratios. In addition, isotopic variations are subparallel to the mixing line between HIMU and EM1 components, whose participation in different proportions might explain the observed trends. In conclusion, we propose that the source of the rejuvenated volcanism on Santa Clara Island is a heterogeneous mantle plume, the same one that fed the shield stage. The rejuvenated volcanism is derived from a secondary melting zone away from the main axis of the plume.
46
Huppert, Kimberly L., J. Taylor Perron, and Leigh H. Royden. "Hotspot swells and the lifespan of volcanic ocean islands." Science Advances 6, no. 1 (January 2020): eaaw6906. http://dx.doi.org/10.1126/sciadv.aaw6906.
Abstract:
Volcanic ocean islands generally form on swells—seafloor that is shallower than expected for its age over areas hundreds to more than a thousand kilometers wide—and ultimately subside to form atolls and guyots (flat-topped seamounts). The mechanisms of island drowning remain enigmatic, however, and the subaerial lifespan of volcanic islands varies widely. We examine swell bathymetry and island drowning at 14 hotspots and find a correspondence between island lifespan and residence time atop swell bathymetry, implying that islands drown as tectonic plate motion transports them past mantle sources of swell uplift. This correspondence argues strongly for dynamic uplift of the lithosphere at ocean hotspots. Our results also explain global variations in island lifespan, which influence island topography, biodiversity, and climate.
47
Faria, B., and J. F. B. D. Fonseca. "Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results." Natural Hazards and Earth System Sciences 14, no. 2 (February 28, 2014): 485–99. http://dx.doi.org/10.5194/nhess-14-485-2014.
Abstract:
Abstract. We describe a new geophysical network deployed in the Cape Verde Archipelago for the assessment and monitoring of volcanic hazards as well as the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression of eruptive activity as widely separated islands have erupted contemporaneously on geological timescales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo Island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions, including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that on Fogo, the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium-frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.
48
Faria, B., and J. F. B. D. Fonseca. "Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results." Natural Hazards and Earth System Sciences Discussions 1, no. 5 (September 25, 2013): 4997–5032. http://dx.doi.org/10.5194/nhessd-1-4997-2013.
Abstract:
Abstract. We describe a new geophysical network deployed in the Cape Verde archipelago for the assessment and monitoring of volcanic hazards, and the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression and widely-separated islands have erupted contemporaneously on geological time scales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that in Fogo the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.
49
Cousin, Jarrad. "Island Colonization: The Origin and Development of Island Communities." Pacific Conservation Biology 15, no. 1 (2009): 75. http://dx.doi.org/10.1071/pc090075.
Abstract:
The theory of island biogeography revolutionized the study of island colonization and extinction. Since its inception in the 1960?s, it has allowed scientists and historians alike to understand reasons for patterns of species distributions on islands, as well as assisting conservation managers to model extinction risk of species populations on isolated islands. Volcanic islands represent a ?tabula rasa?, or clean slate for the study of island biogeography, as invariably, resultant volcanic activity decimates almost all observable life. As such, they form the ideal study unit for examining colonization of islands. The Krakatua eruption of 1883 is such an example, with the resultant blasts scouring the Krakatua islands of almost all life, thus allowing scientists to track the colonisation and successional stages that followed. Another example is Surtsey Island, which emerged from the sea 40 km south of Iceland in 1963. It represented a unique opportunity to examine colonization of a previously non-existent and thus uninhabited island. Given that there are many influences and avenues governing the origin and colonization of life on islands, Island Colonization: The Origin and Development of Island Communities, edited by Tim New, represents an important book compiling information on this topic.
50
Kos'ko, M., and E. Korago. "Review of geology of the New Siberian Islands between the Laptev and the East Siberian Seas, North East Russia." Stephan Mueller Special Publication Series 4 (September 17, 2009): 45–64. http://dx.doi.org/10.5194/smsps-4-45-2009.
Abstract:
Abstract. The New Siberian Islands comprise De Long Islands, Anjou Islands, and Lyakhov Islands. Early Paleozoic, Mesozoic and Cenozoic sediments and igneous rocks are known on the De Long Islands. Cambrian slate, siltstone, mudstone and silicified limestone occur on Bennett Island. Ordovician volcanogenic turbidites, lavas, and small intrusions of andesite-basalt, basalt, dolerite, and porphyritic diorite were mapped on Henrietta Island. The igneous rocks are of calc-alkaline island arc series. The Ordovician age of the sequence was defined radiometrically. Early Paleozoic strata were faulted and folded presumably in the Caledonian time. Early Cretaceous sandstone and mudstone are known on Bennett Island. They are overlain by a 106–124 Ma basalt unit. Cenozoic volcanics are widespread on the De Long Islands. Zhokhov Island is an eroded stratovolcano. The volcanics are mostly of picrite-olivine type and limburgite. Radiometric dating indicates Miocene to Recent ages for Cenozoic volcanism. On the Anjou islands Lower-Middle Paleozoic strata consist of carbonates, siliciclastics, and clay. A Northwest-southeast syn-sedimentary facies zonation has been reconstructed. Upper Paleozoic strata are marine carbonate, clay and siliciclastic facies. Mudstone and clay predominate in the Triassic to Upper Jurassic section. Aptian-Albian coal bearing deposits uconformably overlap lower strata indicating Early Cretaceous tectonism. Upper Cretaceous units are mostly clay and siltstone with brown coal strata resting on Early Cretaceous weathered rhyolite. Cenozoic marine and nonmarine silisiclastics and clay rest upon the older units with a transgressive unconformity including a weathering profile in the older rocks. Manifestations of Paleozoic and Triassic mafic and Cretaceous acidic magmatism are also found on these islands. The pre-Cretaceous structure of the Anjou islands is of a block and fold type Late Cimmerian in age followed by faulting in Cenozoic time. The Lyakhov islands are located at the western end of the Late Cimmerian South Anyui suture. Sequences of variable age, composition, and structural styles are known on the Lyakhov Islands. These include an ancient metamorphic sequence, Late Paleozoic ophiolitic sequence, Late Mesozoic turbidite sequence, Cretaceous granites, and Cenozoic sediments. Fold and thrust imbricate structures have been mapped on southern Bol'shoi Lyakhov Island. North-northwestern vergent thrusts transect the Island and project offshore. Open folds of Jurassic–Early Cretaceous strata are characteristic of Stolbovoi and Malyi Lyakhov islands. Geology of the New Siberian Islands supports the concept of a circum Arctic Phanerozoic fold belt. The belt is comprised of Caledonian, Ellesmerian, Early Cimmerian and Late Cimmerian fold systems, manifested in many places on the mainland and on islands around the Arctic Ocean. Knowledge of the geology of the New Siberian Islands has been used to interpret anomalous gravity and magnetic field maps and Multi Channel Seismic (MCS) lines. Two distinguishing structural stages are universally recognized within the offshore sedimentary cover which correlate with the onshore geology of the New Siberian Islands. Dating of the upper structural stage and constituent seismic units is based on structural and stratigraphic relationships between Late Mesozoic and Cenozoic units in the archipelago. The Laptev Sea–western East Siberian Sea seismostratigraphic model for the upper structural stage has much in common with the seismostratigraphic model in the American Chukchi Sea.