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Glaciations > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

How does the “Law of superposition” determine whether something is younger or older than something else?

A

By grouping sediment layers, fossils, artifacts, or landforms. It is a relative dating method

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2
Q

How does the degree of weathering tell which landscape surface is older and which is younger?

A

All landscape surfaces are subject to weathering processes that lead to physical and chemical alteration of surficial deposits.

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3
Q

What is incremental layer dating?

A

It is a dating technique based on the annual addition of material to organic tissue or to sequences of sediment.

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4
Q

What is clay varve chronology?

A

Sequences deposited in lakes or sea, close to retreating ice margin. Layering depends on the seasonality of deposition relating to grain sizes, organic content, calcium content, etc.

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5
Q

What is dendrochronology?

A

Sequences of tree ring thicknesses depending on annual local/regional climate.

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6
Q

How can radiocarbon dating indirectly date glacial sediment?

A

By dating organic remains

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7
Q

What is the most common use of radiocarbon dating in paleo glaciology?

A

Dating “dead” organic material on terrestrial lake sediment to make deglaciation chronologies.

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8
Q

Where does radiocarbon dating work best?

A

In a temperate environment with plenty of organic material present during periods after glaciation.

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9
Q

Are there many uncertainties associated with radiocarbon dating?

A

No

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10
Q

How does radiocarbon dating determine the age of an object?

A

By determining the time elapsed since the death of the organism, the material was derived from (plants, animals, and microorganisms).

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11
Q

How do we ascertain when an organism died using the radiocarbon dating?

A

By measuring the ratio between Carbon14 to Carbon 12. This is done because upon death, Carobon14 is no longer absorbed, and it starts to decay. The older the organism is, the less Carbon14

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12
Q

How old can the oldest organisms dated by the Carbon14 method be?

A

No more than 40 thousand years, due to the short half-life of Carbon14.

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13
Q

What do uncalibrated ages refer to in radiocarbon dating?

A

Radiocarbon age in thousands of years before 1950 AD that is not calibrated with incremental datasets such as tree rings or corals.

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14
Q

What does Cosmogenic Nuclide dating determine in glaciology?

A

The rates of glaciers and ice-sheet thinning and recession.

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15
Q

What is the most common application of cosmogenic nuclide dating?

A

To date when glacially transported boulders emplaced on top of end moraines or glacially eroded bedrock was exposed to sunrays

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16
Q

Why is Cosmogenic Nuclide Dating good for glacial environment?

A

Since it works without needing organic material

17
Q

What are the most common samples used in Cosmogenic Nuclide dating?

A

Quartz and whole rock samples

18
Q

What are Cosmogenic Nuclides?

A

Rare isotopes that form in surface rock because of bombardment by high-energy cosmic rays.

19
Q

How can scientists calculate how long rocks have been exposed at the earth’s surface with Comic Nuclide dating?

A

By counting the number of Cosmic Nuclide isotopes as a ratio to other isetopes

20
Q

What do the largest uncertainties in Cosmic Nuclide dating involve?

A

The unknown geologic history of the sample and whether the sample has experienced prior or incomplete exposure.

21
Q

If the sample has been priorly exposed, how can age estimation in Cosmogenic Nuclide dating be wrongly estimated?

A

The age can be overestimated

22
Q

How can the age be underestimated in Cosmogenic Nuclide dating?

A

If the sample has been incompletely exposed.

23
Q

How can Optically Stimulated Luminescence dating determine glaciation timing?

A

By determining the timing of sediment burial and interpreting the depositional environment.

24
Q

What is the most common application of Optically Stimulated Luminescence dating?

A

To date the burial age of sandy sediment deposited within end moraines or in proglacial settings.

25
Q

What does Optically Stimulated Luminescence dating date?

A

It dates a mineral’s last exposure to the sun.

26
Q

What are the sampling procedures of Optically Stimulated Luminescence dating?

A

It includes obtaining sediment samples shielded from the sunlight.

27
Q

What are the largest uncertainties using Optically Stimulated Luminescence dating?

A

The unknown geologic history of the sample and whether the sample has experienced incomplete bleaching (insufficient resetting).

28
Q

How can a sample be age overestimated when using Optically Stimulated Luminescence dating?

A

Incomplete bleaching

29
Q

How can a sample be age underestimated when using the Optically Stimulated Luminescence dating method?

A

Sample contamination.

Glaciations (11 decks)

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