Volcanoes

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by briannag82
Last updated 5 years ago

Discipline:
Science
Subject:
Earth Sciences
Grade:
8

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Volcanoes

Volcanoes

Formation of Volcanoes:Volcanoes are formed from past eruptions. Magma that reaches the surface is called lava. Lava flows slowly down the side of the volcano. It then cools and hardens: this new layer of chemicals and minerals become a new layer of sediment on the volcano.

Types of Volcanoes:Cinder cone volcanoes-Cinder cone volcanoes are steep, cone-shaped volcanoes built from lava fragments called 'cinders.' These volcanic cinders, also known as 'scoria,' are glassy volcanic fragments that explode from the volcano and cool quickly. Therefore, they do not fall far from the vent of the volcano, and this builds the steep sides of the cinder cone volcanoes fairly quickly.Shield volcanoes-Shield volcanoes are broad, domed-shaped volcanoes with long, gently sloped sides. If you were to fly over top of a shield volcano, it would resemble a warrior's shield, hence the name. These volcanoes can cover large areas but never grow very tall. The reason these volcanoes tend to flatten out is due to the composition of the lava that flows from them, which is very fluid. This more fluid lava spreads out in all directions but cannot pile up in steep mounds.Composite volcanoes-Composite cone volcanoes, which are also called 'stratovolcanoes' or simply 'composite volcanoes,' are cone-shaped volcanoes composed of layers of lava, ash and rock debris. Composite cone volcanoes are grand sites and can grow to heights of 8,000 feet or more. Mount St. Helens and Mount Rainier, which are both found in Washington State, are impressive examples of composite volcanoes.

Geography:The Ring of FireThe Ring of Fire is a string of volcanoes and sites of seismic activity, or earthquakes, around the edges of the Pacific Ocean. It is the home to 75% of the world's active volcanoes and 90% of great the earthquakes. The map on the right shows the geographic position of the ring of fire.

As shown in this picture, when a volcano erupts, it realeses what is known as volcanic ash and debris. The debris erupts from the volcanoe's vent, launching hundreds of feet in the air and landing to about thousands of feet away. Volcanic debris and ash can be hazardous to nearby homes or villages.


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