A long time ago the Romans called the mountain "Vulcano". They named it that because "Vulcan" was the ancient Roman name for god of fire. Volcanoes are openings in the earth where lava, hot gases, and rock fragments blow out of the opening. Such openings occur when melted rocks from deep inside the earth bursts through the earth's crust. Most volcanoes are mountains, especially cone shaped ones, which grow around the opening by lava and other things blown out during an eruption.   A volcanic eruption is a spectacular sight. Some eruptions have huge clouds rise over the mountain and rivers of lava flowing down its sides. The kind of eruption most common in Hawaii has red hot ash and cinders shooting out of the mountain top. The volcano begins as magma (melted rocksinside the earth) partly melts the other rocks around it. When the rock melts it makes a big amount of gases which becomes mixed with the magma. The gas-filled magma rises toward the earth's surface and melts the rocks that surround it, forming a holding area. This is called a magma chamber and is the substance that causes volcanic eruptions.   When the magma and the reserve is under great pressure from the solid rocks around it, the pressure causes the magma to blow a conduit or channel in the weak part of the rock. The magma moves to the surface through these conduits. When the magma reaches the surface, gases are released. The gases and magma blow an opening called a central vent. Most magma and other things blast through these vents. The material gradually blows up around the vent, forcing a volcanic mountain. After the eruption stops, a bowl-like crater usually forms at the top of the mountain and the vent lies at the bottom of the crater. Kinds of Volcanoes Volcanologists, people who study volcanoes, have put them into three groups. One is called the shield volcano. These are the volcanoes you see in Hawaii. They are shaped in wide sloping mounds. These volcanoes rarely erupt fiercely, but the lava that comes out forces people to leave their homes. Dome volcanoes are highly dangerous. These volcanoes are very thick so lava cannot spread. Cinder cones are explosive. Their cones are made of mostly ash.

 

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