THE
WAY THE EARTH WORKS
GEOLOGIC TIME
I.
Introduction
A.
Importance
B.
Terminology
1.
Relative time (Principle of Superposition, cross-cutting relations,
paleontology)
2.
Absolute time (isotopic age determinations using different isotopic decay
schemes)
3.
Duration of specific events
B.
Brief review of approaches
"How
between the various layers of stone are still to be found the tracks of worms
which crawled about upon them when it was not yet dry. How all the marine clays contain shells, and
the shell is petrified together with the clay.
Of the stupidity and ignorance of those who imagine that these creatures
were carried by the Deluge to such places distant from the sea........ And if the
above-mentioned Deluge had carried them to these places from the sea, you would
find the shells at the edge of one layer of rock, not at the edge of many,
where may be counted the winters of the years during which the sea multiplied
the layers of sand and mud brought down by the neighboring rivers and spread
them over its shores. And if you should
wish to say that there must have been many deluges in order to produce these
layers and the shells among them, it would then become necessary for you to
affirm that such a deluge took place every year. "
Folio
10r, Codex Leicester, Leonardo da Vinci, 1508.
C.
Estimates of the Age of the Earth
II.
Unconformities
A.
Definition
B.
Angular
C.
Nonconformity
D.
Disconformity
III.
Relative Time (using specific areas as examples)
A.
Principle of Superposition
B.
Cross-cutting relations
1.
igneous rocks
2.
faults
Stratigraphic
Correlations
IV.
Geologic Time Scale
A.
Established on the basis of the Stratigraphic Record
B.
Components (Subdivisions) of the Time Scale
1.
Eons
2.
Eras (erathem)
3.
Periods (system)
4.
Epochs (series)
[5.
stages]
C.
Geomagnetic polarity time scale
D.
How are Absolute Ages tied to the Time Scale
V.
Absolute Ages of Specific Geologic Events
A.
Last geomagnetic field reversal
B.
Cretaceous/Tertiary Boundary
C.
Precambrian/Cambrian Boundary