Geological Time Scale
The information about the earth’s history came from many fossils,
relative-dating methods, and absolute dating methods from the
entire planet. Scientist created an arrangement of rock layers based
on age, with the oldest on the bottom and the youngest on the top.
The layers are distinguished from each other by specific fossils and
the type of rock. This is called a geologic column.
Scientists have divided the earth’s history into smaller units.
Era – This is the largest unit in which there are four: Precambrian,
Paleozoic, Mesozoic, and Cenozoic. They are divided by a major
geological or biological occurrence
Periods – These are sub-units of an era and are usually
characterized by a specific fossil or group of fossils.
Epoch – These are sub-units of a period and are only used in the
Cenozoic era due to the relative abundance of information.
Assignment
On the attached geological time scale, fill out two important facts
for each period, four facts for the Precambrian era, and five for the
Cenozoic era. Use pages 347 – 359 in your text.