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BIOS1013 - Environmental Geoscience > Lecture 1 - Key Concepts > Flashcards

Lecture 1 - Key Concepts Flashcards

1
Q

What methods can be used to study the interior of the Earth?

A

Magnetism

Inertia

Lower frequency seismic waves (main method).

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2
Q

What are P waves?

A

Primary waves are longitudinal waves.

They can travel through all mediums.

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3
Q

What are S waves?

A

Secondary waves are transverse waves.

They cannot travel through liquids.

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4
Q

How do geologists sort events in Earth’s history into a sequence of events?

A

By using numerical (absolute) ages or relative ages.

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5
Q

What is stratigraphy?

A

The study of the sequence of events in Earth’s history.

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6
Q

What information can each stratum provide?

A

The conditions of the Earth’s surface in the past.

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7
Q

What is uniformitarianism?

A

The idea that ‘the present is the key to the past’.

It was proposed by James Hutton.

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8
Q

What are two laws of stratigraphy?

A

The Law of Original Horizontality.

The Principle of Stratigraphic Superposition.

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9
Q

What is the law of original horizontality?

A

Water laid sediments are deposited in strata that are horizontal or nearly horizontal.

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10
Q

What is the principle of stratigraphic superposition?

A

Sedimentary strata are deposited from bottom to top.

This means that the youngest sediments are deposited on top of the older sedimentary rocks.

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11
Q

What is an unconformity?

A

A substantial break or gap in a stratigraphic sequence.

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12
Q

What are the three kinds of unconformity?

A

Angular unconformity.

Disconformity.

Nonconformity.

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13
Q

What is an angular unconformity?

A

Where older strata is deformed and then cut off by erosion. Younger layers are then deposited across them.

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14
Q

What is an example where there is an angular unconformity?

A

Siccar Point.

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15
Q

What is a disconformity?

A

An irregular erosion surface between parallel layers of strata.

This is difficult to identify and can only be seen by studying fossils.

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16
Q

What is a nonconformity?

A

Where younger strata overlie igneous or metamorphic rock.

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17
Q

What is the rock stratigraphic record?

A

Areas where there are distinctive strata that differ from those above/below it.

For example, Navaho Sandstone in the Zion National Park.

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18
Q

What is the time stratigraphic record?

A

Classification based on rocks formed within a specific time interval.

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19
Q

What is the primary unit of geological time?

A

A period.

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20
Q

What is a period?

A

The time during which a geological system accumulated.

21
Q

Is the geological record complete?

A

No, there may be gaps in an area. These gaps can be bridged by piecing together pieces of strata from nearby geographic areas.

22
Q

What is correlation?

A

The determination of equivalence in time-stratigraphic or rock-stratigraphic units of the succession of strata found in two or more different places.

23
Q

What can be used to aid correlation?

A

Volcanic ash layers.

Biostratigraphy (using fossils).

24
Q

What is the geological column?

A

A composite column that contains the succession of strata in chronological order.

25
Q

What is the geological column divided into?

A

Eons, eras, periods, epochs and stages.

26
Q

What is the largest interval of geological time?

A

Eons.

27
Q

What are the four eons?

A

Phanerozoic

Proterozoic

Archean

Hadean

28
Q

What is the Phanerozoic eon?

A

“Visible Life” - contains lots of evidence of past life.

29
Q

What is the Proterozoic eon?

A

“Earlier Life” - rocks contain evidence of multi-cellular organisms.

30
Q

What is the Archean eon?

A

“Ancient” - the oldest rocks on Earth that contain primitive microscopic life forms.

31
Q

What is the Hadean eon?

A

The earliest in Earth’s history. There is no rock record for this eon.

32
Q

What are eras?

A

Subdivisions of eons.

Only the Phanerozoic Eon is subdivided into eras.

33
Q

What are the three eras in the Phanerozoic Eon?

A

Cenozoic (“Recent Life”)

Mesozoic (“Middle Life”)

Palaeozoic (“Old Life”)

34
Q

What are eras divided into?

A

Periods.

35
Q

What are periods divided into?

A

Epochs.

36
Q

What are stages?

A

A subdivision of an epoch.

37
Q

What are isotopes?

A

An atom that contains a different number of neutrons.

38
Q

When was radioactivity discovered and what was its importance?

A

1896.

It provided a method of accurately determining the ages of rocks.

39
Q

What is a parent?

A

An atomic nucleus that undergoes radioactive decay.

40
Q

What is a daughter?

A

The product arising from the radioactive decay.

41
Q

What is radioactive decay measured in?

A

Half-lives.

42
Q

What six radioactive isotopes are used for radiometric dating?

A

Uranium-238
Uranium-235
Thorium
Rubidium
Potassium
Carbon

43
Q

What is the maximum number of half-lives that can occur before dating cannot occur?

A

6 half lives.

44
Q

What is radiocarbon dating used for?

A

Dating geologically young samples as the half life of carbon is short (5730 years).

45
Q

How is ¹⁴C created?

A

The bombardment of ¹⁴N by neutrons created by cosmic radiation.

1) A neutron is captured which causes a proton to be expelled forming ¹⁴C.

2) This then decays a β particle to form ¹⁴N.

46
Q

What is the Curie point?

A

The point at which the temperature is low enough for permanent magnetism to occur.

47
Q

What is the Curie point for magnetite?

A

580 Degrees Celsius.

48
Q

What is a magnetic chron?

A

A period in which the Earth’s polarity remains stable.

BIOS1013 - Environmental Geoscience (8 decks)

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