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.

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Cenozoic Era