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Environmental change > Dating archives > Flashcards

Dating archives Flashcards

1
Q

What are some general uncertainties of dating?

A

Human error e.g. in counting, machine accuracy, problems with the archive e.g. layers may be missing for some years etc.

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2
Q

How to trees react to climatic changes?

A

Different species react in different ways. Some get wider rings due to warming climate, others due to wetter climate etc.

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3
Q

What is annual incremental dating?

A

Working out the age of layers by having a ‘fixed’ date and counting back, e.g. if you know the top layer of an ice core is the present day you can count back from that.

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4
Q

What is tephrochronology dating?

A

Determining age by comparing ash (tephra) layers from various archives, e.g. if tephra matches other tephra from far away (gets carried by wind), and we know what eruption the other tephra belongs to, we can date the archive

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5
Q

What is U-Series dating? (Uranium-thorium dating?)

A

A radiometric dating method often used to determine the age of calcium carbonate materials e.g. coral, lake sediment

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6
Q

What could cause U-Series dating to give inaccurate results?

A

If you e.g. used U-series dating to data a lake sediment core, something such as a shell could have got washed onto the sediment which is of a different age causing it to have inaccurate results

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7
Q

What is argon-argon dating?

A

A type of radiometric dating used to date igneous rocks. As they solidify they trap Argon within them which can be used to identify their age.

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8
Q

What is a problem with argon-argon dating?

A

Weathering can cause Argon within the rock to be lost

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9
Q

What is radioactive decay?

A

When an unstable atomic nucleus emits radiation (e.g. alpha and beta particles and/or gamma rays) to form other elements (Park and Allaby, 2017).

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10
Q

What is radiometric dating?

A

Determining the absolute age of a material by measuring the decay of their radioactive elements (wiens, 2002).

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11
Q

Do stable isotopes and radioactive isotopes radioactively decay?

A

Stable isotopes don’t radioactively decay, radioactive isotopes do.

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12
Q

What is half life?

A

The time required for half a radioactive isotope/nucleus to decay.

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13
Q

What are some problems of radiometric dating?

A

Machine error, contamination from mixing samples etc.

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14
Q

Why is it often hard to date something over 50,000 years old using radiometric dating?

A

Because most of their radioactive elements will have been removed by then.

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15
Q

What does an accelerator mass spectrometer (AMS) measure? What is it measured on?

A

The decay of radiocarbon by counting the radiocarbon atoms present. It is measured on organic material e.g. shells, bones, wood etc.

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16
Q

What is absolute dating?

A

Using a range of methods to determine the certain/absolute age of an object or material e.g. by using radiometric dating (Park and Allaby, 2017).

17
Q

What is relative dating?

A

Determining the relative age of materials and order of past events based on their position within layers of e.g. rocks (Darvill, 2009).

18
Q

How are annual increments used in dating? What is an example of an annual increment?

A

Tree rings are annual increments. They can provide absolute ages if you have one or more point that is absolute.

19
Q

What is age equivalence dating?

A

Knowing that a point in one archive is the same as a point in another archive and using this to date it.

20
Q

Name the four broad categories of dating

A

Absolute dating, relative dating, annual increments, age equivalence.

21
Q

What does dating method choice depend on?

A

How far back in time you want to go and the material content.

22
Q

What does dating archives involve?

A

Working out how old each section of the archive is, then using the proxies within them to determine when climatic changes occurred.

23
Q

Proxies taken from e.g. the top of a peat or ice core represent what?

A

Present day climate.

24
Q

What are cosmogenic nuclides?

A

Nuclides that form in rocks on the surface due to large exposure to high energy cosmic waves (Davis, 2014)

25
Q

What is cosmogenic nuclide dating?

A

Using interactions between cosmic rays and nuclides to determine how long something has been exposed to the surface, NOT how old it is (Davies, 2014)

Environmental change (19 decks)

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