Earth Science

Henry Kitchen
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Earth science AQA GCSE Chemistry

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Henry Kitchen
Created by Henry Kitchen almost 6 years ago
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Earth Science
1 Plate Tectonics
1.1 Alfred Wegener
1.1.1 Alfred Wegener proposed the theory of continental drift at the beginning of the 20th century. His idea was that the Earth's continents were once joined together, but gradually moved apart over millions of years. It offered an explanation of the existence of similar fossils and rocks on continents that are far apart from each other. But it took a long time for the idea to become accepted by other scientists. Before Wegener Before Wegener developed his theory, it was thought that mountains formed because the Earth was cooling down, and in doing so contracted. This was believed to form wrinkles, or mountains, in the Earth's crust. If the idea was correct, however, mountains would be spread evenly over the Earth's surface. We know this is not the case. Wegener suggested that mountains were formed when the edge of a drifting continent collided with another, causing it to crumple and fold. For example, the Himalayas were formed when India came into contact with Asia.
1.1.1.1 Wegener’s evidence for continental drift was that:
1.1.1.1.1 the same types of fossilised animals and plants are found in South America and Africa
1.1.1.1.1.1 the shape of the east coast of South America fits the west coast of Africa, like pieces in a jigsaw puzzle
1.1.1.1.1.1.1 matching rock formations and mountain chains are found in South America and Africa
1.1.2 Alfred Wegener's ideas were not accepted for the following reasons:
1.1.2.1 Alfred was not a qualified Geologist
1.1.2.1.1 People did not want to believe him; it would embarrass them and also make decades of research obsolete.
1.1.2.1.1.1 Also, he had no way of showing how the plates could have plowed through solid rock
1.1.2.1.1.1.1 Another thing was that the theory that Alfred had could be explaied by a theory that includes a large chunk of rock bridging from america to africa which has sunk into the sea.
1.2 An diagram to show plate tectonics
1.3 Tectonic plates
1.3.1 The Earth’s crust, together with the upper region of the mantle, consists of huge slabs of rock called tectonic plates. These fit together rather like the segments on the shell of a tortoise.
1.3.1.1 Although the mantle below the tectonic plates is solid, it does move. This movement is very, very slow – a few centimetres every year. This means that the continents have changed their positions over millions of years.
1.4 The Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates. These are constantly moving at a few centimetres each year. Although this doesn't sound like very much, over millions of years the movement allows whole continents to shift thousands of kilometres apart. This process is called continental drift. The plates move because of convection currents in the Earth's mantle. These are driven by the heat produced by the decay of radioactive elements and heat left over from the formation of the Earth. 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 mountain ranges. It is difficult to predict exactly when an earthquake might happ
2 Earth's atmospheric composition
2.1 Current: Nitrogen 78% oxygen 21% argon 1% carbon dioxide 0.04%
2.2 The early atmosphere was probably mostly carbon dioxide, with little or no oxygen. There were smaller proportions of water vapour, ammonia and methane.
2.3 Why did it change?
2.3.1 The proportion of oxygen went up because of photosynthesis by plants. The proportion of carbon dioxide went down because: It was locked up in sedimentary rocks, such as limestone, and in fossil fuels. It was absorbed by plants for photosynthesis. It dissolved in the oceans. 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.
3 Earth's composition

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