Volcanoes

Volcanoes are openings in the Earth's surface through which lava and other materials erupt. Volcanoes are created in two ways;

Subduction Zones	Hot Spots
These zones are areas where one plate subducts (goes under) another plate. Usually it is the thinner oceanic plate that subducts under a thicker continental plate. An extremely hot area created by the melting crust burns a hole in the Earth's crust. Magma leaks through this hole and forms a volcano. The Cascade Mountain Range in Washington State is filled with volcanoes that were formed this way.	Hot spots are areas where the mantle burns a hole in the thin crust of the Earth under the ocean. Magma leaks through this hole forming a volcano. Eventually it forms an island. The Hawaiian Islands are islands formed from volcanoes created by hot spots. These volcanoes begin on the ocean floor.
Image of Subduction Zone	Image of Hot Spot & Hawaiian Islands

There are three kinds of volcanoes:

Cinder	Shield	Composite or StratoVolcanoes
These volcanoes are made up of cinders; tiny pieces of rock. The have a narrow base and steep sides. They are not very tall though. Eruptions are violent and volcanic bombs can be blown out of them.	These volcanoes are made up of hardened lava. They have gentle slopes and begin at the ocean floor from hotspots. Sometimes their eruptions are quiet and sometimes they are violent.	These volcanoes are made up of alternating layers of hardened lava and cinders. They have steep sides and are very tall. Their eruptions are always violent.
Sunset Crater, AZ	Compare the three types of Volcanoes	Stratovolcano

Take a look at any map. You will see mountainous areas all around the eastern, western, and northern Pacific Ocean. These mountains were created by the pushing of the ocean plate against continental crust and subducting creating many volcanoes. A huge concentrations of earthquakes occur here as well. This area is known as the Ring of Fire.

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