What are the three types of rocks? - BBC Bitesize (2024)

Many landscape features are made of rock but not all rock is the same. There are three types of rock: sedimentary, igneous and metamorphic.

In this article you can learn:

• How different types of rock are formed
• What causes ripple marks in sedimentary rocks
• How tectonic plates can move rocks

This resource is suitable for Landscapes topics for primary school learners.

There are three main types of rock:

Sedimentary rocks are made up of tiny broken pieces of rocks, crystals or .

• Rock breaks and is into tiny pieces and moved by wind, ice or water.
• The bits of rock are somewhere new.
• Deposits build up in layers called sediments.
• The layers of sediment become crushed and compacted until they harden to form sedimentary rock. It can take millions of years for sedimentary rocks to form!
• For example, limestone is a sedimentary rock made of calcium carbonate. Learn more about limestone here: Limestone landscape

Here are some examples of sedimentary rocks:

• Ripple marks form when wind or water moves loose sediment, like sand. The wind or water creates grooves in the sediment.
• Ripple marks can often be spotted on beaches when waves come up onto the shore and move the sand.
• Over time, these marks can fossilise, which means the ripple marks have been preserved. This happens when layers of sediment have become compacted and formed sedimentary rock, like sandstone, but the ripple marks have been left behind.

• Igneous rocks are formed from or .
• Rock from the Earth's crust and mantle becomes molten because of changes in heat and pressure.
• Some of this molten magma rises up through the Earth's crust.
• The magma cools down as it rises. Some of it underground. Some of it rises to the surface as lava before it solidifies.
• Learn more about igneous rock formations here: Igneous landscape

Here are some examples of igneous rocks:

A metamorphic rock starts out as one type of rock but changes into another. For example, a metamorphic rock can be formed because of high heat or high pressure.

Here are some examples of metamorphic rocks:

Different rocks can be transformed into metamorphic rocks when push into each other. The older rocks of one tectonic plate are forced up and over the younger rocks of the other plate.

This is how Lewisian Gneiss was formed. The Lewisian Complex is found in the north west of Scotland and contains some of the oldest rocks in the world! Some of this rock is more than three billion years old.

Learn more about tectonic plates here: Tectonic movement

• geopark - An area that is recognised because of its geological importance. Geology is the scientific study of rocks and stones.
• sedimentary rock - A soft rock made up of tiny broken pieces of rocks and crystals.
• sandstone - A type of sedimentary rock.
• deposition - When sediments, soil and rocks are moved by wind, ice, water or gravity and left behind.
• sediment - Materials such as stones and sand that is moved from once and deposited in another.
• ripple mark - Wavy marks or ridges left on sand, mud or rock by the movement of water or wind.
• metamorphic rock - A rock that started out as another type of rock but has been changed. For example, a metamorphic rock might be formed because of high heat or high pressure.
• tectonic plates - Large slabs that fit together to make up the Earth's crust.
• magma - Molten rock that is so hot it has turned into liquid. When magma reaches the surface of the Earth it is called lava.
• mantle - The layer beneath the Earth's crust. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.
• igneous rock - Rock that was made from magma.
• igneous intrusion - A type of rock feature that forms when magma (molten rock) cools below the surface of the Earth.

Make a poster about a rock type.

Choose from sedimentary, igneous and metamorphic rocks and design a poster all about this rock type.

Ideas to think about for your poster:

• How is the rock formed?
• What are some examples of this type of rock?
• Where might you find this type of rock?

If you need some help designing your poster, take a look at this guide: How to make a poster