Slides in this set
Formation of sedimentary rocks
Rocks are transported by wind, ice or water. When the water ( for example)
reaches a lake or a sea all the rocks settle to the bottom (deposition), they all
build up forming layers. These layers are called sediments.
The weight of the sediments on top squashes the sediments at the bottom. This
is called compaction. The water is squeezed out from between the pieces of rock
and crystals of different salts form.
The crystals form a sort of glue that sticks or cements the pieces of rock
together. This process is called cementation.
These processes eventually make a type of rock called sedimentary rock. It may
take millions of years for sedimentary rocks to form.
Examples of sedimentary rock are:
Chalk, Limestone, Sandstone and Shale.…read more
Formation of Igneous Rock.
The inside of the Earth is very hot - hot enough to melt rocks. Molten rock forms when
rocks melt. The molten rock is called magma. When the magma cools and solidifies, a type
of rock called igneous rock forms.
Igneous rocks contain randomly arranged interlocking crystals. The size of the crystals
depends on how quickly the molten magma solidified. The more slowly the magma cools,
the bigger the crystals.
If the magma cools quickly, small crystals form in the rock. This can happen if the magma
erupts from a volcano. Basalt is an example of this type of rock. It is called an extrusive
igneous rock because it is formed from eruptions of magma.
If the magma cools slowly, large crystals form in the rock. This can happen if the magma
cools deep underground. Granite is an example of this type of rock. It is an intrusive
igneous rock because it is formed from magma underground.…read more
Formation of Metamorphic Rock
Earth movements can cause rocks to be deeply buried or squeezed. As a result,
the rocks are heated and put under great pressure. They do not melt, but the
minerals that they store are changed chemically, forming metamorphic rock.
When a metamorphic rock is formed under pressure, its crystals become
arranged in layers.
Metamorphic rocks sometimes contain fossils if they were formed from a
sedimentary rock, but the fossils are usually squashed out of shape.
Metamorphic rocks can be formed from any other type of rock - sedimentary
or igneous. These are the two most known metamorphic rocks and where they
· Slate is formed from Shale
· Marble is formed from Limestone…read more
There are three types of weathering :
Chemical: The weathering of rocks by chemicals is called chemical weathering.
Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it.
Minerals in rocks may react with the rainwater, causing the rock to be weathered.
Physical: Physical weathering is caused by physical changes such as changes in
temperature, freezing and thawing, and the effects of wind, rain and waves.
Onion Skin: When a rock gets hot it expands a little, and when a rock gets cold it contracts
a little. If a rock is heated and cooled many times, cracks form and pieces of rock fall away
Freeze Thaw: this is when rain water seeps into faults in rocks. Due to low temperatures it
freezes. The water expands as it turns into ice and cracks the rock. When it melts the rock
Biological: Animals and plants can wear away rocks. This is called biological weathering.
For example, burrowing animals such as rabbits can burrow into a crack in a rock, making it
bigger and splitting the rock. plant roots can grow in cracks. As they grow bigger, the roots
push open the cracks and make them wider and deeper. Eventually pieces of rock may fall
1. How are sedimentary rocks formed?
2. Name an example of a sedimentary rock
3. How are igneous rocks formed?
4. Name the 2 different types of igneous rock and an example for each
5. How are metamorphic rocks formed?
6. Name the two examples and which rock they are formed from.
7. Name the 3 types of weathering.
8. What are the 2 main types of physical weathering.
9. Name the 2 main causes of biological weathering.
10. What does rain water contain to make it contribute to chemical
(All the answers to the above are in the previous slides)…read more