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Mrs. Welborn - Geologic Time
Key terms, fossils, etc.
24
Science
8th Grade
02/23/2011

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Term
Precambrian
Definition
The largest Geological part of earth's history .
Term
Geologic Time Scale
Definition
The division of earth's history into time units .
Term
Eras
Definition
Major subdivisions of Geological time based on differences in life-forms .
Term
Species
Definition
A group of organisms that normally reproduce with other members of their group .
Term
Trilobites
Definition
Organisms that lived hundreds of millions of years ago with bodies divided into three sections .
Term
Periods
Definition
Major divisions of an era .
Term
Pangaea
Definition
The single landmass the once contained all Earth's continents .
Term
Birds
Definition
Flying animals that evolved from dinosaurs .
Term
Jurassic
Definition
The time period where dinosaurs were the dominant life-form .
Term
Epoch
Definition
Smaller units of time in a geologic period .
Term
Unconformity
Definition
Any gap left in a rock record .
Term
Fossils
Definition
The remains, imprints, or traces of prehistoric organisms .
Term
Carbonaceous Film
Definition
The thin film of carbon the shows the outline of an organism .
Term
Mold
Definition
the fossils in which the spaces inside are filled with minerals from ground water .
Term
Absolute age
Definition
The age, in years, of a rock or other object
Term
Relative age
Definition
Is somethings age in comparison to something else.
Term
Half-Life
Definition
the time it takes for half of the atoms in an isotope to decay .
Term
Radioactive decay
Definition
is the breaking down of some isotopes into other isotopes and particles .
Term
Super position
Definition
principle that says if rocks are undisturbed, older rocks are under younger rocks .
Term
Radio metric dating
Definition
is a method used to calculate the absolute age of a rock .
Term
remains
Definition
cavity in rock form which an organism had decayed .
Term
Uniformitarianism
Definition
The principle that Earth process occurring today are similar to those that occurred in the past
Term
Cast
Definition
fossil created when a sediment fills a mold and hardens .
Term
Index
Definition

a fossil that the remains of an organism that lived during a specific time that is used to define the age a of a particular rock layer .

 

fossils forn a species that existed on earth for a short period of time

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