Intro to Geologic Time

Intro to Geologic Time

Geologic Time Scale

• a record of geologic events and the evolution of lifeforms as shown in the fossil record

• the divisions of this scale are used to date events in Earth's History

• begins when the Earth was formed and goes on until the present

How do we break down geologic time?

Eons ->

Era ->

Period ->

Epoch

Precambrian Time

• The earliest time span of Earth's History

Paleozoic Era

• Begins with early invertebrates - Trilobites and Brachiopods; continued developed vertebrate fish, then arachnids and insects; later came the first amphibians, and near the end of the Era Reptiles became dominant.

• Early land plants includes simple mosses, ferns, and cone bearing plants, and by the end of the Era, seed plants were common.

• The mass extinction that ended this Era caused marine invertebrates as well as amphibians to disappear.

• Formation of Pangaea.

Mesozoic Era

• Reptiles were dominant including various dinosaurs.

• Small mammals and birds appeared.

• Toward the end of the era, flowering plants appeared and the kinds of mammals increased.

• The mass extinction that ended the era caused the Dinosaurs to become extinct.

• A major geologic event of this Era was the break up of Pangaea.

Cenozoic Era

• New mammals appeared while others became extinct.

• The diversity of life forms increased.

• Flowering plants became most common.

• Humans are also part of the most recent period of this era.

• Present day earth is in this era.

• A major geologic event of the Cenozoic Era is the further splitting and moving of continents to their current positions.