Transcript GeologicTimePPT

James Hutton
Uniformitarianism:
the processes that
act on the Earth’s
surface today are
the same as the
processes that
have acted on the
Earth’s surface in
the past
“The present is the key to the past”
age of anything
compared to the
age of something
else
•doesn’t indicate actual
date of occurrence
law of superposition: in
undisturbed rock, the older
rocks will be at the bottom
and the youngest rocks will
be at the top
law of cross-cutting
relationships:an igneous rock
cutting through another rock
is younger than the rock it
has cut-cross
law of included fragments:
pieces of one rock found in
another rock must be older
than the rock in which they
are found
unconformity:
break in
the
geologic
rock
record
Contorted rock, hard to determine relative age (Copiapo, Chile)
•nonconformity: when
stratified rock rests upon
unstratified rock
Noncomformity
1. Granite formed
2. Granite exposed by erosion
3. Beds 1-3 deposited
•angular unconformity:
boundary between horizontal
and tilted layers of rock
Angular Unconformity
1. Beds 1-6 deposited
2. Beds 1-6 tilted
3. Erosion
4. Beds 9,10 deposited
•disconformity:boundary
between layers of rock that
have not been deposited
continuously
Disconformity
1. Beds 1,2 deposited
2. Erosion
3. Beds 5, 6, 7 deposited
absolute age: identifies
actual age of a rock layer
•if actual time of two events
is known, the length of time
between two events can be
calculated
fossil: remains or evidence of
living things
(1) original remains: the actual,
unchanged remains of the
organism are preserved
(a) frozen in ice
(b) preserved in amber(tree
sap that has hardened
(c) mummification
(2) replaced remains: soft
parts of the organism have
disappeared and been replaced
by minerals
petrification
(3) molds and casts of the
original organism
(4) trace fossils: evidence of
life other than remains of an
organisms activities and/or
appearance
(a) footprints
(c) tracks, trails,
burrows, borings
(b) imprint
coprolites: fossilized dung or
waste materials from ancient
animals
T-Rex Carnivore Coprolite (8 lbs.)
gastroliths: fossilized stone
found within the digestive
system of a dinosaur or other
reptile
index fossil: fossils found
exclusively in rock record of a
particular geologic age
•must have (4) characteristics:
(1) must be easily recognizable
(2) must be widespread in occurrence
(3) must be limited in time
(4) must be found in large numbers with
the rock layer
geologic time scale: summary of
major events of the Earth’s
history preserved in the rock
record
•the history of the Earth is
divided by major changes in the
Earth’s surface, climate and/or
species
Eras: largest segment of time
(1) Precambrian
(2) Paleozoic- “ancient life”
(3) Mesozoic- “middle life”
(4) Cenozoic- “recent life”
Eras are divided into Periods,
Periods are divided into Epochs
theory of
evolution: theory
that organisms
change over time
and new organisms
are derived from
ancestral types
•theory proposed
by Charles Darwin