A volcano is a geological landform (usually a mountain) where magma (rock of the earth's interior made molten or liquid by high pressure and temperature) erupts through the surface of the planet.
In simple terms a volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth. It is a hole in the Earth from which molten rock (magma) and gas erupt. The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology. As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up “fissures” which are narrow cracks in the earths crust. Once the magma erupts through the earth’s surface it is called lava.
The world's largest, active volcano is Mauna Loa in Hawaii, where famous coffee is grown in the rich volcanic soils. Mauna Loa is 13,677 feet above sea level. From its base below sea level to its summit, Mauna Loa is taller than Mount Everest. Mauna Loa is about 36 m (120 ft) lower than its neighbour, Mauna Kea. However, the biggest volcano explosion we ever had was in Sunda Strait, Indonesia.
Indonesia as a part of the Asia-Pacific’s “Ring of Fire”, has at least 129 active volcanoes. Semeru, Merapi, and Dukono, are listed as number 10, 11, and 12 in “20 World’s Most Active Volcanoes”. Semeru volcano is the highest in Java and has been the site of numerous deaths, the most recent being in August 2000. One of Mount Merapi’s deadliest eruptions was in 1930, when about 1.300 people were killed. A gas cloud
Mount Merapi, Central Java
from the volcano’s 1994 eruption killed 60 people. Both the Semeru and Merapi are in Java.
Krakatoa
Krakatao, is a volcanic island in the Sunda Strait between the islands of Java and Sumatra in Indonesia. It is best known eruption culminated in a series of massive explosions on August 26–27, 1883. It was equivalent to 200 megatons of TNT — about 13,000 times the yield of the Little Boy bomb that devastated Hiroshima, Japan, and four times the yield of the Tsar Bomba, the largest nuclear weapon ever built. The 1883 eruption ejected approximately 21 cubic kilometres (5.0 cu mi) of rock, ash, and pumice, and generated the loudest sound historically reported: the cataclysmic explosion was distinctly heard as far away as Perth in Australia approx. 1,930 miles (3,110 km), and the island of Rodrigues near Mauritius approx. 3,000 miles (5,000 km) distant.
Near Krakatoa, according to official records, 165 villages and towns were destroyed and 132 seriously damaged, at least 36,417 (official toll) people died, and many thousands were injured by the eruption, mostly from the tsunamis that followed the explosion. The eruption destroyed two-thirds of the island of Krakatoa.
The destroyed land has never been repopulated, reverted to jungle, and is now called The Ujung Kulon National Park.
If Volcanoes are that dangerous and terrifying, why were people still live there?
People set up homes on the slopes of volcanoes because of the rich, fertile soil produced. For example, many of the volcanic materials have important industrial and chemical uses. A natural glass that comes from lava is pumice, it is widely used for grinding and polishing metals, stones, and other materials. When lava dries and makes a rock form it is commonly used in building roads. Volcanic ash that has been weathered greatly improves soil fertility.
Volcanic material has a source of precious gems, Opal. It also has a source for metals, gold, silver, molybdenum, copper, zinc, lead, and mercury. When volcanoes erupt, the lava releases some healthy gases, including carbon dioxide and hydrogen. When oxygen mixes with hydrogen, it creates water vapor and that begins the water cycle.
The exhibit says that the most reliable sign of a volcanic eruption is probably earthquakes in the area of the volcano. Other signs can be gas emissions and surface deformation which is kind of like when lots of pressure builds up in the magma chamber in the volcano before the volcano erupts, and it causes cracks on the surface of the volcano. And if there are animals, especially underground animals like moles, running away from their homes, it’s a sign of any disaster.
TOTAL: 715 WORDS.
Source:
http://library.thinkquest.org/TQ0312395/Benefits.htm
http://www.volcanolive.com/active2.html
http://www.woodlands-junior.kent.sch.uk/Homework/mountains/volcanoes.htm
Wikipedia
http://www.volcanolive.com/active2.html
http://www.woodlands-junior.kent.sch.uk/Homework/mountains/volcanoes.htm
Wikipedia
By:
Anggi Ghaisani, Bina, Fritta Aulia, Nadia Dwi, Sheila Claudia
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