Transcript C1B revision structure of the earth and 706KB

WALT:
The structure of the Earth
WILF:
Identify the structure of the Earth
Describe the evidence that explains how the
Earth is changing
Explain how volcanoes and earthquakes are
formed
atmosphere
The core is a mixture of magnetic metals. The inner core
is solid and the outer core is a liquid
The mantle is a solid but in places behaves like a liquid
The crust is a very thin layer, as thin as 5km in some
places.
The atmosphere is a thin layer of gases about 10km
All the minerals we depend on in our lives come from the
atmosphere, oceans and crust.
The Earths’ crust and the upper part of the mantle are
cracked into huge pieces, known as tectonic plates.
Tectonic plates move very slowly and scientists believe
that the world map was different millions of years ago.
South America was thought to be attached to Africa from
their jigsaw like coastlines.
A scientists called Wegener put forward the idea of
continental drift in 1915. No one believed him at first
then fossils and rocks showing the same species were
found on both continents. Other scientists started to
believe his theory and now continental drift is widely
accepted
• http://www.youtube.com/watch?v=QDqskltCi
xA
Pangaea- Super continent
Tectonic plates move very slowly a few centimetres
every year. This is because deep inside the Earth
radioactive atoms decay releasing huge amounts of
energy. This heats up molten minerals in the
mantle which expand. They become less dense and
rise up. When they cool they sink and are replaced
by warm minerals. Forces created by these
convection current move the tectonic plates.
http://www.youtube.com/watch?v=p0dWF_3PY
h4
At the boundaries of the plates, huge stresses build
up. These forces make the plates buckle and
deform, mountains can be formed in the way.
The plates may also slip past each other. These
sudden movements may cause earthquakes.
• Tectonic plates move a few centimetres every year
because inside the Earth radioactive atoms decay
releasing huge amounts of energy. This causes
convection currents which move the plates
• Stress build up at the boundaries,
• buckled plates = mountains.
• Plates slipping past each other = earthquakes.
For about 200 million years, the proportions of the
different gases in the atmosphere have been much the
same as they are today:
– 80% nitrogen
– 20% oxygen
– Small amounts of
carbon dioxide,
water vapour and noble gases.
During the first 200 billion years there was
intense volcanic activity which released the
gases (carbon dioxide, water vapour and
nitrogen) that formed the early atmosphere and
water vapour which condensed to form the
oceans.
• First billion years - Intense volcanic activity which
released carbon dioxide, water vapour and
nitrogen that formed the early atmosphere. The
water vapour condensed to form the oceans.
• One theory of how the atmosphere began –
atmosphere mainly CO2 with little oxygen (Like
Venus and Mars). There was also small amounts
of water vapour, ammonia and methane
There are many theories about how life began on
Earth.
Scientists think that life began about 3.4 billion
years ago as a simple organism that could make its
own food. This was thought to have evolved into
algae. As the oxygen levels increased the algae
evolved into plants. As more oxygen was available,
animals were able to survive.
The oxygen that plants and algae produced through
photosynthesis is now in our atmosphere.
The atmosphere is explained by the oxygen being
produced from plants during photosynthesis.
But where did the molecules that make up the
cells of even the simplest living things come
from?
The answers are only theories, they are based on
assumptions, the most widely accepted theories
will have the most evidence to support them.
Carbon dioxide is taken up by plants, animals eat plants so it ends being
transferred to animal tissue, bones and teeth.
Over millions of years the dead bodies of the huge numbers of animals
built up in the oceans. Eventually they formed sedimentary carbonate
rocks like limestone (containing mainly calcium carbonate)
Some of these rocks were crushed and formed fossil fuels.
In this way most of the carbon dioxide from the atmosphere ended up
locked up within the Earth’s crust
Carbon dioxide also dissolved in the oceans. It reacted and made
insoluble carbonate compounds. These fell to the seabed and helped
form more carbonate rocks.
• Plants use CO2, animals eat plants. CO2 ends up in
animal tissue, bones and teeth.
• Dead plants and animals form sedimentary carbonate
rocks in the oceans (like limestone)(coal)
• Some of these rocks were crushed and formed fossil
fuels. Fossil fuels are the remains of plants and
animals and are made of hydrogen and carbon
• In this way most of the carbon dioxide from the
atmosphere ended up locked up within the Earth’s
crust
• Over the last 200 million years the levels of carbon
dioxide in the atmosphere have not changed very
much
• This is due to the natural cycle of the carbon in
which carbon moves between the oceans, rocks
and the atmosphere.
• The cycle is self-regulating, so left to itself it the
carbon levels remained balanced.
• The levels only change with human interaction
• The oceans act like a reservoir for carbon dioxide.
They absorb excess it when it is produced and
release it when there is a shortage
• The oceans act as a reservoir for carbon dioxide.
• Increased amounts of carbon dioxide that are
absorbed by the oceans has an impact on the
marine environment. The more CO2 in the oceans
the more acidic the water is. Some plants cannot
cope with acidic water. Photosynthesis removes
CO2 from the atmosphere
• Carbon dioxide levels are being increased by
burning fossil fuels as this releases the carbon
stored within the fossil fuel & respiration
Revision
• Make a mind map on each topic, covering all
the key points
• Work through the chemistry unit in the text
book either making notes or answering the
summary/exam questions. This is your
revision, do what is best for you
• This is your time to ask questions and use the
text.
• Use your time wisely!!!