Over time, the layers are compressed and glued together.Metamorphic rocks are formed from other rocks, igneous or sedimentary, which are heated and compressed underground.Igneous rocks are formed ...

Laid down over millions of years, these rock layers contain a permanent record of the Earth's past, including the fossilized remains of plants and animals buried when the sediments were formed.

The beginnings of a strange layer of molten rock deep inside the Earth may have ... Exactly how this layer formed has ...

The next layer is the mantle. Many people think of this as lava, but it's actually rock. The rock is so hot ... to build mountains or rifting apart to form new seafloor. Continents are composed ...