Which Rock Cooled the Fastest?

The difference between an Extrusive and Intrusive igneous rock is the way in which they cool. The inside of the Earth is very hot - hot enough to melt rocks. Lava cools fastest at the earth's surface, while magma, which cools more slowly, can form larger mineral crystals.

Which type of rock cooled very slowly?

Intrusive Igneous Rocks:

Great globs of molten rock rise toward the surface. Some of the magma may feed volcanoes on the Earth's surface, but most remains trapped below, where it cools very slowly over many thousands or millions of years until it solidifies.

Do igneous rocks cool fast or slow?

The magma cools very slowly. As magma cools minerals are formed into an interlocking arrangement producing an igneous rock. As magma cools it undergoes reactions that form minerals. The rate of cooling is very important.