1.1 The Earth’s crust, its atmosphere and oceans are the only
sources of the resources that humans need.
1.1.1 The Earth has a layered structure, including the core (made from
liquid nickel and iron), mantle (has the properties of a solid, but
can flow very slowly - magma) and crust (relatively thin and rocky).
18.104.22.168 The radius of the core is just over half the
radius of the Earth. The core itself consists
of a solid inner core and a liquid outer core.
The crust and upper mantle are cracked into
large pieces called tectonic plates. These
plates move slowly, but can cause
earthquakes and volcanoes where they meet.
22.214.171.124.1 The plates are constantly
moving due to convection
currents in the magma, which
are driven by the heat
produced by the natural decay
of radioactive elements in the
Earth. This process is called
126.96.36.199.1.1 Where tectonic plates meet, the
Earth's crust becomes unstable
as the plates push against each
other, or ride under or over each
other. Earthquakes and volcanic
eruptions happen at the
boundaries between plates, and
the crust may ‘crumple’ to form
188.8.131.52.1.1.1 It is difficult to predict exactly when an earthquake or
volcanic eruption might happen because we cannot
observe this phenomenon. We simply don't have the
equipment to measure the stresses on the rocks
bordering the faults, to see the underlying movement of
the more plastic rocks of the mantle that lie 50-160 km
below the surface, and to know how much longer the
rocks can withstand the strain before they crumble
under the pressure.
184.108.40.206.220.127.116.11 The theory of plate tectonics and continental
drift was proposed by Alfred Wegener.
Wegener’s theory suggested that mountains
were formed when the edge of a drifting
continent collided with another, causing it to
crumple and fold. It took more than 50 years
for his theory to be accepted because it was
difficult to work out how whole continents
could move: it was not until the 1960s that
enough evidence was discovered to support
the theory fully.
2 C1.7.2 The Earth's Atmosphere
2.1 Air is a mixture of gases with different boiling points
and can be fractionally distilled to provide a source of
raw materials used in a variety of industrial processes.
2.1.1 For 200 million years, the proportions of different
gases in the atmosphere have been much the
same as they are today: 80% nitrogen, 20%
oxygen and small proportions of various other
gases, including carbon dioxide, water vapour
and noble gases.
18.104.22.168 During the first billion years of the Earth's
existence there was intense volcanic
activity which released the gases that
formed the early atmosphere and water
vapour that condensed to form the oceans.
22.214.171.124.1 There are several theories about how the
atmosphere was formed, which was
probably mostly carbon dioxide with little or
no oxygen. There were smaller proportions
of water vapour, ammonia and methane. It
is thought that the atmospheres of Mars
and Venus today are similar to the early
atmosphere of the Earth.
126.96.36.199.1.1 There is evidence that the first living things appeared on Earth billions of years
ago. There are many scientific theories to explain how life began. One theory
involves the interaction between hydrocarbons, ammonia and lightning.
188.8.131.52.1.1.1 Stanley Miller and Harold Urey carried out experiments see if substances now made by living things
could be formed in the conditions thought to have existed on the early Earth. They sealed a mixture
of water, ammonia, methane and hydrogen in a sterile flask, which was heated to produce water
vapour. Electric sparks were passed through the mixture of water vapour and gases, simulating
lightning. After a week, contents were analysed. Amino acids, the building blocks for proteins, were
found. The Miller-Urey experiment supported the theory of a ‘primordial soup’, the idea that complex
chemicals needed for living things to develop could be produced naturally on the early Earth.
184.108.40.206.220.127.116.11 Plants and algae photosynthesised; increasing oxygen
and decreasing carbon dioxide in the atmosphere.
18.104.22.168.22.214.171.124.1 The decrease of carbon dioxide in
the atmosphere was not just because
of photosynthesis; most of the
carbon gradually became locked up
in sedimentary rocks as carbonates
and fossil fuels and carbon dioxide
dissolved in the oceans.
126.96.36.199.188.8.131.52.1.1 Limestone was formed from the
shells and skeletons of marine
organisms. Fossil fuels contain
carbon and hydrocarbons.
184.108.40.206.220.127.116.11.1.1.1 The oceans act as a reservoir
for carbon dioxide but
increased amounts absorbed
by the oceans is making it
more acidic and has an impact
on the marine environment;
making the shells of sea
creatures thinner than normal.
18.104.22.168.22.214.171.124.126.96.36.199 Today, the burning of fossil fuels is adding carbon dioxide to the atmosphere
faster than it can be removed. This means that the level of carbon dioxide in the
atmosphere is increasing, contributing to global warming.