lecture 3 -global geomorphology and tectonics

Question 1

define hypsometry

Answer 1

the measurement of land elevation relative to sea level

Question 2

define bathymetry

Answer 2

the underwater equivalent to hypsometry / measurement of land elevation below sea level

Question 3

earth’s hypsometry is bimodal due to…

Answer 3

thickness and density of crust

Question 4

define isostasy

Answer 4

the state of equilibrium such that the earth’s lithosphere floats at an elevation determined by their thickness and density

Question 5

what are the controls of elevation?

Answer 5

1. creation of continental and oceanic crusts
2. mountain range / continental collision (thickening)
3. geomorphological processes cut valleys, sculpting individual mountains

Question 6

define rifting

Answer 6

formation of fissures / breaks, through large scale faulting; moving apart

Question 7

what is the Wilson cycle?

Answer 7

the cyclical opening and closing of ocean basins caused by movement of the earth’s plates

Question 8

what is the supercontinent cycle?

Answer 8

aggregation and dispersal of earth’s continental crust

Question 9

oceanic crust:

Answer 9

• young (200 ma)
• constantly recycled
• not complex

Question 10

continental crust:

Answer 10

• recycled less

- modified and survive through deep time

Question 11

what is a craton?

Answer 11

very old (3 billion years) stable parts of crust
affected little by plate tectonics - continents form and reform around them

Question 12

what is a shield?

Answer 12

an exposed craton

Question 13

what is a platform?

Answer 13

craton covered by sedimentary rock

Question 14

what is an orogen?

Answer 14

younger, mountain building parts of the crust

Question 15

convergent margins produce…?

Answer 15

island arcs
continent - margin orogens
collisional orogens

Question 16

what is a passive margin?

Answer 16

an ancient rift flank no longer tectonically active, uplift caused by flexure and erosion

Question 17

topography reflects competition between the effects of which 2 energy sources?

Answer 17

internal (endogenic) and external (exogenic)

Question 18

define endogenic

Answer 18

occur beneath the surface of the earth e.g. convection for plate tectonic movement

Question 19

define denudation

Answer 19

processes that wear away the earth’s surface e.g. chemical and physical erosion

Question 20

what is a nappe?

Answer 20

large body / sheet of rock that has been moved a distance of 2km or more from its original position by thrusting or folding

Question 21

define shortening

Answer 21

the thickening of the crust achieved by faulting and folding

occurs in continent - continent collisions / convergent margins where no subduction occurs

Question 22

what controls height?

Answer 22

1. tectonics: rate of shortening, isostasy, topography
2. denudation (lowering by erosion): influenced by slope, rock strength, climate
   * the competition between tectonic vs surface processes