Volcano

 

Abstract

History

Different Types of Volcanoes

People of Java

Hazards

Conclusion

Merapi Volcano
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Shield Volcanoes
    Shield Volcanoes are made mostly of fluid lava flows. Flow after flow pours from a central summit vent. It is the calmest of the eruption types, characterized by the effusive emission of highly fluid lavas with low gas contents. It builds up and turns into what looks like a shield. Some of the largest volcanoes in the world are shield volcanoes. The Hawaiian Islands are composed of chains of shield volcanoes. Shield volcanoes are the largest volcanoes on Earth that actually look like volcanoes. Shield volcanoes are almost exclusively basalt, a type of lava that is very fluid when erupted. For this reason these volcanoes are not steep (you can't pile up a fluid that easily runs downhill). Shield volcanoes are the result of high magma supply rates; the lava is hot and little-changed since the time it was generated. Shield volcanoes are the common product of hotspot volcanism but they can also be found along subduction-related volcanic arcs or all by themselves.


Cinder Cone Volcanoes
    Cinder cones are the simplest kind of volcanoes. Cinder cone volcanoes have a bowl shaped crater and barely ever rise over one thousand feet. When cinder cone volcanoes erupt lava blows furiously into the air and breaks up into small pieces called cinders. There are many cinder cone volcanoes in western North America. They form by streaming gases that carry lava blobs and ribbons into the atmosphere to form lava fountains. The lava blobs commonly solidify during flight through the air before landing on the ground. If gas pressure drops, the final stage of building a cinder cone may be a lava flow that breaks through the base of the cone. Cinder cones can occur alone but commonly occur in groups or fields.


Stratovolcanoes
    Some of the world's biggest mountains are stratovolcanoes. Some of the most beautiful mountains are composite volcanoes such as Mount Fuji, Mount Cotopaxi, Mount Shasta, Mount Hood, Mount Rainer and Mount St. Helens.  Most stratovolcanoes have a crater at the top with a central vent or a group of vents where lava comes out. If a lava dome occurs on a steep slope, it may collapse in a dangerous mass of hot rubble. They are constructed from multiple eruptions, sometimes recurring over hundreds of thousands of years, sometimes over a few hundred. They can grow to such heights that their slopes become unstable and susceptible to collapse from the pull of gravity. Most these occur in chains and are separated by several tens of kilometers. There are numerous composite volcano chains on earth, notably around the Pacific rim, known as the "Rim of Fire".