The origin of the word volcano is Latin and Italian.
How Volcanoes Are Formed
Deep inside Earth, between the molten iron core and the thin crust at the surface, there is a solid body of rock called the mantle. When rock from the mantle melts, moves to the surface through the crust, and releases pent-up gases, volcanoes erupt. Extremely high temperature and pressure cause the rock to melt and become liquid rock or magma. When a large body of magma has formed, it rises thorugh the denser rock layers toward Earth's surface. Magma that has reached the surface is called lava.
Most volcanoes are formed when two plates meet. When they cause a gap in the earths crust, molten lava rises up between the cracks. This kind of volcano is on the oceans floor and is most likely visible. If the amount of lava or magma is large enough, it will create an island. The state of Hawaii was formed by volcanic eruptions. There are at least 8 volcanoes on the islands of Hawaii. However there are many more beneath the oceans surface around Hawaii. The other way a volcano is formed is by two plates coliding and one of the plates going under the other. Only a few volcanoes are formed like this on this planet but they are usually the most violent and dangerous. Sometimes volcanoes are formed in the middle of plates. These are called hotspots. Most volcanoes are found in hotspots.
Cinder Cone Volcanoes
Cinder cone volcanoes, as their name suggests, are formed by ash and and pyroclastic material expelled from a volcanic crater during a very violent eruption. These ejected materials will settle in an area close to the crater and will start piling up until the cone is formed.
Composite Volcanoes
Composite volcanoes or stratovolcanoes are formed by layers of lava, ash, and rock particles. Composite means layers and most are tall and steep with a cone at the top.
Shield Volcanoes
Shield volcanoes are formed from many layers of running lava. It then forms a cone. The main Hawaiian islands are the tops of underwater shield volcanoes.
Lava Domes
A lava dome volcano is a volcano formed by moderately small, bulbous masses of lava which extrude to the surface from within as comparatively cold, viscous lava domes. After extrusion, the lava piles over, cooling the outer surface, then shattering and spilling loose fragments down its sides.
Mount St. Helens, USA—1980
One of the most destructive volcano eruptions in the history of the U.S.
The 1982 eruption of Mount St. Helens caused economic devastation in the region In 1978, volcanologists Dwight Crandell and Donald Mullineaux warned that Mount St. Helens, in Washington State, USA, would erupt before the end of the century. On May 18 1980, their prediction came true with horrifying consequences (Francis).
The disaster began with a large earthquake at 8:32 that morning measuring 5.1 on the Richter scale, and triggering a series of explosions that increased in frequency and intensity. The eruption reached its peak with a violent explosion around 3:50 pm, causing the largest debris avalanche ever recorded to power 14 miles west. On top of this a large cloud of ash rose up to 15 miles into the atmosphere. The combined results of the seismic activity throughout the day devastated the landscape (Brantley).
The environmental cost was one thing, but the human cost was to be even more significant. Moments after the main avalanche, an explosive blast ripped through the area destroying everything in its path, killing 57 people.
But it was the indirect “human cost” which was the main tragedy of Mount St. Helens. Aside from the human lives lost, the eruption caused more than $1 billion worth of damage, primarily to the lumber and agricultural industries. Forests, roads, bridges, recreational sites, houses, trails, railways and wildlife habitats were obliterated or damaged. Tourism to the region fell and unemployment rose in the immediate aftermath of the disaster. The economic consequences for a region which supplies lumber and agricultural resources not only to the Pacific Northwest but also to the whole country were huge (Tilling).
The pic above is very depressing. If signs of depression occur, please call your doctor immediately. What about all da little squirrelies? :'(