I have a picture that shows what scientists think parts of North America looked like 300 million yrs ago. ie, trees, plants , insects, rocks. How do scientists know what North America looked like so long ago, if there were no people around to see it?

Question

Count Iblis · Answer

Fossils. By studying fossils and also the geological record one can reconstruct how the Earth looked like.

See also this program about the first trees:

http://www.bbc.co.uk/worldservice/specials/948_discovery_2008/page3.shtml

DrBob222 · Answer

Geologists, paleontologists, hydrologists, and others, study the landscape, the continental plates, fossils, etc and draw conclusions from those studies about various time frames.

drwls · Answer

Fossils and radioactive dating techniques. It is possible to assign an age to layers of earth at different depths.

sasha · Answer

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