The oldest fossils (of bacteria) are 3.8 billion years old.ocks at different locations on Earth give different "snapshots" of the geologic time column.
Fleeting trails of light are called meteors or shooting stars and they are created by small particles, some no bigger than a grain of rice, as they are completely burned up high in the atmosphere: about 100 km (or 60 miles) above the Earth. Space debris is collectively termed meteoroids, those larger fragments that reach the ground are called meteorites. If one collides with Earth it would cause a major catastrophe. It is now generally accepted that the dinosaurs were pushed into extinction by a collision between a large chunk of space rock and the Earth: the evidence for this collision is provided by the large 180 km diameter impact crater near the town of Chicxulub on the Yucatan Peninsula, Mexico. It is a certainty that another collision will occur at some time in the future.
In some ways, it is a natural record of the Earth's history.
To understand stratigraphy and relative dating, four basic principles must be mastered.
At a particular location, the rocks never fully represent the entire geologic rock column due to extensive erosion or periods of non-deposition or erosion.
For example, rocks named Juras (for the Juras Mountains) in France and Switzerland were traced northward and found to overlie a group of rocks in Germany named Trias.