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Interactives
Volcanoes: Can we predict volcanic eruptions? Melting Rocks
 
Melting Rocks: Try your hand at melting rocks. Before talking about predicting eruptions, we need to look at why they occur.

How do volcanoes form?

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.

Viscosity video clip (Quicktime, 39 seconds, 4,316K)
Take a look at two lava types: pahoehoe and slow, viscous aa.

[Read More About MELTING ROCKS]

 
IntroductionMelting RocksDynamic EarthJudging HazardsForecastingCoping with RiskRelated Resources

"Volcanoes" is inspired by programs from Earth Revealed.

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