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10 Cards in this Set

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What is the geologic time scale
The division of Earth history into blocks of time-eons, eras, periods, and epochs; the time scale was created using relative dating principles. The major units of the time scale were described during the nineteenth century
What types of subdivisions of the geologic time scale, from longest to shortest expanse of time
eon, era, period, and epoch
The eon called the what began about 540 million years ago
phanerozic
what eras is the Phanerozoic divided into
Paleozoic, Mesozoic, and Cenozoic
Is it true or false that periods such as the Tertiary are characterized by more profound life-form changes that those of eras
false
is it true or flase that the Precambrian represents a much longer part of Earth's history than the Phanerozoic
true
Why do geologists known so little about Precambrian history
?
What is one reason why radiometric dating of sedimentary rocks is rarely accurate
a
Circle the letter of one reason why radiometric dating of metamorphic rocks is rarely accurate
b
Geologists usually assign numberical dates to sedimentary rock layers by relating them to what rock masses that can be dated
c