The Earth routinely experiences cycles of warming and cooling. Although scientists still are trying to figure out exactly what drives these cycles, they believe they are caused mostly by changes in our planet's orbit around the sun, the composition of our atmosphere and ocean currents. An extreme period of cooling is called an "ice age," and is partially defined by the growth of huge glaciers covering the Earth. The last ice age ended approximately 12,000 years ago.
How long has civilization affected environment?
Answered by Ellen Stockstill and Discovery Channel
How much carbon dioxide do people produce each year?
Answered by Science Channel
How do traditional burial materials impact the environment?
Answered by Planet Green