GEOLOGIC TIME SCALE
About how old is Earth?
4.6 billions years
What kind of isotopes do parent isotopes break down into?
Daughter isotopes.
Define relative dating.
Relative dating is used to find if one object or event is older or younger than another.
Define fossils.
Fossils are the traces or remains of organisms that lived long ago.
Climate
The weather conditions in an area over a long period of time.
What epoch do we currently live in?
Holocene
Define absolute dating
Absolute dating is a measure of the age of an event or object in years.
Explain the law of superposition.
The law of superposition states that an undisturbed sedimentary rock layer is older than the layers above it and younger than the layers below it.
Describe the ways organisms can be preserved as fossils.
Organisms become fossilized by being buried in rock, frozen, trapped in amber or asphalt, or petrified.
Ice core
A long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates.
What is uniformitarianism?
The same geologic processes have occurred in a uniform manner throughout geologic time, and the rate of change was relatively slow and constant.
Define index fossil.
An index fossil is a fossil that is distinct, abundant, and widespread for only a short period of geologic time.
Define unconformity.
An unconformity is a gap in the geologic record caused by erosion or a pause in deposition.
List examples of trace fossils
Trace fossils include tracks, burrows, and coprolites.
Geology
The scientific study of the origin, history and structure of the Earth and the processes that shape Earth.
What is catastrophism?
Sudden, rapid, and devastating geologic processes brought about geologic change.
Explain radiometric dating
Radiometric dating is used to determine an object’s age by comparing the percentages of parent and daughter isotopes.
Explain how scientists can use fossils to determine the relative age of rock layers.
A rock layer that contains a fossil of an earlier life form is relatively older than a rock layer that contains a fossil of a more recent life form.
Describe and give evidence for the movement of continents over time.
The continents have been moving throughout Earth’s history. At one time, they formed a single landmass, which is evident by the shapes of continents and the distribution of rock types, mountains, and fossils.
Unconformity
A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long time.
What is the geologic time scale?
The method used to divide Earth's History into parts.
How can we determine how old Earth is?
Earth’s age has been determined by using radiometric dating techniques on rocks from the moon and from other parts of the solar system, such as meteorites, that were formed when the solar system was forming.
Define geologic column.
A geologic column is an ordered arrangement of rock layers based on their relative ages that is used to identify the relative ages of rock layers that are located in different regions.
List types of evidence that support that Earth’s climate has changed over time.
Ice cores, sea-floor sediments, and tree rings provide evidence that Earth’s climate has changed over time.
Geologic column
An ordered arrangement of rock layers that is based on the relative ages of the rocks- older at the bottom, younger at the top.