The word "volcano" originally comes from the island of Vulcano in the Mediterranean Sea near Sicily. A long time ago, the people who lived here believed that Vulcano was the chimney of the forge of Vulcan - the blacksmith of the Roman gods. Volcanoes are mountains but are not formed in the same way as regular mountains. A simple explanation of how they are formed is that as magma escapes from under the Earth's crust it hardens and as more and more builds up you eventually have a volcano.

There are three main types of volcanoes: scoria cone, shield volcano, and stratovolcano. Scoria cone volcanoes are the most common and smallest type of volcano. They are usually less than 300 meters high. Sunset crater (pictured below) in Flagstaff, AZ is a classic example of this type of volcano.

Shield volcanoes are very broad and wide. They can range from only a few kilometers to over 1000 kilometers. Mauna Loa in Hawaii (pictured below) is a famous example of this type of volcano.

The stratovolcano is the most obvious type of volcano and the most deadly. Most stratovolcanoes eruptions are highly explosive with deadly pyroclastic flows consisting of hot volcanic fragments and toxic gases. Mt. Fuji in Japan (pictured below) is a famous example of this type of volcano. View a NASA flyby animation of Mt. Fuji.