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Geologic Time

Approximately how old is the earth? 4.6 bya
When did the earliest life form appear? 3.9 bya
What is the law of superposition? new rock layers are deposited on top of already existing rook pushing older rocks down
What process gives us the absolute date of rocks? radiometric dating
What does the Geologic Time Scale represent? the entire history of the Earth since its formation
What is a characteristic of the Pre-Archean? no evidence of life
What life form evolved during the Archean? first single-celled organisms evolved
What three eras make up the Phanerozoic Eon? What does each name mean? Paleozoic-"ancient life" Mesozoic-"middle life" Cenozoic-"recent life"
What is the largest unit of geologic time? eon
What is a subdivision of periods on the geologic time scale? epoch
Mass extinctions are marked by sudden changes in this? fossil record
What is the disappearance of many species within a short period of time? mass extinctions
What is a large division of geologic time, but smaller than an eon? era
Who is a scientist who studies the earth's crust as well as the processes and history that shaped it? Geologist
Who is a scientist that studies fossil remains found on the Earth's surface in order to study primitive life form such as: plants, animals, fungi and bacteria Paleontologist
Geologists assume the _____________________________ rock layers are on ____________________ of the ___________________ ones, unless some type of disturbance occurs. newest; top; oldest
The strata of sedimentary rocks is important in determining their ________________ age. relative
Relative age determines the "relative" order of past events but not the _____________. absolute age
Strata is sometimes _______________. disturbed
What are preserved remains or traces of animals, plants, and other organisms from the remote past? fossils
What are special fossils that geologists use to indicate the boundaries in geological time? index fossils
What are the 4 characteristics of index fossils? -easily recognizable -abundant -wide geographic location -short life span
If two different rock strata in different areas on Earth contain the same index fossils, the the strata are probably the same ___________________________. age
What is the most accurate form of dating called? radiometric dating
Absolute age relies on the property of _______________________, which is the ________________________ an element takes to decay. half life; predictable time
What is the geologic time scale based on? rock strata and fossil record
The geologic time scale is broken into different time chunks, the largest being the Eon, then ________________, then ___________________, and finally Epoch. Era; Period
How much of the earth's geologic history falls into Precambrian? 88%
In any undisturbed sequence of strata, the oldest layer is at the bottom of the sequence, and the youngest layer is at the top. What law is this? The Law of Superposition
Any feature that cuts across a body of rock of sediment or rock is youngest than the body of sediment or rock that it cuts across. What law is this? The Cross-Cutting Law
If one rock body contains fragments of another rock body, it must be younger than the fragments of rock it contains OR...... the inclusions are older than the rocks which contain them. What law is this? The Law of Inclusions
Created by: dancer2024