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29.3 A BSOLUTE T IME. H ISTORICAL M ETHODS Counting rigs in trees – more accurate, but cannot calculate very old material.

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Presentation on theme: "29.3 A BSOLUTE T IME. H ISTORICAL M ETHODS Counting rigs in trees – more accurate, but cannot calculate very old material."— Presentation transcript:

1 29.3 A BSOLUTE T IME

2 H ISTORICAL M ETHODS Counting rigs in trees – more accurate, but cannot calculate very old material.

3 H ISTORICAL M ETHODS Estimating rates of erosion and sedimentation – Only useful for younger geologic features.

4 H ISTORICAL M ETHODS Counting Varves – The sediments that form in bodies of water annually. (Optional) Ex. The glacial lakes deposit a like thin layer in the summer and a dark layer in the winter.

5 R ADIOACTIVITY Radioactive Decay – the process of an atomic nucleus losses E by emitting ionizing particles and radiation. (Alpha, Beta & e- capture)

6 R ADIOACTIVITY Radioactive Decay Alpha Decay : An alpha particle (2 e+ and 2 e-) are emitted.

7 R ADIOACTIVITY Radioactive Decay Beta Decay: A neutron disintegrates into a e+ and a e- (beta particle)

8 R ADIOACTIVITY Radioactive Decay e- capture: A e+ captures an e- and becomes a neutron.

9 R ADIOACTIVITY Radioactive Decay As decay continues the atom becomes an isotope of a different element. Continues until it becomes a stable (non radioactive isotope).

10 R ADIOACTIVITY Radioactive Decay Parent Isotope – Original element/atom Daughter Isotope – product of the original. Ex. C14->N14

11 H ALF L IFE The time it takes half an atoms radioactive material to decay to a stable product. U 238 has a half life of 4.5 b.y.

12 R ADIOMETRIC D ATING Radiometric Dating The process of measuring the amount of parent and daughter material and using the ratio to find the age of the material. (Rocks, minerals and organic material)

13 R ADIOMETRIC D ATING Radiocarbon Dating Using C12 and C14 to date dead organisms. (not useful for organisms older than 70,000 y.o.)

14 R ADIOMETRIC D ATING Radiometric Dating U-Pb Dating: Used to date rocks that contain U and Pb. Not acurate for rocks less than 10 myo.

15 R ADIOMETRIC D ATING Radiometric Dating Rubidium/Strontiu m dating, Used to date rocks that contain Rb and Sr. Used for extremely old rocks.

16 R ADIOMETRIC D ATING Radiometric Dating Potassium/Argon dating, Used to date rocks that contain K and Ar. Can be used to date rocks as young as y.o. Met/Sed/Ig Rocks


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