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39 Cards in this Set
- Front
- Back
Radiometric dating
|
determine ratio of parent
nuclei to daughter nuclei (in a fossil or a rock). |
|
Half-life
|
time it takes 1/2 of original
amount to decay. |
|
Dendrochronolgy
|
science of comparing
annual growth rings in trees to date events & change in past environments. |
|
Varves
|
accumulate in water, made
of sediments. |
|
Keybed
|
distinctive layer that acts as
a time marker. |
|
Unconformity
|
gap in rock layers--due to
erosion. |
|
Angular unconformity
|
layers deposited; later
tilted/folded; new horizontal layers deposited. |
|
Correlate
|
match up layers of rock over
gr8 distances. |
|
Principle of
Uniformitarianism |
~the present is key to the past
~processes occuring today have been occuring since the earth formed |
|
Relative Age Dating
|
place ages of rocks & events
that formed them in order but w/out exact dates. |
|
Principles:
|
1. Original Horizontality
2. Superposition 3. Cross-Cutting 4. Unconformity |
|
Original Horizontality
|
sedimentary rocks are
deposited in horizontal layers. |
|
Superposition
|
in an undisturbed rock
sequence, oldest are on bottom, & ea. successive layer is younger than layer beneath. |
|
Cross-Cutting
|
an igneous intrusion or a fault
is younger than the rock it cuts across. |
|
Fossils
|
evidence/remains of once
living plants or animals. |
|
Formation of Fossils:
|
~quick burial
~presence of hard prts. |
|
Original Preservation
|
frozen; tar pits; insects
trapped in amber. |
|
Perminerialization
|
organic matter removed;
replaced w/ minerals; petrified wood, bone. |
|
Molds
|
cavity left in a rock when
organism's prts in a rock are weathered & eroded. |
|
Cast
|
produced when a mold is
filled w/ sediments & hardens into a rock. |
|
Trace Fossils
|
hand/foot prints
(not body parts) |
|
Evolution
|
1 piece of support of fossils.
|
|
Epochs
|
smallest; m.y. to 10's m.y.
|
|
Eon
|
largest; longest unit by
(Phanerozoic) |
|
Era
|
100's of m.y. to b.y.
(m.y. : millions of yrs.) (b.y. : billions of yrs.) |
|
Period
|
10's m.y. to 100's m.y.
(life forms found in fossil record) |
|
Erosion
|
A common cause of gaps in
rock layers. |
|
Fossils
|
evidence/remains of once living plants or animals.
|
|
Formation of Fossils:
|
~quick burial
~presence of hard prts |
|
original preservation
|
frozen; tar pits; insects trapped
in amber |
|
Permineralization
|
organic matter removed;
replaced w/ minerals; petrified wood, bone. |
|
Molds
|
cavity left in a rock when
organism's prts in a rock are weathered & eroded. |
|
Cast
|
produced when a mold is filled w/ sediments & hardens into a rock.
|
|
Trace Fossils
|
hand/foot prints---
(not body parts). |
|
Evolution
|
change; 1 piece of support
of fossils. |
|
Epochs
|
smallest; m.y. to 10's m.y.
|
|
Eon
|
largest; longest unit b.y.
(Phanerozoic) |
|
Era
|
100's m.y. to b.y.
|
|
Period
|
10's m.y. to 100's m.y.; life forms found in fossil record.
|