The granite rocks that make up Mt. Rushmore crystallized from magma that formed 1.7 billion years ago.
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Courtesy of Peter Nabelek, University of Missouri

Earth's Crust Melts Easier Than Thought
News story originally written on March 18, 2009

In places where continents are slowly smashing into each other and mountains are growing, could it get hot enough in the Earth’s crust for rocks to melt?

A team of scientists looked at this question. They discovered that the rocks of the Earth's crust melt more easily than they thought. They found that as rocks get hotter, they hold onto heat and don’t easily let it go.

We know that rocks melt when continents collide and mountains are built, because there is evidence preserved in the rocks. But scientists wanted to know how this worked. They heated rocks with lasers and measured how long it took heat to conduct through different types of rock.  The scientists noticed that as the heat was increased, the rocks lost some of their ability to conduct. The rocks held onto the heat.

In places where continents are colliding and mountains are forming, the strain of all that moving rock makes heat. This experiment suggests that once the rocks are heated, they stay hot for much longer.

The scientists put their findings into computer models that predict what happens to rocks when they get buried and heat up as mountains form. Hopefully this research will help make the models more accurate.

Last modified April 24, 2009 by Lisa Gardiner.

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