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Week 3 - Dating Archives Flashcards

(17 cards)

1
Q

What are 3 types of dating?

A

Absolute dating

Annual increments

Age equivalence

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2
Q

What is annual dating?

A

Provides an absolute age (with uncertainties). Eg this sample is 8000 years plus or minus 250 years

Radiocarbon dating

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3
Q

What is annual increments dating?

A

Can provide absolute ages if you can fix one or more points with an absolute date or the present. Eg the outside of a tree is the fixed point because it is present day, then counting tree rings provides age

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4
Q

What is age equivalence dating?

A

Knowing that a point in one archive is the same age as a point in another.

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5
Q

What is radioactive decay?

A

Radioactive isotopes decay to form other elements

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6
Q

How do you find out the age of a parent radioactive isotope?

A

By measuring the number of half lifes

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7
Q

The half life of carbon-14 is ___ years

A

5730

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8
Q

What tool measures the decay of radiocarbon (carbon-14)?

A

An accelerator mass spectrometer (AMS)

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9
Q

A sample that contains little 14C will indicate…

A

That the sample is old

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10
Q

How far back can carbon 14 be dated back to?

A

50,000 years BP

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11
Q

In a lake, what is the difference between Uranium and Thorium?

A

U is more soluble than Th

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12
Q

Why might Th not be present in present day lake waters but present in old lake sediments?

A

Because U decays in Th, the more Th there is the older the sediment

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13
Q

In lake’s, where does Uranium come from?

A

Precipitated with calcium and incorporated into carbonate crystals

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14
Q

How are cosmogenic nuclides formed?

A

From bombardment of cosmic rays that hit the surface rocks

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15
Q

The more cosmogenic nuclides that rocks contain, the longer it has been ____ at the surface

A

Exposed

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16
Q

How far back can cosmogenic nuclides be dated?

A

Millions of years

17
Q

What happens to the content of cosmogenic nuclides when a rock is exposed, buried, then exposed again?

A

Erodes away cosmogenic nuclides from the first exposure. But sometimes doesn’t get rid of all original cosmogenic nuclides