Historical geology is the field of study which seeks to decipher the clues and records bearing on the earth's history. Since the historical geologist cannot observe the history he attempts to interpret (he cannot relive ancient times), scientific methods involving repeatable observation and experimentation cannot be utilized.

by Brian Thomas, M.S., and Jake Hebert, Ph.D. *

In an attempt to learn about past climates, scientists have drilled and extracted cylindrical cores from the Greenland and Antarctic ice sheets. Because of the great thickness of these sheets, the cores can have combined lengths of thousands of meters.