 Comparing fossils with similar life forms alive today make it possible to infer facts about Earth’s past environments.  Ex. most present-day corals live in shallow, warm ocean waters, so we can assume that coral fossils formed in an environment that was the same  The movements of the plates and their associated landmasses have changed the Earth’s environment over time

 Environmental Evolution and Rock Types: As Earth’s environments changed over time, specific rocks and minerals formed, as well as deposits of fossil fuels. (ex. worldwide coal deposits of today were formed from swamps formed during the hot and humid conditions of the Carboniferous Period)  Deposits of salt and gypsum are found in western NYS because old oceans that covered the state evaporated during the hot and dry Silurian Period (noted on reference tables)

 Most organisms decompose or are eaten after they die, so only a small percent leave fossils  Fossils found in Africa suggest that we have evolved over the past 4 million years from apelike animals  This is only about 1/10 of 1% of Earth’s age  Humans are a very recent life-form

 Mass Extinction: Points in geologic time where a large number of species become extinct  Although not certain, scientists link many of these mass extinctions to asteroid, comet or meteoroid impact events  It is believed that an object from outer space that left a crater in southern Mexico wiped out the dinosaurs and many other species about 65 million years ago

 Extinction was more likely a result of global climatic change that resulted from the debris thrown into the air by the impact, rather than the impact itself  The debris would have stopped sunlight from reaching Earth’s surface.  This would have disrupted the whole food chain