A RANDOM WALK
The Geologic Time Scale
In Time: As you drive through the country-side, you may come across an abandoned farmhouse, it windows boarded up, its roof open to the elements, its only inhabitants animals and insects. The surroundings fields, once cultivated, may have been overtaken by the prairie grass that were there long before the farmhouse was built. Within a very short time span, as short as 25 years, that farmhouse may be razed and a subdivision built on the same site. Over a longer time span, the same site may have been at the bottom of a prehistoric ocean, then lifted to a top of a mountain, and finally eroded to the level at which the farm house was built. All things change over time.All things also effect others as they change. In the following pages, I will show you the geologic time scale, a chronological arrangement of geologic time units as currently understood. In addition, I will show you the major steps in evolution that were made possible, in part, by the conditions that existed at every step of that time scale.
