Dating of rocks fossils and geologic events answers

Dating > Dating of rocks fossils and geologic events answers

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Many samples, usually from severaldifferent places, must be studied before assigning a numeric age to a boundary onthe geologic time scale. Multiple dating methods are usually employed so that the dates they suggest can be confirmed with one another.

However the rocks were clearly not laid down slowly over millions of years since there are many tightly folded strata laid down and bent while wet ; there are many polystrate fossils going between rocks allegedly millions of years old; coal contains carbon 14 showing it is not millions of years old. Insects, which evolved from marine arthropods, came onto land during the Devonian 400 Ma , and amphibians i.

THE NUMERIC TIME SCALE - Sedimentary rocks are also usually not dated because they consist of pieces and parts of other rocks cemented together and would not give an age of when the sediment was deposited. The K-Pg extinction is thought to have been caused by the impact of a large extraterrestrial body 10 km to 15 km across , but it is generally agreed that the other four Phanerozoic extinctions had other causes, although their exact nature is not clearly understood.