Lecture 4 - Geology

Question 1

rock types

igneous

Answer 1

cooling of magma, contains datable minerals

Question 2

rock types

sedimentary

Answer 2

accumulation of particles

Question 3

rock types

clastic

sedimentary

Answer 3

particles are weathered bits of other fossils
- sandstone, conglomerate, breccia

Question 4

rock types

organic

sedminetary

Answer 4

particles are animal/plant debris (CaCO3 etc), especially in shallow water

Question 5

rock types

creation of sedimentary rock

Answer 5

filling of low lying areas (basins); action and speed of water flow is key - determines size/density of particles deposited

Question 6

rock types

chemical

sedimentary

Answer 6

particles are dissolved minerals that precipitate directly from suspension

Question 7

fossils

fossil definition

Answer 7

mineralized remains of an organism, or impression of the organism
in terrestrial settings, usually occurs in clastic sedimentary rock

Question 8

fossils

process of fossilization

Answer 8

death, neglect, burial, fossilization

Question 9

stratigraphy

strate

Answer 9

layers of rocks

Question 10

stratigraphy

principle of original horizontality

Answer 10

strate are layed down horizontally originally, any tilt happens after they are laid down

Question 11

stratigraphy

principle of lateral continuity

Answer 11

chemically identical beds are part of the same layer of rock bed, even if later moved on

Question 12

stratigraphy

law of superposition

Answer 12

older layers at the bottom, younger on top

Question 13

stratigraphy

principle of cross-cutting

Answer 13

cross-cutting layers can only cut existing layers, so it is younger than those it cut

Question 14

stratigraphy

principle of faunal succession

Answer 14

use biological organisms present in fossil bed to determine age of strate

Question 15

stratigraphy

index fossils

Answer 15

organisms that are more specific to a certain time period/relatively constrained times - more indicative of the age of strata

Question 16

absolute dating methods

14C dating

Answer 16

estimate age based on proportion of remaining 14C
- half-life = 5730 years
- becomes negligible after 50k years

Question 17

absolute dating methods

K-Ar Dating

Answer 17

decay of 40K to 40 Ar
- Ar gas escapes liquid magma, but accumulates as magma and hardens (Ar “zeroed” out at eruption)
- half-life = 1.3 billion years

Question 18

absolute dating methods

tephra

Answer 18

bed formed by volcanic ashfall
contains glass & minerals that can be directly dated

Question 19

absolute dating methods

magnetostratigraphy

Answer 19

earth’s core is magnetic, measure of mineral alignment to understand magnetic field = placement of time