Unit 1: Chapter 7 - Our Changing Planet Flashcards
Structure of The Earth
There are 4 layers to the Earth:
- Crust
- Mantle
- Outer-core
- Inner-core
Crust - 5 - 70km
- We collect our resources from the crust.
Mantle - approximately 3000km deep
- Contains convection currents of semi-magma
Core - Radius of 3500km
- Made of nickel and iron
- Outer core is liquid
- Inner core is solid
The Restless Earth
The Earth once consisted of a a huge land mass called a PANGAEA. The continents are now moving, splitting these continents apart with the CONVECTION CURRENTS in the mantle.
Explaining Convection Currents Within the Earth:
Deep within the Earth, radioactive atoms decay. This releases huge amounts of energy and heats up the molten rocks, causing it expand and rise. Cooler rocks sink and so a convection current is formed.
WEGENER’S REVOLOUTIONARY THEORY:
In the past, scientists thought mountain ranges were created by the crust shrinking in early molten Earth cooling. Then they thought the continents ‘wrinkled’ to produce mountains.
Geologist, Edward Suess thought that a huge southern continent had sunk. This idea was brought forward in the 1900s.
Continental drift was brought forward by Alfred Wegener in 1915, however this was hard to accept because no one knew what CAUSED continental drift.
50 years later his ideas were accepted.
Early Earth’s Atmosphere
Scientists think the Earth was formed 4.5 billion years ago as a ball of molten rock and minerals.
One theory states that there were constant volcanic eruptions that released CO2, NITROGEN AND WATER VAPOUR.
The water vapour then condensed and fell as rain which formed the oceans. The crust of the rock solidified.
As the Earth began to stabilise, the atmosphere was probably mainly CO2. There was also water vapour, methane and ammonia. There was very little oxygen. Nitrogen was also present at the time.
This is atmosphere similar to Mars and Venus.
OXYGEN IN THE ATMOSPHERE
Scientists believe that live on Earth was about 3.4 billion years ago. Bacteria appeared that could break down chemicals as a source of energy.
Later Algae evolved and could do photosynthesis, removing CO2 and making oxygen.
Eventually there was enough oxygen that animals evolved that had to have oxygen to respire.
Microorganisms that were used to low oxygen levels died out as the high oxygen levels killed them.
Life On Earth
Miller-Urey Experiment
The Miller-Urey experiment was an attempt to create amino acids under the conditions of Early Earth Atmosphere. This was an experiment that was conducted in 1952.
They used a mixture of WATER, AMMONIA, METHANE, AND HYDROGEN to model Early Earth Atmosphere. They also used a high voltage to provide enough energy for a reaction, simulating a lightning in a storm. They analysed the mixture and found 11 different amino acids.
The experiment provided enough evidence to suggest it was possible to make life in the Early Atmosphere, however no actual life was made.
OTHER THEORIES
People believe that meteors that crashed on Earth’s surface provided life. This is because in 1969, a meteorite landed in Australia and contained organic life on it.
Gases in the Atmosphere
CARBON ‘LOCKED’ INTO ROCKS.
When animals eat plants, the carbon is transferred too into the bones and teeth. The accumulation of dead bodies leads to the build of carbonate rocks, such as limestone. Some of these rocks are crushed by Earth’s movements to form coal, natural gases and oil, which is ‘locked’ into the Earth’s crust.
CO2 is also dissolved into oceans. It can be reacted with to form insoluble carbonate compounds. These then sink to the sea bed.
AMMONIA AND METHANE
Ammonia and Methane reacted with oxygen.
This led to a build up of water but also some CO2. Nitrogen levels is also build up as it is not very reactive gas.
THE ATMOSPHERE TODAY
200 million years ago, the gases in Earth’s atmosphere stabilised.
78% Nitrogen
21% Oxygen
0.9% Argon
0.04% CO2
Carbon dioxide in the Atmosphere
Over the past 200 million years ago, carbon dioxide levels have not changed much. This is due to carbon cycle between ocean, rocks and the atmosphere.
Plants and oceans are called carbon dioxide ‘sinks’. They absorb excess CO2 when it is produced and released when is it in short supply. Plants remove carbon dioxide from the atmosphere through photosynthesis.
THE CHANGING BALANCE
Due to the release of massive amounts of carbon dioxide through man-made’s fossil fuels, the levels of carbon dioxide is changing.
The sea is absorbing so much carbon dioxide that the reefs are dying because of the very acidic conditions.
