Geologic Time Scale

Geologic Time Scale

A record of the geologic events and life forms in Earth's history.

Eras

one of the three long units of geologic time between the precambrian and the present. (Eras: Palezoic, Mesozoic, Cenozoic)Mass extinctions mark boundaries between eras.

Periods

unit of time into which eras on the Geologic Time Scale are subdivided

(EX: Mesozoic Era is subdivided into the Triassic, Jurassic and Cretaceous Periods)

Precambrian

name for the time in earths early history that accounts for ninety percent of earth's time, but only cellular organisms lived

Paleozoic Era

it started with the cambrian explosion this is a time when a great number of organisms arose. During this time invertebrates developed along with vertebrates like fishes. Later animals began to reach land. Then the carboniferous period began and reptiles developed. Pangea formed and it ended with a mass extinction. This era lasted from 540 million years ago to 245 million years ago.

Mesozoic Era

The period of geologic time, from 250 million to 65 million years ago, during which gymnosperms were the dominant plants and dinosaurs the dominant vertebrates. Ended with extinction of the dinosaurs. Also called Age of Reptiles.

Cenozoic Era

The most recent period of geologic time, beginning 65 million years ago. during which mammals became the dominant vertebrates and angiosperms became the dominant plants. Also called Age of Mammals.

Invertebrate

An animal lacking a backbone, such as an arthropod, mollusk, annelid, etc.

vertebrate

an animal that has a backbone; includes mammals, birds, reptiles, amphibians, and fish

Mass extinction

event in which many types of living things become extinct at the same time

Eon

Longest time unit in the geological time scale, measured in billions of years.

Continental Drift

The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

Evidence of Continental Drift

-rock layers on coastlines of different continents match like a jigsaw puzzle, Land Features(mountain ranges on Africa and South America line up), Fossils(fresh water reptile fossils found on different sides of the world), Climate(fossils of tropical plants are now found on an island in the Arctic Ocean)

Pangaea

According to scientific theory, a single landmass that broke apart to form today's separate continents; thought to have existed about 200+ million years ago.