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Absolute Dating
Relative Dating
Vocabulary
Absolute Dating (solve)
100

The process used to determine a precise age of fossils and rock

What is absolute dating?

100
Dating rocks and events based upon other rocks and events
What is relative dating
100

A surface where rock layers were first eroded away, then new deposition was placed over this surface. It represents a gap in the rock record.

What is an unconformity?

100

A sample was taken from a fossil and it was found that 50% of the fossil contains Carbon-14 (half-life of 5,750). How old is the fossil?

What is 5,750 years old

200

The unstable elements found in fossils

What are radioactive isotopes?

200
The rocks on the bottom are older and the rocks on the top are younger
What is the Law of Superposition
200

A special type of fossil that was widely distributed, common, and lived for only a short period of time.

What is an index fossil?

200

A sample of wood found in an ancient tomb contains 25% of its original carbon-14. The age of this wood sample is approximately _______________.

 (half-life of 5,750 years)

What is 11, 500 years old? (5,750 X 2 half lives)

300
Process that occurs when the parent isotope (radioactive) decays into a daughter isotope (no longer radioactive)
What is radioactive decay?
300

This principle of relative age dating states that layers of sediment are originally deposited in flat, horizontal sheets. Even if layers tilt due to uplift, they were originally flat

What is the Law of Original Horizontality?

300

This type of unconformity is where sedimentary layers are deposited on top of older, horizontal sedimentary layers that were eroded.

What is a disconformity?

300

A radioactive isotope under goes a half life every 22 years. This much of the original isotope would remain in a 20 gram sample after 66 years.

What is 2.5 grams? (3 half lives; 1st-10g, 2nd-5g, 3rd-2.5g)

400
The time it takes for half the atoms in a sample to change from a radioactive isotope to a new stable atom
What is a half life?
400

This principal states that sediment is deposited in a continuous sheet until the amount thins out or hits a barrier.

What is the Law of Lateral Continuity?

400
The remains or impression of a once-living organism preserved in rock or other material.
What is a fossil
400

You start with 200 g of radioactive isotope Y. If isotope Y has a half life of 14 years, it would take ________ years to decay and be left with only 25 g of material.

What is 42 years? (200->100->50->25; 3 half lives. 3 x 14 = 42).

500

This elemental isotope is only used to date matter that was once living. The amount of this radioactive element begins to decrease the moment the organism dies, so any age determined with this isotope is from when the fossil died.

What is Carbon-14

500

In this picture, it is the youngest feature of these rock layers.

What is the Fault?

500

Magma pushes through sedimentary layers, eventually crystallizing into this type of rock, forming a dike.

What is igneous rock?

500

A sample of carbon-14 under goes 3 half lives. This percentage of the sample has decayed into a stable daughter isotope?

What is 87.5%