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EAS 210 > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

Relative Dating principles (7)

A
  1. Superposition
  2. Original horizontality
  3. Lateral continuity
  4. Cross-cutting relationships
  5. Inclusions and unconformities
  6. Contact metamorphism
  7. Fossil succession
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2
Q

Superposition

A

In a sequence of undeformed sedimentary rocks, each layer is younger than the one below. This also applies to lava and ash.

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3
Q

Original horizontality

A

Most sedimentary rocks form in horizontal layers. If layers are now inclined, then something happened after deposition and before today.

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4
Q

Lateral continuity

A

Layers of sediment initially extend laterally in all directions. Thus, rocks that are otherwise similar, but are now separated by erosional features, can be assumed to be originally continuous.

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5
Q

Cross cutting relationships

A

Intrusions are younger than the rocks they intrude, and a fault is younger than the rock that it has fractured.

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6
Q

Inclusions

A

Inclusions are fragments of one rock unit that are enclosed in another. The layer containing the inclusions must be younger than the inclusions.

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7
Q

Unconformities

A

Boundaries between an igneous rock and a sedimentary rock that represent missing time in the geological record.

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8
Q

Types of unconformities (3)

A
  1. Non-conformities (inclusions)
  2. Angular unconformities
  3. Disconformities (sub-parallel strata on each side)
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9
Q

Fossil succession

A

Distribution of fossils over time is not random, a distinct progression is observed. Index fossils are present in a wide geographic range and short time span.

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10
Q

Element

A

A substance composed of atoms that all have the same properties

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11
Q

Isotopes

A

Elements that behave the same chemically, but have different atomic mass numbers. Some isotopes undergo radioactive decay, and can be used for radiometric dating.

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12
Q

Radioactive decay

A

The process in which an unstable atomic nucleus is spontaneously transformed into an atomic nucleus of different elements. It is exponential.

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13
Q

Types of radioactive decay (3)

A

Alpha, beta, gamma

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14
Q

Rate of decay non-dependencies (3)

A

molecule/compound where the atom is located, pressure, temperature.

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15
Q

Parent atom

A

An atom before it undergoes any chemical change.

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16
Q

Daughter atom

A

The atom that remains after an original isotope has undergone radioactive decay.

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17
Q

Sources of Error in Radioactive Dating (2)

A
  1. Heat and pressure can cause the migration of parent and daughter atoms after crystallization. The most reliable dates are those obtained by using 2+ radioactive decay series in the same rock.
  2. Metamorphism can ‘reset’ the radiometric clock.
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18
Q

Measuring Radioactivity in rocks accuracy ranking

A
  1. Igneous (best)
  2. Metamorphic
  3. Sedimentary (worst)
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19
Q

Measuring radioactivity in rocks

A

Assuming a closed system (no atoms are added or lost), the clock starts when a grain crystallizes from magma. During cooling, radioactive parent atoms are separated from previously formed daughter atoms and incorporated into crystals. This process is most accurate from long-lived radioactive isotope pairs in igneous rocks. Measurements are made with a mass spectrometer via vaporization of the sample.
Beams of ions deflect with a magnet, heavier ions deflect less.

20
Q

Geological time scale

A

Relative boundaries defined by changes in type of rocks or fossils.

21
Q

Eons sequence (4)

A
  1. Hadean (oldest)
  2. Archean
  3. Proterozoic
  4. Phanerozoic (recent)
22
Q

Eons mnemonic

A

HAD ARCHaic PROfessional PHANtoms

23
Q

Hadean timespan

A

4567 - 4000 Ma

24
Q

Hadean eon

A

Early Earth, magma ocean cooled to form solid rock at the surface. Today, only rock grains from this time are preserved. “Like the underworld.”

25
Q

Archean timespan

A

4000 - 2500 Ma

26
Q

Archean eon

A

First continents form, out of igneous and metamorphic rocks. Earliest primitive life, single celled organisms (prokaryotes) in oceans. Photosynthesis begins, but there is no oxygen in atmosphere, since it all reacted with iron dissolved in seawater to form banded iron formations (BIF). “Beginning, origin”

27
Q

Proterozoic timespan

A

2500 - 542 Ma

28
Q

Proterozoic Eon

A

Plate tectonics similar to today, preserved rocks include all 3 types. Photosynthesis increases, free oxygen starts to accumulate in the atmosphere. Multicellular organisms develop, first plants and animals occur with snowball earth at the end. “Early life.”

29
Q

Phanerozoic timespan

A

543 Ma - Present

30
Q

Phanerozoic Eon

A

Start defined by the appearance of organisms with skeletons/hard shells.
5 major mass extinctions, oxygen levels remain high.
Divided into three eras and subdivided into periods. “Visible life.”

31
Q

Phanerozoic eras sequence (3)

A
  1. Paleozoic
  2. Mesozoic
  3. Cenozoic
32
Q

Phanerozoic eras mnemonic

A

Pals Meet Centaurs

33
Q

Paleozoic timespan

A

542 - 252 Ma

34
Q

Paleozoic era

A

Started by the appearance of animals with hard shells and the assembly of Pangea.
Ended by the biggest mass extinction in geological history. Divided into 6 periods.

35
Q

Mesozoic timespan

A

252 - 66 Ma

36
Q

Mesozoic era

A

Started by the biggest mass extinction in geological history. Appearance of mammals and dinosaurs, disassembly of Pangea, high sea levels. Ended by mass extinction caused by meteor impact/volcanic activity
Divided into 3 periods.

37
Q

Cenozoic timespan

A

66 Ma - Present

38
Q

Cenozoic era

A

Started by a mass extinction caused by meteor impact/volcanic activity.
Mammals develop, continents reach their current positions, formation of Alps, Himalayas, etc… The 6th mass extinction is underway. Divided into 3 periods, which are divided into epochs.

39
Q

Cenozoic period (1) and epochs (2)

A
  1. Quaternary period (the current ice age)
  2. Pleistocene epoch (start of ice age until the last retreat)
  3. Holocene epoch (Current inter-glacial interval)
40
Q

Time division sequence (4)

A
  1. Eon
  2. Era
  3. Period
  4. Epoch
41
Q

Precambrian eons (3)

A
  1. Hadean
  2. Archean
  3. Proterozoic
42
Q

Alberta rock origin times (3)

A

Quaternary, phanerozoic, Precambrian

43
Q

Alberta quaternary rocks

A

Ice age, layers of glacial, alluvial, surficial (soil) deposits.

44
Q

Alberta phanerozoic rocks

A

Sedimentary rocks of WCSB that thicken from east to west. Contains hydrocarbons and has a discontinuous record with unconformities.

45
Q

Alberta Precambrian

A

Igneous and metamorphic rocks in a crystalline basement. Archean and Proterozoic aged rocks.

EAS 210 (25 decks)

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