Revise GCSE Physics

Question:What three pieces of evidence suggest that craters on Earth were caused by asteroid collisions?

Evidence that craters are created by Asteroid impacts include:

1: The fact that the different types of rocks in the rim and on the surrounding plain appeared to have been deposited in the opposite order from their order in the underlying rock beds.

2: Layers of unusual elements in rocks, such as the layer of Iridium that has been discovered in all the 65 million year old layers of rock all around the globe - suggesting that 65 million years, something put a lot of Iridium metal dust into the Atmosphere to spread around the globe before settling and being buried over time.

3: Unusual elements or minerals found in the bottom of the crater and mixed randomly with the ejected rocks.

Iron on Earth only exists as the iron mineral ores (compounds of iron and other elements mixed up in rocks) The only place pure lumps of iron have been found are meteorites. Before Man learned how to refine iron for iron ore, everything made from iron was made from meteoric iron, which was highly prized.

4. The absence of volcanic activity in the area that could indicate the crater was actually a caldera or caused by impact of eject from a volcano.