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21 Cards in this Set

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Bishop Ussher
used the bible to date the earth, said that it was about 6000 years old
Catastrophism
belief that worldwide events happened to create the earth, earth was 6000 years old, except that radioactive dating is wrong
James Hutton
observed sedimentation rates, said that the earth was older than 6000 years old
Uniformitarianism
process of the earth still happening today, except that it was slower now, no specific number of how old the earth is
William Thompson
assumed earth had been cooling steadily since made, called for 20 million year old earth
John Joly
assumed oceans had collected salts from erosion at a constant rate, calls for 90 million year old earth
the Curies
discovered radioactive dating, and estimates the earth to be 4.6 billion years old
Absolute Dating
gives an actual number, cant be used on all rocks, dependent on interactions of strong and weak nuclear forces
Radioactive decay
when a parent gives off an alpha particle (2 pro, 2 neut) from its nucleus and transforms to an entirely different element, comes at a very predicable rate
one half life
1:1
two half lives
1:3
three half lives
1:7
four half lives
1:15
five half lives
1:31
six half lives
1:63
1/8 of a half life
15:1
1/4 of a half life
7:1
1/2 of a half life
3:1
Relative Dating
gives ages only to relation to others
Law of Superposition
says that the sediment on the bottom is older than the sediment on the top
Index fossils
must be widesperad, short lived, easily fossilized and have bones