Rocks are found naturally in the ground.

They have many different properties which give them a variety of uses

Rocks we will be investigating

Slate

Slate is a hard and waterproof.
It splits easily into thin sheets which is why it is good for putting on roofs


Marble

Marble has an attractive colour and can be easily cut and polished.  Because of this, it is often used in buildings.


Chalk


Chalk wears away very easily which is why it ideal for making sticks of chalk to write on blackboards!

Chalk is made from the fossilized remains of tiny sea animals.
Whenever you see a chalk hill you know that it used to be under the sea millions of years earlier.


Granite

Granite is very hard. It is often used to make steps and roads as it is a rock that doesn’t wear away easily.


Limestone

Limestone Is also quite soft and can be easily carved or shaped. It is often used as a building material but is easily eroded by the rain.


Pumice

Pumice is formed when volcanos erupt. The little holes happen because bubbles of gas get trapped in the rock as it cools.


Some properties of rocks

Hardness, permeability, ease of splitting, weight

Hardness:
A hard rock will always be able to scratch a softer rock but not the other way around.
eg granite will be able to scratch slate but slate cannot scratch granite

Hard rocks eg Granite
Good for building roads or steps.
Soft rocks eg limestone
good as a building material because it is easy the shape

Permeability:
Permeability means how waterproof a rock is.
Chalk is permeable, which means water will soak into it.

Slate is impermeable which means  water will NOT soak into it.
Slate is used on roofs.
(slate is also easy to split)

Weight:
Pumice is a very light rock
It is often ground up and used to make light-weight concrete of blocks.


Fossils

Fossils are the remains of animals that died a long time ago.
The process by which a fossil is formed is called ‘fossilisation’.

Fossils can tell us about living things in the past and how the environment has changed over time.

Fossils are easy to find if you know where to look for them.

The photo above shows some shell-fish called ammonites.
Ammonites lived in the seas between 240 – 65 million years ago.

When they died their shells would fall into the mud at the bottom of the sea.
Over time the mud turned into rock trapping their shells.

Older fossils will be trapped at a greater depth than newer fossils.


Soils:

  • Soils are a mixture of tiny particles of rock, dead plants and animals, air and water.
  • The best soil (called loam) is a mixture of sand, clay and humus.
    It is dark in colour and crumbly in texture
  • Good soil often contains millions of tiny animals.

 

Sandy soil: often very dry as water drains away quickly

Clay soil: Easily gets water-logged as it doesn’t drain

Humus: the name given to the dead plants found in soil
Humus provides food for the plants and helps keep the soil moist

Peat: has no rock particles at all. It is just rotting roots and leaves.