Section 1- Geological Time

Question 1

Define catastrophism

Answer 1

Geological theory from 18th century, points to disasters (floods, earthquakes)to explain features of the earths surface such as mountains and valleys

Question 2

Define uniformitarianism

Answer 2

Suggests past geological events can be explained by the forces observable today because The same geological processes happening now must have happened in the same way throughout time

Question 3

Principle of original horizontality

Answer 3

Due to gravity sedimentary rocks are deposited as horizontal layers
If sedimentary rocks are folded(or faulted) this occurred after deposition

Question 4

Principle of superposition

Answer 4

In a sequence of bedded rock, the rock above is younger than the ones below

Question 5

Igneous intrusions/cross cutting relationships

Answer 5

Igneous intrusions are younger than the rock that they intrude or break

Question 6

Principle of lateral continuity

Answer 6

Rock units with similar characteristics can be correlated across different exposures over large distances
Rocks that are similar but now separated by a valley or other feature can be assumed to be originally continuous.

Question 7

Define unconformities

Answer 7

Represent breaks in the geological record(ie. erosional surfaces and missing rock in the expected sequence)

Question 8

Principle of biotic succession

Answer 8

Since organisms have evolved and gone extinct through time, specific groups of fossils succeed one another in the rock record in a definite order, so fossil content can be used to determine the age of rock units

Question 9

2 methods of geological time

Answer 9

Relative time:
Observed contact relationships between rock units, fossil records
Absolute time: specific age of a unit in years

Question 10

Explain radiometric/absolute dating

Answer 10

Radioisotopes(parents-unstable radioactive isotope) are trapped in minerals when the crystallize and then decay through time. The ratio of parent to daughter(stable isotope resulting from decay of parent) reveals the number of half lives that have elapsed

Question 11

Geological time scale major divisions

Answer 11

Hadean Eon (4-4.5 Ga)
Archean Eon(2.5-4Ga)
Proterozoic Eon(2.5Ga-545Ma)
Phanerozoic Eon <545Ma

Question 12

Hadean Eon

Answer 12

4-4.5 Ga
Earths cooling period
Widespread volcanism

Question 13

Archean Eon

Answer 13

2.5-4Ga
First unicellular life for s(age of bacteria)
Oldest rocks found on the planet
Final stage of earths cooling and formation of the crust

Question 14

Proterozoic eon

Answer 14

2.5Ga-545Ma
Most diamonds formed
Oldest sedimentary rocks
Formation of ozone layer
First multicellular organisms(jellyfish)

Question 15

Phanerozoic Eon

Answer 15

<545 Ma
Abundant animal and plant life
Age of marine life, age of dinosaurs and age of mammals
(Paleozoic, Mesozoic,Cenozoic eras)