Geological Time Scale

Question 1

Uniformitarianism

Answer 1

James Hutton-1785
“present is the key to the past”
-physical processes that operate in the modern world also operated in the past at roughly the same rates.
-These processes were responsible for forming geological features preserved.

Question 2

Label the 3 types of Unconformities

Answer 2

1.) Angular
2.) Nonconformity
3.) Disconformity

Question 3

Angular Disconformity

Answer 3

A discrete change in the tilt of rocks across an erosional surface

Question 4

Nonconformity

Answer 4

Eroded igneous or metamorphic rocks, overlain by a younger rock unit

Question 5

Disconformity

Answer 5

An erosional surface w/ no change in tilt across it; missing rock layer

Question 6

The Phanerozoic Eon

Answer 6

541 Ma-Present
1.) Paleozoic “age of fishes” -ancient life (541ma -252ma)
2.) Mesozoic “age of dinos”- middle-life (252ma-66ma)
3.) Cenozoic “age of mammals”-recent-life (66ma-present)

Question 7

How are divisions of the geological time scale defined in Phanerozoic?

Answer 7

-Age of visible life; so divisions are based on appearance/disappearance of diff species

Question 8

(T/F): Mammals 1st appeared after dinos went extinct

Answer 8

False

Question 9

Precambrian

Answer 9

Early:
-Moon impact
-Oldest preserved minerals ~liquid water/oceans
-First Evidence of life
Middle:
-Evolution of early life (simple single cell; prokaryotes-> multi-celled organisms; eukaryotes-> single cells with fibers for mobility)
-Great Oxidation Event (~2.4 Ga)
Oxygen generated by photosynthetic organisms (cyanobacteria) building oxygen in the atmosphere
Late:
-1st complex macroscopic organisms

Question 10

The Permian-Triassic Mass Extinction

Answer 10

Largest extinction in earths history
*90% of marine extinct
*70% of terrestrial extinct
-occurred from eruption of Siberian Traps flood basalts. (6000 km^3 of erupted lava)
-Intrusion of magma into organic-rich shale and petroleum bearing rocks led to release of greenhouse gases
Kill mechs:
1.) Global Warming (~8 °C)
2.) Ozone Depletion
3.) Acid Rain
-Marks the end of Paleozoic

Question 11

Paleozoic

Answer 11

Ancient -Life: “Age of Fishes”
-Invasion of Land: 1st plant fossils on lant
-Final assembly of Pangea
-pre-mammal and Early reptiles reproduce on land
-Siberian Traps led to Permian-Triassic Mass extinction=end of Paleozoic period

Question 12

Mesozoic

Answer 12

Middle-Life : “Age of Dinos”
*birds are dinos
-Dinos become dominant species after surviving Triassic mass extinction
Asteroid event takes out Dinos and marks end of Mesozoic
-K-Pg boundary used as evidence for meteor asteroid event

Question 13

K-Pg Boundary-Iridium Anomaly

Answer 13

Unusual abundance of iridium in layer of rock strata (K-Pg)
-Iridium is a rare, heavy metal. Heaviest metals come from super nova events. So iridium’s presence is used as evidence of meteor strike to explain mass extinction of the dinosaurs.

M11 Earthquakes, tsunamis, thermal radiation, and acid rain.
Long-term impact: cooling dur to soot and sulfur aerosols (-10 °C for years-decades)

Question 14

Cenozoic

Answer 14

diversification of most modern mammals
-human evolution