young
Relative time:
older than…
younger than
each layer is deposited on top of pre-existing layers
old
youngest
long period of earth history
oldest
Most recent 542 m.y.
Time is based upon fossils
Cambrian trilobite
(530 m.y.)
Devonian brachiopods and bryozoa
(490 m.y.)
Permian brachiopod
(250 m.y.)
Jurassic ammonites
(200 m.y.)
Cretaceous bivalve
(90 m.y.)
Pliocene mollusks
(3.0 m.y.)
ca. 300 Ma
250 million years of earth history
ca. 545 Ma
1.8 glaciation
Absolute time:
… millions of
years ago
65 mass extinction
210 first mammals
350 first reptiles
450 first land plants
542 first abundant fossil preservation
~3500 oldest fossils
3950 oldest rocks
0
TERTIARY
FILL IN EACH OF
THE TEN BLANKS IN
THE GEOLOGIC
TIME SCALE BELOW.
(10 points)
MISSISSIPPEAN
SILURIAN
545
PRECAMBRIAN
Names & order
of
eras
Periods
age (in m.y.) of
era boundaries
Geochronology
Radioactive atoms decay
away at a constant rate.
After 1 half-life 50% are left
After 2 half-life 25% are left
After 3 half-life 12.5% are left
After 4 half-life 6.25% are left
Ages based upon the decay of:
uranium
thorium
potassium
rubidium…
Radioactive (parent) atoms
decay away to produce
radiogenic (kid) atoms.
At: time=zero -all parent, no
kids : K/P = 0
After 1 half-life 50% parent,
50% kids :
K/P = 1
After 2 half-life 25% parent,
75% kids:
K/P=3
Geochronology
After 3 half-life 12.5% parent
87.5% kids:
K/P =7
Rock cycle
Inter-relationship between: igneous
sedimentary ROCKS
metamorphic 1.8 glaciation
Absolute time:
… millions of
years ago
65 mass extinction
210 first mammals
350 first reptiles
450 first land plants
542 first abundant fossil preservation
~3500 oldest fossils
3950 oldest rocks