Kathleen McCullough, age 9, of Los Angeles, California, for her question;

What is metamorphic rock?

Geologists, who are the rock experts, divide all the different rocks into three main classes. There are igneous rocks, sedimentary rocks and metamorphic rocks. At some time in their history, the igneous or fireformed rocks were hot enough to melt. The sedimentary rocks are the dregs rocks. At some time they have been chomped to powder and gone through a soupy stage of muddy water. The metamorphic rocks are igneous or sedimentary rocks which have been through still another trying experience.

Their class name, metamorphic, means changed. These rocks have been changed by heat, pressure or both. This could happen to rocks buried deep under heavy layers or from movements of the earth’s crust, It could also happen to the rocks close to seething lava or magma, which is buried lava, Usually, only the texture of the rocks is changed.

In severe cases, the very minerals of the rocks are changed. Garnet, marble, slate and quartzite are some of the metamorphic rocks. Under heat and pressures soft limestone is refined and hardened into marble and shale ::comes slate. Course grained sandstone becomes fine grained quartzite.