TIME AND TECTONICS IN GEOSPHERE

Question 1

when was the geologic time scale developed?

Answer 1

1800

Question 2

when was radioactivity discovered and its definition

Answer 2

• 20th century
• measurment of geologic time

Question 3

description and principle

stratigraphy

Answer 3

• relative age dating for sedimentary rock
• 18th century basic principles from observing layers of sedimentary rock
  1. correlation
  2. order of strata
  3. cross cutting

Question 4

correlation by lithology

Answer 4

• comparing sucessions of layers in different places

Question 5

description and example, a date

correlation by fossils

Answer 5

• correlating strata based on fossils
• its characteristics are adundancy, a wide distribution, marine and rapid evolution
  *abundant in paleozoic

Question 6

description and example

cross cutting relationships

Answer 6

• events that modify rocks after deposition
• show relative age of features
• examples are uncomformities, faults, igneous intrusions

Question 7

dykes and inrusions are..

Answer 7

are younger than the host rocks

Question 8

precambrian division of eons

Answer 8

protozeroic, archean, hadean

Question 9

how is the phanerzoic eon divided

Answer 9

• fossil investigations
• superposition
• cross cutting

Question 10

order of strata

Answer 10

• sedimentary rocks thatrecord environmental change

Question 11

the sucession of sedimentary layers is illustrated in..

Answer 11

stratigraphic columns

Question 12

absolute time method

Answer 12

isotopic dating

Question 13

isotopic dating -neurons

Answer 13

• neurons play a role in binding the nuckeus together
• the number of neutrons can vary- it defines

Question 14

radioactive decay

Answer 14

*unstable isotopes decay to create stable isotopes
* so nucleus breaks apart and undergoes decay, and creates a new element randomly
* the rate is predictable
* used for measurement of geologic time

Question 15

radioactive decy-

half life

Answer 15

the time for half the atoms of an isotope to decay
* after 2 half lives, a quarter of atoms are left

Question 16

radioactive decay-

daughter atoms

Answer 16

• the new element of the decay

Question 17

requirements of age determination

Answer 17

• half life or decay constant
• final amount of parent isotope
• og amount of parent isotope or final amount of daughter isotope

Question 18

when did the great oxygenation event occur

Answer 18

2.45 ga - 2.2 ga

Question 19

when was the emergence of photosynthesis

Answer 19

1.25 ga

Question 20

oceanic crust make up

Answer 20

• mafic igneous rock
• basalt

Question 21

continental crust

Answer 21

• igneous, sedimentary, metamorphic
• intermediate - felsic composition

Question 22

hypotheis date

contental drift date

Answer 22

1914

Question 23

gravity and the asthenosphere

Answer 23

• stronger attraction to denser rocks close to the surface
• measure of gravity is all objects attract each other according to mass
  *

Question 24

what started the theory

theory of isotasy

Answer 24

• mtns are underlain by lighter rocks / asthenosphere

Question 25

asthenosphere

Answer 25

* The layer of the mantle lying beneath the lithosphere and capable of plastic flow * can allow plate movement to occur

Question 26

lithosphere

Answer 26

* division of plates above the asthenosphere\ * undergoes vertical isostatic rebound after ice melts

Question 27

dipole field

Answer 27

The magnetic field produced by a magnetized body with north and south poles on opposite sides

Question 28

magnetism

Answer 28

* the magnetic core of earth suggests it is circulating liquid iron *

Question 29

declination

Answer 29

* The direction relative to the north of Earth’s magnetic field. * indicates direction to the pole

Question 30

inclination

Answer 30

The steepness of Earth’s magnetic field/ of the declination * indicates distance from the pole

Question 31

paleomagnetism

Answer 31

* The study of preserved magnetism in ancient rocks * when magnetite cools it is magnetized by the surrounding megnetic by the earths field

Question 32

remnant magnetism

Answer 32

* magnetite rocks form and make a record of the earth magnetic field as it existed at the time of their formation, so * RM determines the ancient location of the N or S pole relative to rocks as currently found

Question 33

MAGNETIC REVERSALS

Answer 33

reversal of N and S poles recorded by remnant magnetism

Question 34

MAGNETIC ANOMOLY

Answer 34

field slightly stronger or weaker than normal * result from remnant magnetism acquired during spreading of ocean floor while magnetic reversals occured * determines age of ocean floor