Absolute and Relative Dating Flashcards

1
Q

how did early scientists explain geologic changes on earth

A

catastrophism

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2
Q

the principle that states that all geologic change occurs suddenly.
* Supporters of this thought that Earth’s features, such as mountains and seas, formed during sudden events called
catastrophes.

A

catastrophism

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3
Q

About 250 years ago, James Hutton established
a principle that is now known as

A

uniformitarianism

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4
Q

the idea that the same geologic processes that shape Earth today have been at work throughout Earth’s history
- The principle also states that the average rate of geologic change is slow and has remained relatively constant over time. (weathering, erosion, deposition, magmatism/volcanism, metamorphism, diastrophism, deformation (joints, fault, fold), earthquake)
- helps further understand what happened in the past

A

uniformitarianism

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5
Q

true/false

  • Today, geologists realize that neither uniformitarianism nor catastrophism alone accounts for all geologic change. It is the combination of the two ideas.
  • While most geologic change is gradual and uniform,
    catastrophes do cause some geologic change.
  • For example, earthquakes, floods, volcanic eruptions, and asteroid impacts can cause sudden changes to Earth’s surface.
A

true

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6
Q

how do we tell the age of rock

A

through relative and absolute dating

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7
Q

what type of dating

  • Relative age: comparing which is younger or
    older; Qualitative
  • the science of determining the relative order of past events, w/o necessarily determining their absolute age
  • used to arrange geological events, and the rocks they leave behind in a sequence
  • utilizes laws of statigraphy
A

relative dating

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8
Q

branch of geology concerned with the order and relative position of strata and their relationship to the geological time scale
- analysis of the order and position of layers of archaeological remains

A

statigraphy

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9
Q

what is the term for each stripe of rock

A

layer/rock stratum/strata

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10
Q

How are rock strata formed?

A
  • weathering and erosion (happens above water, when there is an uplift in the form of faults and folds)
  • deposition
  • Sedimentation- Compaction and Cementation
    (Lithification; happens underwater)
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11
Q

the process that loose and underconsolidated Sediment particles transform into hard and solid rocks. This process includes a number of geological processes, such as consolidation, deep bury, cementation, recrystallization and dehydration.

A

lithification of sedimentary rocks

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12
Q

“lithification” of igneous rocks

A

cooling/crystallization of magma/lava

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13
Q

“lithification” of metamorphic rocks

A

metamorphism (heat, pressure, protolith, liquid)

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14
Q

principles of stratigraphy

A
  • Law of Superposition
  • Law of Original Horizontality
  • Law of Lateral Continuity
  • Law of Cross-cutting Relationships
  • Law of Inclusion
  • Law of Fossil Succession
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15
Q

principle of stratigraphy

a major principle of stratigraphy stating that within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence.

A

law of superposition

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16
Q

principle of stratigraphy

suggests that all rock layers are originally laid down (deposited) horizontally and can later be deformed. (due to gravity)
- parallel to the horizon
- deposition first before deformation

A

law of original horizontality

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17
Q

principle of stratigraphy
- states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous. As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.
- materials forming any stratum were continuous unless some other bodies/erosion & weathering/endogenic (appeared after deposition) processes stood in the way

A

principle of lateral continuity

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18
Q

principle of stratigraphy

Any geologic feature that crosscuts or modifies another feature must be younger than the rocks it cuts through. The cross-cutting feature is the younger feature because there must be something previously there to cross-cut.

A

principle of cross-cutting relationship

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19
Q

principle of stratigraphy

any rock fragments that are included in a rock must be older than the rock in which they are included
- for any material to be included within the rock, it must have been present the time the rock layer was being lithified
- once a rock is lithified, no other material can be deposited within its internal structure

A

principle of inclusion

20
Q

principle of stratigraphy

law of superposition, but fossils
- using this, one can determine stratigraphic succession - the order in which units of rock were deposited over time

A

principle of fossil succession

21
Q

group of fossils

A

fossil assemblages

22
Q

who proposed the first three of the principles of stratigraphy

A

nicolas steno

23
Q

a break in the rock record produced by erosion and/or nondeposition of rock units
* Represents “lost time”; a geologic mystery
- may disturb stratification of rocks

A

unconformities

24
Q

types of unconformities

A

angular unconformity, disconformity, nonconformity, paraconformity

25
unconformity rocks get tilted by deformation and are overlain by flat-lying rocks - tilting, folding, faulting - rocks change the angle
angular unconformity
26
unconformity - strata on either side of the unconformity are parallel but irregular due to erosion - somehow it conforms - eroded layer in the middle, may look continuous
disconformity
27
unconformity - metamorphic or igneous rocks come in contact with sedimentary strata to folding or uplifting - not at all
nonconformity
28
unconformity - overlying rocks are parallel and continuous to the previous one - as if almost - multiple similar layers - hard to tell the boundary of each time
paraconformity
29
Numerical age; estimated age; Quantitative * makes use of Radiometric Dating- Half life of Radioactive Isotopes
absolute dating
30
calculates an age in years for geologic materials by measuring the presence of a short-life radioactive element - The ratio of radioactive isotopes and the daughter is taken to estimate the age of materials
radiometric dating
31
the time required for half of the atoms in a sample to decay to daughter atoms - rate of decay
half-life
32
The ratio of carbon-12 to carbon-14 is the ______ in all living things. * At the moment of death, the amount of________ begins to decrease because it is unstable, while the amount of ___________ remains constant in the sample
same; carbon-14;carbon 12
33
carbon 14 decays into
nitrogen-14
34
half life of carbon-14
5730 years
35
who proposed the innovative method for dating organic materials by measuring their content of carbon-14
willard libby
36
time limit of c-14 dating
approx. 50000 years
37
is c-14 accurate
it may not be someday as fossils disturb this by carbon emmissions
38
limitations of radiometric dating
isotopes may not be found in some rocks/fossils
39
daughter and half life of al-26
mg-26; 740 thousand
40
daughter and half life of I-129
xe-129; 17 million
41
daughter and half life of U-235
(lead) Pb-207; 704 million
42
daughter and half life of K-40
Ar-40; 1.3 b
43
daughter and half life of U-238
Pb-206; 4.5 b
44
daughter and half life of Th-232
Pb-208; 14 b
45
daughter and half life of (rubidium) rb-87
sr-87; 49 b
46
decay of uranium and thorium isotopes, aside from lead, also yields
helium
46
decay of uranium and thorium isotopes, aside from lead, also yields
helium