• Korean Journal of Mineralogy and Petrology
• /
• v.33 no.4
• /
• pp.451-462
• /
• 2020

There are 82 volcanoes active during the 48 weeks of 2019 (January 30 to December 31, 2019; USGS data) Approximately 80~90 volcanoes are active on the Earth for a year. More than 91% of these volcanoes are took place in the circum-Pacific volcanic belt, which is commonly called 'Ring of Fire'. This status coincides with the distribution maps of active volcanoes on the earth: about 80 percent on subduction zone of the convergent plate boundaries; 15 percent on divergent plate boundaries; 5 percent on intra-plate zone. Typically five volcanoes are most active during the survey period (48 weeks); Dukono (Halmahera, Indonesia) 48 times, Aira (Kyushu, Japan) 47 times, Ebeko (Paramushir Island, Russsia) 46 times, Merapi (Central Java, Indonesia) 37 times, Krakatau (Indonesia) 33 times. The comparison of volcanic activity between 2018 and 2019 showed no significant difference. It is assumed that volcanic activity remains stable.

• The Journal of the Petrological Society of Korea
• /
• v.28 no.1
• /
• pp.39-52
• /
• 2019

Volcanic activity, which can read to various danger and hazards to human life, has been part of the Earth's history for a long time. There are approximately 1,520 volcanoes during the Holocene period (about 10,000 years ago) that have been active on Earth. Recently, there are about 210 volcanoes have been recorded since 2010. Meanwhile, there are 83 known active volcanoes in 2018 based on the USGS data. Approximately 80-90 volcanoes are active on Earth for over a year. More than 90% of these volcanoes are located on the circum-Pacific volcanic belt, commonly known as 'Ring of Fire'. This high number of active volcanoes within this area coincides with the distribution maps of active volcanoes on the earth: about 80% on subduction zone of the convergent plate boundaries; 15% on divergent plate boundaries and 5% on intra-plate zone. Five volcanoes are most active during the survey period of 51 weeks: 50 times in Aira (Japan), 49 times in Sabankaya (Peru), 49 times in Sheveluch (Russia), 44 times in Ebeko (Russia) and 40 times in Kirishimayama (Japan). Based on the available data about volcanic activity, there is no significant change in volcanic activity and similar levels of volcanic activity is observed every year.

• 한국해양학회지
• /
• v.25 no.2
• /
• pp.74-83
• /
• 1990

The similarity in Mesozoic geology between the Antarctic Peninsula and South America indicates the possibility that they had situated along the same tectonics line before the separation of southwestern Gondwanaland. The igneous activity around the Antarctic Peninsula, including the South Shetland islands, can be correlated with the South American Cordillera Orogeny due to the subduction of Farallon/Phoenix plate until late Mesozoic. However igneous activity in Tertiary correlates with the tectonics movement accompanying the formations of Drake passage and Scotian sea. The south Shetland islands form a Jurassic-Quaternary miasmatic island arc on the sialic basement of schist and deformed sedimentary rocks. Forming of the South Shetland Islands arc began during the latest Jurassic or earliest Cretaceous from the southwestern part of the archipelago. The igneous activity migrated northeasterly and continued in most areas until late Tertiary. The entire arc-forming period, between late Jurassic and late tertiary times, was characterized by emplacement and eruption of magmas of intermediate between island-arc tholeiite and calc-alkaline types. However, Quaternary volcanic rocks show strong alkaline affinities which corresponds to the switch from compressional to intra: plate tensional tectonics. The rocks of late Cretaceous to Tertiary, mainly found in King George Island, consist of lava of basalt to andesite and intercalated pyroclastic rocks. Some of the volcanic rocks, which ofter called quartz-pyrite lodes'are severely altered and include much content of calcite,silica and pyrite.The stratographic succession of King George Island can be divided into two formation:Fields formation and Hennequin formation.The Fildes formation crops out at the west side of Admiralty Bay n King George Island,while the Hennequin formation at the east side of the bay.These two formtions are thought to be formed contempiranceously.The Fildes formation consists of altered olivine-basalt and basaltic andestie, whereas the Hennequin formation consists of fine-grained hypersthene-augite-andesite.Both formations interclate pyroclastic rocks.

• Ocean and Polar Research
• /
• v.23 no.1
• /
• pp.23-34
• /
• 2001

Geochemical and Sr-Nd isotopic compositions and K-Ar ages are analyzed in volcanic rocks from Weno Island, Caroline Islands. Seven Weno lava samples of alkali basalt and basaltic trachyandesite are aphyric or sparsely phyric comprising olivine, plagioclase, and clinopyroxene phenocrysts. Whole-rock geochemical variation of Weno lavas reflects main fractional crystallization of olivine and Cr-spinel phenocrysts. Newly determined K-Ar ages of Weno lavas range from 6.7 to 11.3 Ma (late Miocene), indicating their formation during primary volcanic stage of Chuuk Islands. Trace element compositions of Weno lavas are very similar to those of typical ocean island basalts (OIBs), suggesting their formation during intra-plate mantle plume activity. The plume composition is isotopically very similar to that of Hawaiian hot spot. However, the age span of Chuuk volcanism is longer than that of the other individual volcanoes in the Pacific.

