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EAS100 > TIME AND TECTONICS IN GEOSPHERE > Flashcards

TIME AND TECTONICS IN GEOSPHERE Flashcards

1
Q

when was the geologic time scale developed?

A

1800

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2
Q

when was radioactivity discovered and its definition

A
  • 20th century
  • measurment of geologic time
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3
Q

description and principle

stratigraphy

A
  • relative age dating for sedimentary rock
  • 18th century basic principles from observing layers of sedimentary rock
    1. correlation
    2. order of strata
    3. cross cutting
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4
Q

correlation by lithology

A
  • comparing sucessions of layers in different places
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5
Q

description and example, a date

correlation by fossils

A
  • correlating strata based on fossils
  • its characteristics are adundancy, a wide distribution, marine and rapid evolution
    *abundant in paleozoic
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6
Q

description and example

cross cutting relationships

A
  • events that modify rocks after deposition
  • show relative age of features
  • examples are uncomformities, faults, igneous intrusions
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7
Q

dykes and inrusions are..

A

are younger than the host rocks

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8
Q

precambrian division of eons

A

protozeroic, archean, hadean

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9
Q

how is the phanerzoic eon divided

A
  • fossil investigations
  • superposition
  • cross cutting
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10
Q

order of strata

A
  • sedimentary rocks thatrecord environmental change
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11
Q

the sucession of sedimentary layers is illustrated in..

A

stratigraphic columns

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12
Q

absolute time method

A

isotopic dating

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13
Q

isotopic dating -neurons

A
  • neurons play a role in binding the nuckeus together
  • the number of neutrons can vary- it defines
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14
Q

radioactive decay

A

*unstable isotopes decay to create stable isotopes
* so nucleus breaks apart and undergoes decay, and creates a new element randomly
* the rate is predictable
* used for measurement of geologic time

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15
Q

radioactive decy-

half life

A

the time for half the atoms of an isotope to decay
* after 2 half lives, a quarter of atoms are left

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16
Q

radioactive decay-

daughter atoms

A
  • the new element of the decay
17
Q

requirements of age determination

A
  • half life or decay constant
  • final amount of parent isotope
  • og amount of parent isotope or final amount of daughter isotope
18
Q

when did the great oxygenation event occur

A

2.45 ga - 2.2 ga

19
Q

when was the emergence of photosynthesis

A

1.25 ga

20
Q

oceanic crust make up

A
  • mafic igneous rock
  • basalt
21
Q

continental crust

A
  • igneous, sedimentary, metamorphic
  • intermediate - felsic composition
22
Q

hypotheis date

contental drift date

A

1914

23
Q

gravity and the asthenosphere

A
  • stronger attraction to denser rocks close to the surface
  • measure of gravity is all objects attract each other according to mass
    *
24
Q

what started the theory

theory of isotasy

A
  • mtns are underlain by lighter rocks / asthenosphere
25
Q

asthenosphere

A
  • The layer of the mantle lying beneath the lithosphere and capable of plastic flow
  • can allow plate movement to occur
26
Q

lithosphere

A
  • division of plates above the asthenosphere\
  • undergoes vertical isostatic rebound after ice melts
27
Q

dipole field

A

The magnetic field produced by a magnetized body with north and south poles on opposite sides

28
Q

magnetism

A
  • the magnetic core of earth suggests it is circulating liquid iron
    *
29
Q

declination

A
  • The direction relative to the north of Earth’s magnetic field.
  • indicates direction to the pole
30
Q

inclination

A

The steepness of Earth’s magnetic field/ of the declination
* indicates distance from the pole

31
Q

paleomagnetism

A
  • The study of preserved magnetism in ancient rocks
  • when magnetite cools it is magnetized by the surrounding megnetic by the earths field
32
Q

remnant magnetism

A
  • magnetite rocks form and make a record of the earth magnetic field as it existed at the time of their formation, so
  • RM determines the ancient location of the N or S pole relative to rocks as currently found
33
Q

MAGNETIC REVERSALS

A

reversal of N and S poles
recorded by remnant magnetism

34
Q

MAGNETIC ANOMOLY

A

field slightly stronger or weaker than normal
* result from remnant magnetism acquired during spreading of ocean floor while magnetic reversals occured
* determines age of ocean floor

EAS100 (8 decks)

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