C1 - The Earth Flashcards
What 3 things did Wegener find that made him make his theory?
Identical fossils were found on the opposite sides of the Atlantic Ocean
Africa and South America seemed to fit together like a jigsaw
There were matching layers in the rocks of different continents
Give 3 reasons why Wegener’s theory wasn’t accepted for a long time?
He thought that it was caused by tidal forces and the Earth’s rotation which scientists calculated to be impossible
He had used inaccurate data in his calculations meaning his predictions about how fast the continents were moving apart were very wrong
He had studied astronomy so he wasn’t considered a reliable geologist
Describe the Earth’s structure
The outside is called the crust and is 5 to 50 km thick
The mantle is below the crust and has all the properties of a solid except that it flows very slowly
At the centre, is the core which is made from iron and nickel
Why does the mantle slowly flow?
Within the mantle, radioactive decay takes place which produced a lot of heat causing the mantle to flow in convection currents
What are tectonic plates?
The crust and upper mantle are split into a number of large pieces called tectonic plates
Why do the plates drift and how fast do they do this?
The convection currents in the mantle cause the plates to drift a few centimetres a year
Why do earthquakes happen?
When two plates have built up pressure when trying to move past each other and they suddenly move, a shockwave happens that causes an earthquake
What is the big problem with earthquakes specifically?
We can’t predict when they will happen
How do we predict when volcanoes will erupt?
The molten rock rises up into chambers near the surface before an eruption
Describe phase 1 of the evolution of the atmosphere
The Earth’s surface was originally molten so that any atmosphere just boiled away into space
The surface cooled down a bit and a thin crust formed
Volcanoes gave out lots of gas like carbon dioxide and small amounts of methane, ammonia and water vapour
Ocean formed when the water vapour condensed
Describe phase 2 of the atmosphere’s evolution
Green plants and algae evolved over most of the Earth because they could use the carbon dioxide
The green plants and algae absorbed the carbon dioxide and produced oxygen by photosynthesis
The plants and algae died and very buried under layers of sediment and the carbon and hydrocarbons inside them became locked up in sedimentary rocks as insoluble carbonates and fossil fuels
Describe phase 3 of the atmosphere’s evolution
The oxygen killed off some early organisms but allowed more complex organisms to evolve
The oxygen also created the ozone layer (O^3) which blocked harmful rays from the Sun and enabled even more complex organisms to evolve
Describe the theory of primordial soup
The Earth’s atmosphere contained hydrocarbons, ammonia and other gases billions of years ago
Lightning struck causing a chemical reaction between the gases forming amino acids
The amino acids collected in a body of water out of which life eventually crawled
Who were the scientists that tried to prove the “primordial soup” theory?
Miller and Urey
What did Miller and Urey do to try to prove the theory?
They sealed the gases in their apparatus, heated them and applied an electrical charge for a week
Amino acids were made but not as many as there are on Earth suggesting that the theory is on the right lines
