Volcanoes


 * Volcanic erupotions and magma types**

Deep inside Earth, between the molten iron core and the thin crust at the surface, there is the mantle, a large layer of rock that is largely solid, but flows like plastic. When, for various reasons, rock from the mantle melts, it sometimes moves to the Earth’s surface through weak spots in the crust, releasing heat, gasses, and rock--a volcanic eruption. But why does this solid rock melt and come to the surface?

From Magma to Lava Extremely high temperature and pressure can cause the lower mantle to melt and become liquid rock, or magma. When a body of magma rises through the denser rock layers toward Earth's surface, some of it remains liquid. Magma that has reached the surface is called lava.

Lava Types Magma comes in different "flavors," or compositions. Each of these will produce a different lava, from fluid, fast-moving basalt to slower, more viscous andesite. Because rocks are made up of collections of minerals that melt at different temperatures, the makeup of the rock being melted affects the magma that results.

Exaples of vocanic power

When: A.D. 79 The eruption of Mount Vesuvius buried the towns of Pompeii and Herculaneum under 20 feet of ash and lava, killing an estimated 20,000 people. The ash that buried the town and the people also preserved them. The work of uncovering the ancient cities began in 1748 and continues to this day.