There are three main kinds of rock. Igneous rock, such as granite, forms when melted rock cools and goes hard. Sedimentary rock, such as sandstone and chalk, forms when layers of sand, mud and shells are pressed together over a very long time. Metamorphic rock, such as marble, forms when other rock is changed by great heat and pressure underground.
Soil is made of tiny bits of broken rock mixed with rotted plants and animals, air and water. Fossils are the remains or traces of living things from long ago, kept in rock. Most fossils form in sedimentary rock when a dead plant or animal is quickly covered in mud. Layers of rock are like pages of history: lower layers are usually older.
Worked example
A rock has layers and a fossil shell in it. What kind of rock is it most likely to be?
- Layers form when sediment builds up.
- Fossils form when living things are buried in sediment.
Answer:So it is most likely sedimentary rock.
Key words
- igneous
- rock made when melted rock cools
- sedimentary
- rock made from layers pressed together
- metamorphic
- rock changed by heat and pressure
- fossil
- the remains of an ancient living thing in rock
New questions every time.
NGSS-referenced: 4-ESS1-1