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Geological Oceanography > Geologic Time > Flashcards

Geologic Time Flashcards

1
Q

Uniformitarianism

A

The physical, chemical and biological laws that operate today have also operated in the geologic past. So forces and processes that shape planet have been occurring for very long time. Put forth in late 1700s by James Hutton

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2
Q

Relative dating

A

Placing rocks and events in a relative sequence

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3
Q

Principles of relative dating

A

Law of superposition
Principle of original horizontality
Principle of cross-cutting relationships
Inclusions

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4
Q

Principle of superposition

A

In an informed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it.
Oldest rocks on bottom

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5
Q

Principle of original horizontality

A

Sediments are deposited horizontally by gravity

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6
Q

Principle of cross-cutting relationships

A

When a fault cuts through other rocks, or when magma intrudes and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected

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7
Q

Inclusions

A

Fragments of one rock contained within another (rock containing inclusions is younger)

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8
Q

Conformable layers of rocks

A

Deposited essentially without interruption

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9
Q

Uncomformity

A

Long period of time during which deposition ceased, erosions removed previously formed rocks, and then deposition resumed. A break in the rock record.

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10
Q

Angular unconformity

A

Consists of tilted or folded sedimentary rocks overlain by younger flat lying strata
Indicates that period of deformation and erosion occurred

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11
Q

Disconformity

A

Strata on either side are parallel or conformable

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12
Q

Nonconformity

A

Older metamorphic or intrusive igneous rocks below younger sedimentary rocks

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13
Q

Correlation of rock layers

A

Matching rocks of similar age in different regions.
Often relies upon fossils (across continents)
Lithologies (noting position of layers of rock in a sequence of strata)

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14
Q

Fossils

A

Remains or traces of prehistoric life in sediment and sedimentary rocks

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15
Q

Principle of fossil/faunal succession

A

Fossil organisms succeed one another in a definite and determinable order and therefore any time period can be recognized by its fossil content

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16
Q

Index fossils

A

Wide spread geographically and are limited to a short span of geologic time so their presence provides an important method of matching rocks of the same age

17
Q

Catastrophic

A

Earths varied landscapes formed primarily by great catastrophes
Believed during 1600s and 1700s b/c people thought (James ussher) that earth was only a few thousand years old

18
Q

Radioactivity

A

Spontaneous breaking apart (decay) of unstable atomic nuclei.

19
Q

Alpha particles

A

May be emitted from nucleus
Consists of 2 protons and 2 neutrons
Emission means: mass number of isotope is reduced by 4 and atomic number decreased by 2

20
Q

Beta particles

A

Or electron is given off from nucleus
Mass number remains unchanged because electrons have basically no mass
Emissions causes 1 more proton so atomic number up by 1

21
Q

Electron capture

A

More rare, upper atmosphere
Sometimes electron captured by nucleus
Electron combines with proton and forms another neutron
Mass number unchanged but atomic number decreased by 1

22
Q

Parent isotope

A

Unstable radioactive isotope

23
Q

Daughter products

A

Isotopes resulting from decay of the parent

24
Q

Radiometric dating

A

Using radioactivity as a reliable method for calculating the ages of rocks and minerals that contain particular radioactive isotopes

25
Q

Half-life

A

The time required for one half of the nuclei in a sample to decay

26
Q

Radiocarbon dating

A

Dating recent events with the radioactive isotope of carbon which is carbon-14

27
Q

Geologic timescale

A

Divides geologic history into units. Originally created using relative dating

28
Q

Eon

A

Greatest expanse of time

4 eons: Phanerozoic, Proterozoic, Archean, Hadean

29
Q

Era

A

Eons divided into eras

Three eras in Phanerozoic are Paleozoic, Mesozoic, Cenozoic

30
Q

Periods

A

Each era in Phanerozoic eon divided into units known as periods
Paleozoic has 7
Mesozoic and Cenozoic have 3

31
Q

Epochs

A

Each period divided into epochs
Seven epochs for the periods of Cenozoic era
Epochs of other periods not usually specific names but terms early, middle and late

32
Q

Precambrian

A

4bn years prior to Cambrian divided into two eons, Archean and Proterozoic, which are divided into four eras

Geological Oceanography (10 decks)

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