Transcript Superposition

The Rock and Fossil Record
Uniformitarianism
• - proposed by James Hutton
• - states that Earths landscape is
constantly changing due to the same
geologic process that have happened
throughout time (weathering, erosion,
deposition)
Catastrophism
• - states that all geologic change occurs
suddenly due to huge catastrophes
• - Now we know geologic change is a
combination of both
Relative Dating
• - to determine if something is
older or younger than something
else
Superposition
• - young rocks lie above older rocks in an
undisturbed sequence
• - however due to disturbances such as
folding, tilting, faults, intrusions, not
always in a nice horizontal layer
Superposition
Superposition
Superposition
Geologic Column
Folding
Folding
Tilting
Tilting
Faults
Faults
Intrusions
Intrusions
Geologic Column
- Geologists have combined data from all
the known undisturbed rock sequences
around the world to come up with this
• - it is the ideal sequence of rock layers that
contains all the known fossils and rock
formations on Earth, use it to interpret rock
sequences by comparing it to disturbed
rock sequence
Geologic Column
Unconformity
• - gaps in rock layer sequence
caused by erosion or
nondeposition.
Unconformity
Unconformity
FOSSILS
• - any naturally preserved
evidence of life
• - rock fossils, petrifaction, amber
fossils, mummification, frozen
fossils, fossils in tar.
Rock Fossils
Petrified Wood
Amber Fossils
Mummification
Frozen Fossils
Tar Pit Fossils
Trace Fossils
•
– preserved evidence of an
animals activity (footprints,
coprolites)
Trace Fossils
Coprolites
Mold
• – a cavity where an organism was
buried, but decayed
Mold
Cast
– when a mold gets filled in with
sediment and becomes a fossil
Cast
Absolute Dating
• – how to establish the actual age
of an object.
Radiometric Dating
– by knowing the rate of radioactive decay,
you can figure out the age of a rock.
(Uranium-lead, potassium-argon, carbon-14)
Radiometric dating
Carbon 14 Dating
Index Fossils
• – if
they know when one of the
organism lived, can date the layer
it was found in to date unknown
fossils.
Index Fossils
The Geologic Time Scale
• - divides Earths 4.6 billion year
history into distinct time intervals.
• - the divisions are eons, era,
periods and epochs.
Geologic Time Scale
Paleozoic Era – “Old Life”
• - started with no land organisms, then
came plants, amphibians and insects. At
the end came a mass extinction when 90%
of all species perished.
•
• 1. Grand Canyon formed
• 2. Trilobites in sea, land plants
• 3. Coral reefs, insects and fish
Paleozoic Era
Mesozoic Era : Middle Life”
- the age of reptiles, when dinosaurs
existed, birds and small mammals began to
evolve.
• - At the end, 50% of the species became
extinct, including dinos.
• 4. Pterosaurs appear, conifers develop
• 5. Reptiles develop
• 6. Dinosaurs abundant
Mesozoic Era
Cenozoic Era “ recent life”
• era we live in, the age of mammals, many
now extinct
• 7. Flowering plants and mammals appear
• 8. Rhinos and birds appear
• 9. Mammoths and humans appear.
•
Cenozoic Era