There are four geologic eras defined as a means to study Earth and what shaped our planet as it is today. It has been said that the record for these eras span the 4.6 billion-year record of the history of Earth. These four geologic areas are as follows: The Precambrian Era, Paleozoic Era, Mesozoic Era and Cenozoic Era. These eras are subdivided into the following periods:
1. Precambrian Era which is the beginning of Earth. This is divided into three periods:
a. Hadean Period
b. Archean Period
c. Proterozoic Period
2. Paleozoic Era which is considered to be the age of ancient life which is 248-544 million years ago. This era has six periods:
a. Cambrian Period
b. Ordovician Period
c. Silurian Period
d. Devonian Period
e. Carboniferous Period
f. Permian Period
3. Mesozoic Era which covers the reign of all dinosaurs on Earth and other life forms. This era has three periods:
a. Triassic Period
b. Jurassic Period
c. The Age of Dinosaurs
4. Cenozoic Era which is the era which covers the time of mammals on Earth. This era is divided into two periods:
a. Tertiary Period which is divided into two series:
i. The Great Ice Age
ii. Holocene
b. Quaternary Period which is divided into five series:
i. Paleocene
ii. Eocene
iii. Oligocene
iv. Miocene
v. Pliocene
Cenozoic, mesozoic, paleozoic, precambrian 2. same mountains on both sides of the atlantic ocean 3. found same fossils of plants and animals in both continents.