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GEOLOGIC TIME
RELATIVE DATING
ABSOLUTE DATING AND RADIOACTIVITY
DIVISIONS OF THE TIME SCALE
RELATIVE DATING
- Law of Superposition =
Oldest rocks on the bottom, Younger rocks on the top
RELATIVE DATING
- Principle of Horizontality = Layers are generally deposited horizontally. Flat rock layers have not been disturbed
RELATIVE DATING
- Principle of Cross-cutting Relationships = A Younger feature cuts through an older feature
RELATIVE DATING
- Inclusions =
One rock unit is enclosed within another.
The rock containing the inclusions is younger than the inclusions.
RELATIVE DATING
FOSSIL SUCCESSION
Fossils = the remains or traces of prehistoric life Fossil Types Relatively recent organisms Entire animals, flesh included Petrified (turned to stone) Molds and Casts Carbonization Others (tracks, burrows, coprolites, gastroliths)
RELATIVE DATING
FOSSIL SUCCESSION
Conditions favoring preservation Rapid burial and possession of hard parts
CORRELATION OF ROCK LAYERS Matching rocks of similar age Fossils succeed one another in a definite order Index Fossils (widespread and short-lived) Fossils are environmental indicators (land or sea)
ABSOLUTE DATING
BASIC ATOMIC STRUCTURE
Protons, Neutrons and Electrons
Atomic number (# of protons)
Mass number (# of protons + # of neutrons)
Isotope (same # of p’s, different # of n’s)
ABSOLUTE DATING
RADIOACTIVITY
Spontaneous breaking apart (decay) of atomic nuclei
TYPES OF RADIOACTIVITY
Alpha Emission, Beta Emission, Electron Capture
GEOLOGIC TIME SCALE GEOLOGIC TIME SCALE
GEOLOGIC TIME SCALE
EONS = Precambrian and Phanerozoic
Precambrian Eon
ERAS = Hadean, Archaen, Proterozoic
Phanerozoic Eon
ERAS = Paleozoic, Mesozoic, Cenozoic
GEOLOGIC TIME SCALE
ERAS OF THE PHANEROZOIC ARE SPLIT
INTO PERIODS
Paleozoic Era (“ancient life”) Periods = Cambrian, Ordivician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian Mesozoic Era (“middle life”) Periods = Triassic, jurassic, Cretaceous Cenozoic Era (“recent life”) Periods = Tertiary, Quaternary
GEOLOGIC TIME SCALE
TERTIARY ANDQUATERNARY
PERIODS ARE SPLIT INTO EPOCHS
Tertiary Period (Paleocene, eocene, Oligocene, Miocene, Pliocene) EPOCHS
Quaternary Period (Holocene and Pleistocene) EPOCHS
GEOLOGIC TIME SCALE
PNEUMONICS
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