• Journal of the Korean earth science society
• /
• v.43 no.1
• /
• pp.128-139
• /
• 2022

This study aimed to investigate the tectonic setting of the volcanic edifice at Mt. Baekdu by analyzing petrochemical characteristics of Holocene felsic volcanic rocks distributed in the Baekdusan stratovolcano edifice and summit of the Cheonji caldera rim, as well as Pleistocene mafic rocks of the Gaema lava plateau and Changbaishan shield volcano edifice. During the early eruption phases, mafic eruption materials, with composition ranging from alkali basalt to trachybasalt, or from subalkaline (tholeiitic) basalt to basaltic andesite formed the Gaema lava plateau and Changbaishan shield volcanic edifice, whereas the Baekdusan stratovolcano edifice and Holocene tephra deposits near the summit of the Cheonji caldera comprises trachytic and rhyolitic compositions. Analysis results revealed bimodal compositions with a lack of 54-62 SiO₂, between the felsic and mafic volcanic rocks. This suggested that magmatic processes occurred at the locations of extensional tectonic settings in the crust. Mafic volcanic rocks were plotted in the field of within-plate volcanic zones or between within-plate alkaline and tholeiite zones on the tectonic discrimination diagram, and it was in good agreement with the results of the TAS diagram. Felsic volcanic rocks were plotted in the field of within-plate granite tectonic settings on discrimination diagrams of granitic rocks. None of the results were plotted in the field of arc islands or continental margin arcs. The primitive mantle-normalized spider diagram did not show negative (-) anomalies of Nb and Ti, which are distinctive characteristics of subduction-related volcanic rocks, but exhibited similar patterns of ocean island basalt. Trace element compositions showed no evidence of, magmatic processes related to subduction zones, indicating that the magmatic processes forming the Baekdusan volcanic field occurred in an intraplate environment. The distribution of shallow earthquakes in this region supports the results. The volcanic rocks of the Baekdusan volcanic field are interpreted as the result of intraplate volcanism originating from the upwelling of mantle material during the Cenozoic era.

• The Journal of the Petrological Society of Korea
• /
• v.25 no.4
• /
• pp.409-419
• /
• 2016

The number of volcanoes erupted during the past ten thousand years(Holocene period) on this planet is known to stand around 1,520. Of those volcanoes, the number of active volcanoes during the six-years and seven-month period(January 2010 through the end of July 2016) is totals 209. These findings show that an average of approximate 90 volcanoes erupted every year since 2010. It is also found that over 90 percent of those active volcanoes took place in the circum-Pacific volcanic belt, which is commonly called 'Ring of Fire'. This status coincides with the distribution maps of active volcanoes on the earth: about 80 percent on subduction zone of the convergence of lithospheric plate; 15 percent on spreading zone; 5 percent on intra-plate zone. The period given in this research during 350 weeks, the following three volcanoes showed a frequency of more than 300 times eruption: Kilauea(Hawaii, USA, 338 times), Sheveluch(Kamchatka, Russia, 337 times), and Aira(Kyushu, Japan, 301 times). According to the survey conducted during the given period, there is no conspicuous increase in the frequency of volcano activities. It rather shows that volcanic eruptions took place almost evenly every year.

• Economic and Environmental Geology
• /
• v.36 no.3
• /
• pp.233-242
• /
• 2003

The southeasternmost coastal area of the Korean peninsula has been regarded as a seismologically stable area as neither Quaternary faults nor earthquake activity has been reported. To clarify whether the active tectonic movement has occurred or not, a digital marine terrace mapping and fracture mapping have been done in the coastal area. Bed rocks are composed of the Cretaceous volcanic and sedimentary rocks and the Paleogene granite. Wave-cut platform in the area is smaller and narrower relative to that of the northern coastal area. Most of the platforms in the area have little Quaternary sediment. The platforms except the Holocene terrace (1 st terrace) can be divided into three steps. The lowest platform (2nd terrace) has an altitude of 8-11 m. The broad middle one (3rd terrace) is 17 to 22 m high. The highest terrace (4th terrace) is a narrow and sporadic bench with an altitude of about 44 m high. The lowest terrace is correlated to the 2nd terrace of the northern area, which corresponds to the oxygen isotopic stage 5a. The uplift rate calculated from a graphic method is 0.19 m/ky. This low uplift is typical of an intra-plate, suggesting that the area is tectonically stable. The elevation of the platforms tends slightly lower from the north to the south in the survey area. The decreasing altitude of the platforms towards the south is interpreted to result from a local block tilting during the Latest Pleistocene. This also indicates that the eastern coast of the Korean peninsula has been suffering a subsidence to the south.