Who does not know Mt. Merapi? Almost all over of the world know it, because the volcano's virulence when erupted in 2010 ago. Many world's volcanology experts come to study character changes when this volcano will erupt.
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| Mt. Merapi is touted as the world's most active volcanoes. Since 1548, this mountain has erupted 68 times as much. (Picture from: http://www.republika.co.id/) |
Or with Mt. Tambora on Sumbawa Island? The volcano eruptions in 1815 became the largest eruption in the world of all time. The eruption was heard as far as 2,600 km, and ash fell at least up to 300 km. Darkness visible as far as 600 km from the mountain summit for more than two days. Pyroclastic flows spread at least 20 km from the summit. The Tambora eruption got the scale of seven on Volcanic Explosivity Index (VEI), which means was four times more powerful than the Krakatoa eruption in 1883. An estimated 100 km3 of ppyroclastic trakiandesit out and created caldera measuring 6 to 7 km with depth of 600 to 700 m. Before the eruption, Mt. Tambora height approximately 4,300 m, and after the eruption, the mountain height was left as high as 2,851 m.
Geologists from the Bandung Institute of Technology (Institut Teknologi Bandung / ITB), Budi Brahmantyo, saying that Indonesian volcanoes are known as the "grumpy" volcanoes because of the nature of the activity and the relatively large eruptions. Moreover, Indonesia is included in the Pacific ring of fire.
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| Mt. Krakatoa caused catastrophic explosion in 1883 had global repercussions and left only remnants which continue shown seismic activity until today. (Picture from: http://fajaryusufrock.blogspot.com/) |
"The Indonesian volcanoes are 'fierce' because they have relatively viscous of magma. Especially Indonesia's typical stratovolcano. Means that it is composed of volcanic rock eruption of the type of eruption varies so as to produce a multi-layered arrangement of some rock types. So when they erupting that came out not only the lava material but also the rocks. The outside visual of stratovolcano, the form of mountain is large or giant cone, sometimes has irregular shape because eruption that happen several hundred times," said Budi Brahmantyo.
According to Budi, the type of volcano in Indonesia is different from the volcano in the Hawaiian Islands where the volcano directly contact with the Earth's mantle as a source of lava. Therefore, when they erupted that comes out only the lava, no rocks or pyroclastic because the lava did not have time to freeze. "Almost all Indonesian volcanoes are stratovolcano. Rarely does Indonesian volcano that have type like Hawaiian volcano that directly connected to the Earth's mantle," he adds.
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| A time exposure on September 6, 2010 shows a plume of volcanic ash rising from the crater of Mt. Sinabung as seen from Tanah Karo district in North Sumatra province, some two hours before its eruption. (Picture from: http://www.theepochtimes.com/) |
Meanwhile, based on the level of activity, the Indonesian volcanoes are divided into three types, namely A, B, and C-type. A-type Volcano is a volcano that recorded has erupted at least one times since 1600, and in Indonesia the A-type volcano there are 79. Meanwhile, B-type is the volcano after the year 1600 have not been recorded again has magmatic eruption, but it is still showing volcanic activity symptoms such as solfatara activity. In Indonesia there are 29 volcanoes with this type. And C-type is the volcano has the unknown eruption history, but there are still signs of past events such as solfatara field or fumarola at the weak level. In Indonesia there are 21 volcanoes with this type.
In Java Island itself, the volcanoes that included in A-type are Mt. Gede, Salak, Tangkubanparahu, Papandayan, Galunggung, Guntur, Cereme, Slamet, Butak Petarangan, Dieng, Sundoro, Sumbing, Merapi, Merbabu, Kelud, Arjuno Welirang, Semeru, Bromo, Lamongan, Raung, and Kawah Ijen.
And the B-type volcanoes are Mt. Pulosari, Karang, Patuha, Wayang Windu, Talagabodas, Ungaran, Lawu, Wilis, and Iyang Argapura. And the volcanoes on Java Island that included in C-type, namely Mt. Kiaraberes Gagak, Perbakti, Kawahmanuk, Kawah Kamojang and Kawah Karaha.
"Like Mt. Sinabung, before it included in the classification as B-type volcano because it never recorded erupted since 1600. However, when erupted in 2010, then Sinabung classified as A-type volcano," said Budi explained.
The Volcanoes in the World
Overall, an active volcano in the world amount 500 to 600. The volcanoes are mostly found on the mainland, which is about 83 percent, while the rest are spread as underwater volcanoes or called submarine volcano.
Inside of the ring of fire zone which are shaped like horseshoe and covers an area of 40,000 km2 along from New Zealand, Indonesia, to Chile, in South America, there were 550 active volcanoes.
Approximately 62 percent of the world volcano is located in the Pacific Ocean where 45 percent of the Pacific islands scattered in the West and 17 percent in the suburbs of the North Pacific and the South Pacific. Indonesia itself "contributed" 14 percent of the world's volcanoes to form a line extending along the mountains current 7,000 to 7,500 km and a width of 50 to 200 km, from Aceh in the west end to Halmahera in the east end.
The rest of the other volcanoes in the world that scattered in the island arc and suburban America in the Pacific such as Hawaii and Samoa, and in the islands of the Indian Ocean, the Atlantic such as the Azores, Cape Verde Island, Canada, and Medeira that are the underwater volcanoes, and in the Mediterranean region and Asia Minor in the north and center of the continent, known as the African Rift System.
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| Sicily’s Mount Etna, the current tallest active volcano in Europe, erupted on 2011 that spewing out ash and shooting spectacular bursts of lava high into the air in the process. (Picture from: http://www.inquisitr.com/) |
"For volcanoes are located in subduction on ring of fire zone, the average included in stratovolcano type, which has huge eruption. Including the volcanoes in Japan, which also includes in this type. But Mount Etna that erupted some time ago and Vesuvius's at 1979 in Italy was also included in it, although there are more magma rather than rocks and pyroclastic," said Budi added. *** [EKA | FROM VARIOUS SOURCES | FEBY SYARIFAH | PIKIRAN RAKYAT 14032013]
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