Some rocks are dramatically changed by forces inside the Earth. Extreme heat or pressure underground can bake, squeeze, or fold rocks into something new. Then they are called metamorphic rocksmetamorphic is Greek for "change of form." (Don't see the metamorphic animation on the left? Click here.)
When sedimentary rocks like mudstone and siltstone are heated to very high temperature, new crystals can grow and may form a completely new rock called schist.
Do metamorphic rocks float? Let's find out!
This piece of schist sinks like a...well, like a stone! So our floating rock must have formed in a different way. Try again!
© The Children's Museum of Indianapolis, 2000