ESC 102- Time

Geological time scale

boundaries are between eons, eras, period

determined by events like new fossils, disappearances of fossils, major events

dating or methods to know the age of a rock

absolute age ex: 4.6 Ma

relative dating ex: older than, younger than

absolute dating- radioactive decay

regular rate for each radioactive element

measured in half lives- SET

how we get accurate dates

absolute dating- uranium/lead dating of zircons

forms in igneous rocks

extract uranium signal

very hard and resistant to weathering

decay of uranium to lead

Relative dating

fossils, cross cutting relationships

relative dating- fossil succession

occur in regular non-repeating and predictable manner

reflects sequence of bio evolution

cross cutting relaitonships

"what is cutting what"

1. C 2. B 3. A 4. D 5. E

Eons

hadean, archean, proterozoic, phanerozoic

eras

palaeozoic, mesozoic, cenozoic

periods (old to young)

cambrian ordovician silurian devonian carboniferous permian triassic jurassic cretaceous tertiary quaternary

mnemonic to remember periods

cold oysters seldom develop coloured pearls. their juices congeal too quickly

paleozoic era

explosion of life (invertebrates)

fish evolve

glaciation, low sea level

mass extinction at the end of ordovician and devonian

reefs develop

end with extinction

3 extinctions in paleozoic

ordovician, devonian, permian

Mesozoic Era

life recovered

dinosoars rule

marine and flying reptiles

no ice in the poles

first flowering plants

rocky mountains form

ends with metor extinction

cenozoic era

giant beavers, bears, mastodons, giant sloths

last wooly mammoths

first hominids

human evolution