Volcanoes are grouped into four types: cinder cones, composite volcanoes, shield volcanoes and lava volcanoes. Cinder cones are circular or oval cones made up of small fragments of lava from a single ...

At any given time, 20 to 50 of these active volcanoes are erupting. The proximity of people and buildings makes it important to study volcanoes and understand the hazards. The center of the Earth is ...

(CNN) — Here's some background information about volcanoes, mountains that open downward to a reservoir of molten rock. Facts: More than 80% of the Earth's surface, both above and below sea level, is ...

Volcanoes can look like small mountains or hills. A volcano is an opening in the Earth's crust that allows magma, hot ash and gases to escape. Composite volcanoes are the most common type of volcano.