While the fossils of aquatic plants and animals are often preserved at the bottom of lakes and oceans during the natural process of sedimentation, the fossils of terrestrial plants and animals often reflect the occurrence of a natural catastrophe.
Were it not for sudden events that rapidly bury the remains of terrestrial plants and animals, their components would be consumed by predators and scavengers, degraded by natural decomposition and scattered by the forces of wind and water. The best fossils are thus found where catastrophe rapidly entombed the victim, whether dead or alive as that process unfolded. Examples include flash floods, mudslides, avalanches, sandstorms or volcanic eruptions that encased the plants or animals in debris before predation or decomposition occurred. Some of the most complete anatomic preservations were produced when an animal (mammoth, human) was suddenly enveloped in ice or snow, having succumbed to a blizzard or having fallen into a glacial crevasse, frozen in time until a warmer climate revealed their fate.
Such natural catastrophes, spaced throughout geologic time, have offered valuable insight into the evolution of life. Since the timing of the event corresponds to the age of the sediment in which the fossils are found, the sequence of natural history is written in the rock strata of Planet Earth. Of course, tectonic forces may have since moved those sediments from river basins to mountain summits but the story remains intact.
