The
Earth is our source of raw materials Chemical reactions occur at different
rates.
We get:
– rocks, minerals and fossil fuels from the Earth’s
crust;
– water, salt and other minerals from the
seas;
– important gases from the
air;
– foods, fibres and timber from living
things.
Rocks
are mixtures of different minerals.
Minerals are single substances with a
chemical name and a formula e.g. pure sand is silicon dioxide,
2.
Layers
of the Earth The Earth has four layers. The temperature
and density of these layers increase from the atmosphere to
the core.
3.
Weathering Weathering is the breaking up of rocks.
There are two kinds of weathering.
Physical weathering
– by the expansion and contraction of rocks as the
temperature changes;
– by the freezing of water in cracks.
Chemical weathering
– by the action of water on feldspar in granite;
– by the action of rainwater on carbonates such as
limestone.
4.
Rock types There are three different types of
rock.
5.
Plate tectonics
The Earth’s crust is cracked and
broken into vast sections called plates.
These plates float on the dense liquid mantle. The continents
form the visible parts of the plates above the oceans.
The plates move very, very slowly due
to convection currents in the liquid mantle. The study of
the movement and interaction of the giant plates is called
plate tectonics.
– When plates slide past each other,
tear faults and earthquakes can occur.
– When plates move apart, normal
faults, rift valleys and volcanoes can occur.
– When plates push against each other,
reverse faults and folds can occur.
