Geomorphology 4

Question 1

What drives plate movement

Answer 1

Internal heat, drives convection to form new crust

Question 2

Divergent plate boundaries

Answer 2

Rising magma cools forming new oceanic crust

Basalt and gabbro composition, fine crystals (rapid cooling)

Ocean crust density 3.0 g/cm3

Question 3

Convergent plate boundaries

Answer 3

Subducting ocean crust and partial melting
=lower density 2.7 g/cm3

Magma rises firm igneous rocks - granites

Question 4

Oceanic crust gets what as it spreads from core

Answer 4

Older colder denser

Question 5

How often are:

• Super continents
• Main collision zones/Continents

Reorganised?

Answer 5

200ma

3-500 Ma

Question 6

Implications for crustal elevation

Answer 6

Cool materials are denser, colder oceanic crust sags into mantle to form the trench

Pull-force exerted by descending plate

Continental crust too buoyant to be subduction

Compressive strength = deform and thickening

Question 7

What is isostasy

Answer 7

State of equilibrium where crust floats at an elevation determined by its thickness and density

Question 8

how big is the crust for a 3km mountain

Answer 8

75 Km

Thickness value and hidden value

Question 9

Surface uplift is only what percentage of crustal uplift?

Answer 9

1/6 th

Question 10

Implications for elevation distributions

Answer 10

Distribution is Vinod all reflecting differing densities

Extreme elevations reflect convergence and subduction

Thickest crust at continent continent convergence or ocean continent

Question 11

Craton

Answer 11

2bn + year bedrock

Old cold and stable

Continents form and reform around them

Question 12

Shield

Answer 12

Exposed craton

Question 13

Platform

Answer 13

Craton covered by sedimentary rock

Question 14

Basins

Answer 14

Intracontinental basins subside due to:

Thinning, cooling of crust and loading with sediments

Subside adjacent to mountain chains caused by crustal thickening

Question 15

Rift zones

Answer 15

Extended crust

Thermal buoyancy - rift mountains , lithospheric extensions produce rift basins and valleys

Question 16

What are orogens

Answer 16

High elevation zones of plate convergence

Question 17

Examples of orogens

Answer 17

Andean - continent ocean VOLCANISM

Himalayan - continent continent

Question 18

How does crustal shortening happen in orogenies

Answer 18

By folding and faulting

Continents become sutured together by folding and faulting (thrust faults)

Question 19

driving energy of surface processs

Answer 19

Internal Geothermal energy - drives endogenous processes that are constructional, generate relief

External solar energy - exogenic processes, denudation, chemical and physical weathering

Potential energy - drivers of exogenic processes

Question 20

How else can mountains be elevated

Not collision

Answer 20

By incisions

Eroded volume causes change in equilibrium and therefore can rise in elevation as there it is less dense

Question 21

What is earths crust determined by

Answer 21

Crustal composition, thickness, temperature

Question 22

How is topography created

Answer 22

By endogenic processes

But form and evolution of topography reflects relationship competition between endogenic and exogenic forces

Question 23

Grotzinger

Answer 23

2014

Wilson cycle

Plate tectonics and mountain building

Question 24

Anderson

Answer 24

2010

Question 25

2010

Answer 25

Anderson

Tectonic geomorphology revitalised by new techniques for deterring the ages and rate of geomorphic processes

Now possible to monitor movement at scales if mm and can also quantify how rapidly rivers and glaciers incise bedrocks/ erode

Merger of data sets = new understanding of balance between rates at which crustal material is added and rates of erosion