29.3 a bsolute t ime. h istorical m ethods counting rigs in trees – more accurate, but cannot...
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29.3 ABSOLUTE TIME
HISTORICAL METHODS
Counting rigs in trees – more accurate, but cannot calculate very old material.
HISTORICAL METHODS
Estimating rates of erosion and sedimentation – Only useful for younger geologic features.
HISTORICAL METHODS
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.
RADIOACTIVITY
Radioactive Decay – the process of an atomic nucleus losses E by emitting ionizing particles and radiation.
(Alpha, Beta & e- capture)
RADIOACTIVITY
Radioactive Decay Alpha Decay : An
alpha particle (2 e+ and 2 e-) are emitted.
RADIOACTIVITY
Radioactive Decay Beta Decay: A
neutron disintegrates into a e+ and a e- (beta particle)
RADIOACTIVITY
Radioactive Decay e- capture: A e+
captures an e- and becomes a neutron.
RADIOACTIVITY
Radioactive DecayAs decay continues
the atom becomes an isotope of a different element. Continues until it becomes a stable (non radioactive isotope).
RADIOACTIVITY
Radioactive Decay Parent Isotope –
Original element/atom
Daughter Isotope – product of the original.
Ex. C14->N14
HALF LIFE
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.
RADIOMETRIC DATING
Radiometric DatingThe 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)
RADIOMETRIC DATING
Radiocarbon Dating Using C12 and
C14 to date dead organisms. (not useful for organisms older than 70,000 y.o.)
RADIOMETRIC DATING
Radiometric Dating U-Pb Dating: Used
to date rocks that contain U and Pb. Not acurate for rocks less than 10 myo.
RADIOMETRIC DATING
Radiometric Dating Rubidium/
Strontium dating, Used to date rocks that contain Rb and Sr. Used for extremely old rocks.
RADIOMETRIC DATING
Radiometric Dating Potassium/Argon
dating, Used to date rocks that contain K and Ar. Can be used to date rocks as young as 50000 y.o. Met/Sed/Ig Rocks