2. Volcanologists study and classify volcanoes according to their activity. They use special instruments that can determine if pressure in a volcano is building up. They check to see if the top of a volcano is plugged with cool lava. Since volcanologists are able to predict volcanoes, people usually have time to evacuate before an eruption.

3. A volcano is… when hot lava breaks through a weak spot in the crust. As magma shoots out the crust, the cooling magma called lava becomes hard. After a while, this hard lava forms a volcanic mountain.

4. Volcanic eruptions occur only in certain places and do not occur randomly. That's because the Earth's outermost shell -- the lithosphere -- is broken into a series of slabs known as lithospheric or tectonic plates. These plates are rigid, but they float on the hotter, softer layer in the Earth's mantle. There are 16 major plates. As the plates move about, they spread apart, collide, or slide past each other. Volcanoes occur most frequently at plate boundaries.

5. There are different types of volcanoes. The differences are the way they are made, the type of lava they contain and the kind of volcanic activity they produce. The most common types of volcanoes are: 1. Shield Volcanoes 2. Dome Volcanoes 3. Cinder Cone Volcanoes

6. Found in Hawaii Wide shaped, sloping mounds Liquid lava flows from the crater and the sides of the volcano Flow after flow of lava pours out in all directions from the central vent, building a broad, gently sloping cone Belknap Shield Volcano, Oregon

7.  Cones are formed from cinders, which are small, jagged pieces of rock and ash. When a cinder cone volcano erupts, these small cinders are scattered all over.  Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world.  Volcanoes have a bowl-shaped crater and rarely rise more than a thousand feet or so above their surroundings.

8.  DOME SHAPED VOLCANOES ARE THE MOST DANGEROUS!  Volcanic domes are mounds that form when viscous lava is erupted slowly and piles up over the vent, rather than moving away as a lava flow.lava flow  Most domes are composed of silica-rich lava which may contain enough pressurized gas to cause explosions during dome extrusion.  The sides of most domes are very steep.

9. There are three different classifications of volcanic activity: Active Dormant Extinct

10. An active volcano is one that has erupted recently or vocanologists see the possibility of an eruption soon. Active volcanoes are watched very closely so that people and animals in the area can be moved to a safe place.

11.  Dormant (sleeping) volcanoes are ones that have been sleeping for a long time, but still have signs that it may erupt.  A volcano becomes dormant when the vent is blocked by hardened lava, called a plug, or if the magma seeps back under the earth’s crust.  Volcanoes can be dormant for hundreds of years. Then suddenly a volcano will erupt again. The eruption is usually very violent. The plug stops the magma from rising. Then pressure builds up, the plug gives away and a large eruption is caused.

12. An extinct volcano is one that has not erupted for years. Sometimes it is hard to tell if a volcano is dormant or extinct. They will be listed as dormant until volcanologists are sure there will be no more eruptions.