Geologic time Flashcards Preview

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Flashcards in Geologic time Deck (18):
1

3 Eons

Archean, protozoic, Phanerozoic

2

3 eras in the Phanerozoic

Paleozoic, Mesozoic, Cenozoic

3

12 Periods in order

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene, Quaternary

4

Age of the earth

4.55 Ga

5

Age of base of Phanerozoic

541 Ma

6

End Paleozoic date

252 Ma

7

End Mesozoic Date

66 Ma

8

Faunal Succession and 5 Major Mass Extinctions during the Phanerozoic Eon

End-Ordovician
Late Devonian Crisis
Permo-Triassic Extinction (“The Great Dying”)
End-Triassic Extinction
End-Cretaceous Extinction - huge asteroid hits earth.

9

Phanerozoic Eon: Three Evolutionary Faunas of Marine Animals (Cambrian, Paleozoic, & “Modern”)

Trilobites
Inarticulate brachiopods
Archaic mollusks and primitive crinoids

10

Establishing age relationships of sedimentary rocks

using radiometric dating of zircons and crosscutting relationships

11

what is an isotope?

An element which contains a different number of neutrons.

12

What is radioactive decay?

When a neutron releases an electron and becomes a proton.

13

What is a half-life?

The amount of time in which half of the parent isotopes to decay into daughter isotopes

14

Parent-Daughter isotope ratios

The parent isotope is the original isotope, and the daughter isotope is the isotope which the parent isotope decays into.
Tells us, along with the half life, what the age of the rock is

15

How do geologists figure out the numeric age of a rock? (What do they need to know to do this?)

The parent-daughter isotope ratios and the half life.

16

Clair Patterson (Age of the Earth – why did he have to use meteorites?)

He made two correct assumptions- that the meteorites were leftover materials from the beginning of the solar system and that they would maintain an unchanged internal chemistry.

17

Igneous Rocks = zircons

zircons are like time capsules in rocks. they help measure the age.

18

Bentonite layers (volcanic ashes) as marker beds

Can use crosscutting relationships and principle of superposition along with radiometric dating to determine the age of shale.