Much of evolutionary biology involves the history of organic diversity. Organic diversity has been shaped and affected by the origin and history of planet earth. To appreciate this history we need to acquire some knowledge of the geological processes that have shaped the earth.
History is unique and events are contingent on what has occurred previously.
Much of the contingency of organic evolution is dependent on the unique series of events that shaped the earth, this is why we need to understand some basic geology. A popular hypothesis for the formation of the earth is the nebular hypothesis . This helps to explain the density gradient in the solar system, the closest planets to the sun are terrestrial while those further away are gaseous. Early geologists tried to determine how old the earth was from observations about the features of the earth. Again old, but not old enough.