1. During the past 4,000 years, Mount St. Helens has erupted more frequently than any other volcano in the Cascade Range. 2. Most of Mount St. Helens is younger than 3,000 years old (younger than the ...

Lava is molten rock from a volcano that reaches the Earth’s surface. Liquid rock below the Earth’s surface is referred to as magma. More than 50% of the world’s active volcanoes above sea level ...

Here’s a look at volcanoes, mountains that open downward to a reservoir of molten rock. More than 80% of the Earth’s surface, both above and below sea level, is of volcanic origin. Lava is molten rock ...