Rocks provide evidence for changes in the Earth:
- Erosion – the Earth’s surface is made up of LAYERS of rock, one on top of the other with the oldest at the bottom. The layers are made of compacted SEDIMENT, which is produced by weathering and EROSION. Erosion changes the surface of the planet over long periods of time.
- Fossils – plants and animals trapped in layers of sedimentary rock have formed FOSSILS, providing evidence of how life on Earth has changed over millions of years.
- Folding – some rocks look as if they have been FOLDED like plasticine. This would require a big force to be applied over a long period of time – further evidence that the Earth is very old.
- Mountain formation – if MOUNTAINS were not being formed, the whole Earth would have been worn down to sea level by erosion.
Rock processes
Rock processes seen today can account for past changes.
When it comes to I/GCSE Physics, scientists estimate that the Earth is around 4500 million years old – it has to be older than its oldest rocks - and when it was first formed it was completely molten (hot liquid) and would have taken a very long time to cool down. The oldest rocks that have been found on Earth are about 4500 million years old.
The age of the Earth must be greater than the age of it oldest rocks.
Alfred Wegner
Alfred Wegner (1880-1930) was a meteorologist who put forward a theory called CONTINENTAL DRIFT. He saw that the continents fitted together like a jigsaw, with the MOUNTAIN RANGES and SEDIMENTARY ROCK patterns matching up almost perfectly. There were also FOSSILS of the same land animals on different continents. Wegner proposed that the different continents were once joined together but had become separated and drifted apart.
Refer toI/GCSE Physics,Wegner also claimed that when two continents collided, they forced each other upwards to MAKE MOUNTAINS.
Evidence For | Evidence Against |
● The same types of fossilised animals and plants are found in South America and Africa ● The shape of the east coast of South America fits the west coast of Africa, like pieces in a jigsaw puzzle ● Matching rock formations and mountain chains are found in South American and Africa ● Closely matching coastline | ● He was not a geologist and was therefore was considered as an outsider ● It was a big idea but he was not able to provide much evidence ● The evidence could be explained more simply by a land bridge connecting the continents that has now sunk or been eroded ● The movement of the continents was not detectable. |
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