- In the recorded history of the Earth, about 550 volcanic eruptions have occurred above the surface. However, thousands more take place on the ocean floor. Volcanoes have been around almost as long as the Earth has existed. They are created when the tectonic plates on the Earth's surface either converge or separate, popping up along the fault line in between the two plates. Many cultures view volcanoes as divine creations whose eruptions signify an angry deity.
- Volcanoes inhabit every continent in the world, however not all of these are active. Countries with active volcanoes include Japan, Greece, Mexico, Greenland and Chile. In the United States, potentially active volcanoes exist in Alaska, California, Hawaii, Oregon and Washington. Some of the most famous volcanoes in recorded human history are Mount St. Helens (U.S. state of Washington), Mount Vesuvius (Italy) and Krakatoa (Indonesia).
- Cinder cone volcanoes are the simplest type and they are distinguishable by a high peak and circular opening at the summit. Composite volcanoes are similar, however they are shaped by layers of different kinds of volcanic material. Shield volcanoes are the kind of volcano that is typically associated with the state of Hawaii and are shorter and broader than cinder or composite volcanoes. Although the most common image of a volcano involves a cone-shaped formation that spews lava and poisonous gas, that only typically refers only to the cinder cone volcano.
- All volcanoes feature the presence of magma beneath the surface of the earth in a large chamber. It is not uncommon for a magma chamber to be many miles into the earth. Leading the way from the chamber to the surface is a system of vents and pathways. Once the lava begins to flow, it will ascend out from the volcano and head toward the lowest surrounding points.
- An erupting volcano poses an extremely serious threat to any life form in its lava path. Additionally, poisonous gas is emitted that can kill plants and animals for hundreds of miles. One of the main reasons to study volcanoes is to try to predict when volcanic eruptions are going to occur. With this information, experts can warn those people who will be affected by the danger. However, since volcanoes are very unpredictable, that makes the study of these formations an inexact science. For example, even a volcano that has been declared extinct can suddenly erupt.
