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More of Earth's History


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a break or gap in the rock record
In undistributed layers of rock where are the oldest layers?
at the bottom
What are some evidence of events on earth?
igneous intrusions and extrusions
faults, joints, folds
internal characteristics
What isotopes are useful in dating?
What steps combine in seqwuence to produce an unconformity?
uplift, erosion, subsidence, and depostition
What are the ages of rock compared to their surronding?
rock fragments found in larger rock masses are older the n surronding rock
cracks viens and mineral cement are younger then surronding rock
What are the perferable types of index fossils?
lived over the entire earth for relatively short periods of time
What is the most reliable fossil evidence?
index fossils
a mineral deposit that has filed a crack
What isotope does not combine chemically with any other element?
argon 40
What species first occured in the Paleozoic era?
intervertebrates, fishes, amphibians, vertebrates, and land plats and animals
Why are unconformities useful?
they indicate a geologic event of some magnitude took place
Explain the history of the atmosphere
500 million years ago the earth's interior was solid, earth heated and melted the solid materials, as earth cooled the crust developed
interfaces formed when sedimentary rocks are deposited on top of an eroded surface of igneous rocks
How can potassium 40 be used to date a rock?
by comparing the amounts of argon 40 and potzassuium 40, the age can be determined
When using the potasium- argon dating system which determines the age of the rock?
The more Agron 40 in the rock, the older the rock
How was earth born?
as a cloud of gases and dust left over fro m the creation of the sun
What was the primary source of gases of Earth's earliest atmosphere?
outgassing by volcanoes.
How long have have humans been in existence?
.04% of the 4.5 billion years
What does the mesozoic era provide evidence of?
dinosaurs, earliest birds and mammals
What is necessary for fossils to survive?
must be buried soon after death and have hard shells, bones,m or teeth
angular unconformities
tilted, folded,or faulted rocks that have been eroded and covered again
what determines the geographic history of an area?
fossil evidence
age of rocks
erosional record
parallel unconformities
occur when parallel rock layers of different ages are seperated by an erosional surface

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