Do you know your rocks?
All rocks are made of minerals: solid materials found in nature. Different rocks have different minerals and form in different ways. Scientists divide rocks into three groups.
Made of layers. Rivers, lakes and the sea deposit (leave) sand, clay and the shells of dead sea animals. Over millions of years the layers are pressed together and become solid rock. That is why we find fossils in them.
Made by volcanoes. Under the surface, melted rock is called magma. When a volcano erupts, it comes out and is called lava. When the lava cools, it becomes igneous rock.
They start as sedimentary or igneous rocks. Deep under the surface, very high heat and pressure (forces pushing on them) change them into new rocks.
Scientists write about what they found: Last week I found a rock. It hadseveral layers, so it was sedimentary. Regular verbs add -ed(look → looked, drop → dropped); some verbs are irregular (find → found, is → was).