What exactly is magma?

rocky John Githens

Dear John,

Magma is liquid rock INSIDE the Earth. Once this molten material reaches the surface we call it lava. There are places within the Earth (the outermost 200 km) where the temperature (at that pressure) is enough to melt the solid rock in the mantle. The addition of fluids from deeper in the mantle or more minerals help promote melting.

As a student I would melt rocks in a lab. I crushed the rocks into a fine powder, added a solution (to lower the melting temperature of the rock), and put it in an oven (T=1000 C). The graphite or titanium crucible would glow orange. I'd pour my little sample of man-made lava into an acid solution (snap, crackle, pop). The solution was put through a machine that provided chemical data.

Steve Mattox, University of North Dakota 

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