A really useful Revision resource about Geology, covering everything on the topic including:
- Igneous Rocks
-Sedimentary Rocks
- Metamorphic Rocks
-Physical, Biological and Chemical Weathering
- Transportation and Erosion
- Fossils
- Minerals
Using this revision guide you will know everything you need to know about Geology.
2. Igneous rocks are made in a volcano, from
magma (Liquid Rock, which is underground).
There are different types of Igneous Rock. If they
cool outside of a volcano, they will cool quickly.
These are called Extrusive igneous rocks and
you can see small crystals in the rock.
If a rock cools inside a volcano, it will cool slowly.
This is called an Intrusive igneous rock and you
can see large crystals in the rock.
4. The first step is called Sedimentation. This
is where rocks build up a first layer, this
happens by the river transporting them and
leaves rocks on the rive bed.
Sedimentary Rocks are formed by different
layers of rock being squashed together.
This is called compaction.
This process squeezes the water away,
leaving salt crystals that cement the rocks
together. (Cementation)
6. Metamorphic rocks are made far
underground, after the sedimentary rocks
are buried by earth movements. The
rocks are heated up by magma and are put
under lots of pressure.
They don’t melt, but the minerals contained
in the rock are chemically changed,
meaning that they are no longer
sedimentary rocks – but metamorphic
rocks.
7. • Marble – Formed from Limestone
• Slate – Formed from Shale
9. 1. Physical Weathering – There are
multiple types of physical weathering,
one of them is the Freeze-Thaw process.
When there is a crack into a rock,
rainwater flows in. The water freezes in
the cold, and makes the crack wider. The
ice melts. The water gets further into the
crack, making it bigger. This freezing and
then thawing process continues until the
crack gets so big and a large chunk of
rock breaks off.
10. Biological Weathering – Life like
animals and plants can wear away
rocks. This is Biological Weathering. E.g
plants could grow through
cracks, pushing cracks wider, and apart.
Or, animals can burrow into
cracks, making them wider and deeper.
Even people can cause biological
weathering by walking through country
paths. Boots wear away the pathway.
11. Chemical Weathering is where rocks are worn down
chemically. The chemicals are usually from rainwater, which
contains a little acid naturally, where carbon dioxide dissolves
in it. The rocks react to the chemicals are wear away gradually.
Rocks that are Weathered by
chemicals easily:
• Limestone
• Chalk
These rocks are weathered easily
because they are made of a mineral
called calcium carbonate. So, when
acidic rainwater falls, a chemical
reaction happens. New soluble
substances are formed during this
process. These get washed away
and the rock is weathered.
Rocks that are not easily
Weathered by chemicals:
• Granite
• Gabbro
These are hard rocks that weather
slowly.
Although, some of their minerals do
react to the rainwater. New, weaker
substances are formed and they
crumble away.
12. When substances like coal, natural gas, and oil
are burned, sulphur dioxide and carbon dioxide
are released into the air. When the chemicals
dissolve in the clouds, the rainwater becomes
much more acidic than usual. This is known as
‘acid rain’. Acid Rain speeds up the process of
chemical weathering, as the acid is much more
powerful. Acid rain damages statues and
buildings that are made of rock, especially
limestone. Acid rain also kills fish and trees.
13. The rock is weathered somehow. A part of the
rock/cliff would break away. Erosion happens when
the pieces of rock fall off a cliff (Erosion = Is the
movement of the broken pieces away from the
site of weathering.
Then, the rocks can be transported by rivers or
streams. However, slow moving rivers can only
transport small pieces of rock.
When the rocks travel down rivers, they bash
against each other and the river bed and become
much smaller in the process.
14. • Construction
• Medicines
• Fuels
• Sea walls
• Granite – Kitchen worktops
• Pathways
• Limestone bricks
They all depend on rocks and minerals.
15. Fossils are normally only found in Sedimentary rocks. This
happens when an animal or plant died and became trapped
under layers of rock and the skin (if an animal) would
decompose. Only bones would be left and they would be an
imprint in the rock.
If a metamorphic rock was formed from a Sedimentary rock,
there could be fossils, but the fossil would probably be
squashed out of shape.
16. These Minerals must be
supplied by our diet.
Major Minerals
• Calcium
• Chloride
• Magnesium
• Potassium
• Phosphorus
• Sodium
• Sulphur
Major minerals are found in our
body in amounts more than 5
grams.
Trace Minerals
• Chromium
• Copper
• Fluoride
• Iodine
• Iron
• Manganese
• Selenium
• Zinc
Trace Minerals are found in our
body in amounts more than 5
grams.
17. Earth’s rocks
don’t stay the
same forever.
Weathering and
large earth
movements can
change rocks,
and they are
gradually
recycled over
millions of years.
