Section 1: Geologic Time
VocabularyGeologic Column - An ordered arrangement of rock layers that is based on the relative ages of the rocks, in which the oldest rocks are at the bottom.
Era - A unit of geologic time that includes two or more periods. Period - A unit of geologic time that is longer than an epoch but shorter than an era. Epoch - A subdivision of geologic time that is longer than an age but shorter than a period. |
Key Concepts
- Each period of time is characterized by specific fossils.
- The geologic column is used to determine the relative age of sedimentary rock.
- Geologic time is divided into eons, eras, periods, epochs, and ages.
Section 2: Precambrian Time and the Paleozoic Era
Vocabulary
Evolution - A heritable change in the characteristics within a population from the generation to the next; the development of new types of organisms from pre-existing types of organisms over time.
Precambrian Time - The interval of time in the geologic time scale from Earth’s formation to the beginning of the Paleozoic Era, from 4.6 billion to 542 million years ago.
Paleozoic Era - The geologic era that followed Precambrian Time and that lasted from 542 million to 251 million years ago.
Shields - Large areas of exposed Precambrian rock.
Precambrian Time - The interval of time in the geologic time scale from Earth’s formation to the beginning of the Paleozoic Era, from 4.6 billion to 542 million years ago.
Paleozoic Era - The geologic era that followed Precambrian Time and that lasted from 542 million to 251 million years ago.
Shields - Large areas of exposed Precambrian rock.
Key Concepts
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Section 3: The Mesozoic and Cenozoic Era
Vocabulary
Mass Extinction - An episode during which large numbers of species become extinct.
Mesozoic Era - The geologic era that lasted from 251 million to 65.5 million years ago; also called the age of reptiles.
Cenozoic Era - The current geologic era, which began 65.5 million years ago.
Cenozoic Era - The current geologic era, which began 65.5 million years ago.