GEO 303 Chapter Notes - Chapter 11: Sedimentary Rock, Erosion Surface, Radiogenic Nuclide
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10 May 2016
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Geo Notes Chapter 11:
The Discovery of Time
oEarly Speculations
Philosophers?
oThe Rule of Authority
The Bible (what the fuck is this textbook)
oAdvent of the Scientific Method
History isn’t endless repetition, its an evolutionary
development in which the achievements of each new era were
based on upon those inherited from the previous era
Unconformity: the buried erosion surface that separates the
older and younger series of beds, represents the period of time
during which a part of previously deposited geologic record
was destroyed
Uniformitarianism: emphasize the continued application of
uniform processes
oToward a Geologic Clock
Hour glasses
oUsing Radioactivity to tell time
Radioactive: unstable isotopes
Nuclear stability
Determined by competition between opposing factors,
an immensely powerful nuclear force binds the protons
and neutrons together, but the energy contained in the
nucleus tends to disrupt it
Some of this internal energy is released through the
processes of radioactive decay
In most cases, a particle with mass is also expelled from
the nucleus causing it to transform into an isotope of
another element
oWe say that a radioactive or parent atom has
decayed into a radiogenic or daughter atom
oDaughter will keep decaying if its radioactive
until stability is reached
Radioactive decay is a statistical process, which means
we can predict only the average behavior of a large
population of atoms
oHalf life: length of time required for one-half of
an initial number of radioactive atoms to decay
oIsotopic Ages
Half-life reduces by half every half life (1, ½, 1/4, 1/8)
Radioactive counter: device that measures decay events atom
by atom
oMass Spectrometers
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