You have now learned that there are different types of soil - sand, loam and clay - and you also learned how the rocks breaks down to form soil.
Recap how soil is formed by rocks breaking down into smaller pieces.
Just like there are different types of soil, there are also different types of rocks.
Rocks differ in the way they were formed and we then classify it as a specific type of rock. Some of the kinds of rock we find on Earth are Sedimentary, Metamorphic and Igneous rock.
We will be learning more about Sedimentary rocks
How it forms
Rocks break up into smaller pieces and eventually form sand. The sand can be blown away by the wind or moved by water and be dropped in another place.
The sand and mud will get stuck together over a long time and will form a new type of rock called Sedimentary rock. We say that this type of rock is made out of sediments - small particles that settle down, usually in water.
Over time more sand and mud is deposited and start forming layers where the sand and mud are put down on top of one another.
Over a long period of time these layers will harden and will form a new rock. The layers can be different colours.
The lower the layer in the rock, the older it is (the layers develop on top of each other, so the oldest layers are at the bottom of the rock).
Sedimentary rock is eroded again by wind and water and broken down into smaller pieces and will turn to sand again.
- Can you remember what is the meaning of the word erosion?
- find a few pictures showing how wind or water have eroded rocks into different shapes.
- look at the picture and explain in your own words how sedimentary rocks form.
There are more than one kind of sedimentary rock
Depending on what type of sediments make up the rock, we will get different types
- Sandstone - this forms when particles of sand get cemented (joined) together
- Shale - this forms out of particles of clay that are cemented together . It is very soft and can be used to write with like chalk.
- Limestone - this forms out of layers of dead sea animals and shells that sunk to the bottom of the sea and get cemented together
- find a picture of each of these different types of sedimentary rock
- you can watch the video for some extra interesting information
Uses of sedimentary rock
Limestone can be cut into blocks and used for building houses or other buildings. It can also be crushed and made into cement and it is used in sculptures, because it can be carved easily.
Limestone is also mixed with the molten sand to make glass stronger and it is even used in cosmetics and medicines.
Sandstone is used in buildings and because it comes in different colours, it is also used for decorative purposes like in a fireplace or pillars in cathedrals. It can also be used as paving stones to make walkways.
- find your own pictures on the different ways in which sandstone are used
Shale can also be used in buildings, especially to make the bricks and can also be used as tiles on a roof or on a floor. Black shale rock is also an important source of oil and gas all over the world.
- Enrichment: Watch the slide show for extra information https://www.slideshare.net/MMoiraWhitehouse/teach-sedimentary-rock-copy
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