Geologic Time Flashcards

(41 cards)

1
Q

Relative Dates

A

Sequence of Formation (non numerical dates)

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2
Q

Principle of Superposition

A

•In an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below

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3
Q

Principle of Inclusiuon

A

Fragments of one rock unit enclosed within another rock unit; rock containing inclusion is younger

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4
Q

Unconfirmity

A

brteak in rock record produced by nodeposition and erosion of rock units

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5
Q

Angular Unconformity

A

Tiled rocks are overlain by flat-lying rocks

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6
Q

Isotope (2)

A

Different neutron number/mass number (total)

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7
Q

Disconformity

A

Sedimentary Strata at either side of the nonconformity are parallel

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8
Q

Nonconformity

A

Sedimentary Strata overlay metamorphic or igenous rock

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9
Q

Principles of Faunal Succession

A

so known as the law of faunal succession, is based on the observation that sedimentary rock strata contain fossilized flora and fauna, and that these fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances.

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10
Q

Index Fossils

A

Widespread geographically, limited to short period of geologic time

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11
Q

Fossil Assemblages

A

Can be used to identify a r rock bed that does not contain and index fossil

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12
Q

Metamorphic Grade

A

Degree to which parent rock changes: progress from low grade (temp, pressure) to high grade (temp, pressure)

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13
Q

Metamorphic rock Definition

A

transition of one rock to another by temperatures or pressures unlike those in which it was form. Changes in minerology from parent rock

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14
Q

Parent Rock->Metamorphic Rock (2)

A

Pressure/Heat

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15
Q

Foliation

A

Describes any planar arrangement of mineral grains or structural features within a rock

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16
Q

Correlation

A

Matching of rocks of similar ages from different regions: position of bed in a sequence of strata: match rocks of similar ages from different regions

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17
Q

Principle of Fossil Succession

A

states that fossils are arranged according to their age

18
Q

Fossil Succession Examples

A

Age of Triboilites, Fishes, Repitiles, Mammals

19
Q

Shells of Organisms

A

can be used to infer positions of ancient shorelines and seawater temperatures

20
Q

Corals

A

can be used to indicate former temperature of the water

21
Q

daughter products

A

Isotopes resulting from the decay of a parent are termed the

22
Q

parent

A

unstable radioactive isotope

23
Q

Parent:Daughter

A

The ratio between parent and daughter isotopes in a rock is used to determine its numerical age

24
Q

PArent:Daughter = 1:1

A

Half life passed

25
Stable
Daughter Isotope
26
sedimentary rocks can rarely be dated by radiometric means so...
geologists must rely on igneous rocks in strata
27
Bracketing episodes in earth's history
relative dating from igneous to sedimentary rocks
28
Disconformity between
horizontal sedimentary
29
Nonconfrmity between
younger sedimentary and older igenous/metamorphic
30
Principle of Cross Cutting
Faults/Intruions within (DIKES) are younger
31
Xenolith
•When magma intrudes a rock mass, blocks of that rock may become dislodged and incorporated into the magma
32
Uplift and Erosion followed by
angular unconformity (subsidence and renewed deposition)
33
Beta emssion
•beta particle ejected from the atom
34
Beta particle
election
35
Alpha Emission
alpha emmited
36
alpha particle
two protons/two neutrons
37
Electron Capture
electron captured combines with proton to become neutron
38
Conformable layers
no break in rock record
39
flat layers
not deformed
40
rock layers that are deformed
deformed after deposition
41
Principle of Lateral Continuity
* Beds originate as continuous layers that extend in all directions until they eventually thin out or grade into a different sediment type * When a river carves a canyon, we can assume that similar strata on either side were once connected across the span of the canyon