L2, Mass Wasting

Question 1

produce soil

Answer 1

Continuous insidious retreat in humid/vegetated areas

Question 2

Weathering by Biota

Answer 2

if no sediment and water → soil

sediment interactions with vegetation, animals and microbes, will tell you this is a terrestial environment

Question 3

soil layer

Answer 3

process operates from top down
bare top soil easily removed (ex. dust bowl)
zone of leaching and zone of accumilation
topsoil: where vegetation grows
subsoil , bare rock
vegetation cover stabilises the surface but -
humus increases acidity of percolating water and accelerates bedrock weathering

Question 4

influences on soil

Answer 4

ultimate driver is plate tectonics
younger soils influenced by the parent rock type
after time, climate is the strongest influence

Question 5

temperate pedalfer types

Answer 5

defined horizon

A pedalfer is the dark, fertile type of soil that will form in a forested region.

Question 6

desert pedocal types

Answer 6

A pedocal is the alkaline type of soil that forms in grassland regions.
drier, temperate areas

Question 7

caliche layer

Answer 7

pedocal is named for the calcite enriched layer that forms. Water begins to move down through the soil layers, but before it gets very far, it begins to evaporate.
Soluble minerals, like calcium carbonate, concentrate in a layer that marks the lowest place that water was able to reach. This layer is called caliche.

Question 8

tropical laterite types

Answer 8

A laterite is the type of thick, nutrient poor soil that forms in the rainforest.
hot, wet, tropical regions, intense chemical weathering strips the soils of their nutrient
practically no humus. All soluble minerals are removed from the soil and all plant nutrients are carried away
All that is left behind are the least soluble materials, like aluminum and iron oxides. These soils are often red in color from the iron oxides.

Question 9

Soil Formation Factors

Answer 9

Thickness varies with -
 latitude 
 topography
 resistance of parent rock
 duration of soil formation

Question 10

Tropical Weathering and Laterite

Answer 10

Hydration, hydrolysis, dissolution and oxidation are maximised under warm wet conditions
mineral ‘leaching’ forms thick layers

Question 11

Laterite

Answer 11

soil

Question 12

saprolite

Answer 12

clay

Question 13

unstable / stable minerals

Answer 13

unstable minerals (eg olivines, feldspars)    stable minerals (eg iron and aluminium oxides, clays)
The end-product (after 10s of 1000s of years) is bauxite or gibbsite

Question 14

Desert Weathering

Answer 14

Thin soils
aridity + lack of vegetation
rare but violent rainstorms remove fine particles

Question 15

Desert Weathering and caliche Concentration of broken bedrock and caliche

Answer 15

product of rare chemical weathering
2 processes and 2 products
1) Evaporation of sporadic near-surface percolating water
subsurface layers
2) Intense evaporation draws up water to the surface
irregular patches

Question 16

Mass Wasting

Answer 16

Mass Movement
Much of the Earth’s surface is unstable - resulting in the downslope movement of blocks, regolith, soil, mud, snow, ice, etc
triggering event unnecessary
slope materials continually weathering and weakening
gravity operates all the time

Question 17

Mass Wasting in rock cycle

Answer 17

Important to the rock cycle
initial step in sediment transport
 significant agent of landscape change
Major transport mechanism -
sooner or later enters river systems  
shallow seas to the deep ocean

Question 18

Slope Stability

Answer 18

Trade-off between - downslope force and resisting force
downslope (weight) –
 rock or regolith
 water
 resisting force -
 	cohesion
 chemical bonds
 electrostatic charges
 surface tension
 friction
gentle and steep slope

Question 19

Slope Stability influences

Answer 19

Angle of repose governed / influenced by
 particle size
 particle shape/surface roughness
the coarser the grain the steeper the slope
 moisture, more moisture the less stable

Question 20

Slope Destablilization

Answer 20

loading by water  (rain)
 grains pushed apart →   disintegration
 lubricates grain contacts/failure surfaces
 removal of vegetation
 slows water drainage
 destabilises soil
 erosion by excessive runoff
steepening the slope by undercutting the foot
initiates rockfall

Question 21

Weak subsurfaces

Answer 21

failure surface
joints parallel to the surface
saturated sand or clay layers
weak sedimentary bedding (shales, evaporites)
metamorphic foliation
prefered orientation in a rock (foliation)
oversteepening and loading play a part

Question 22

creep

Answer 22

creeping down a slope, not really important on large scale
continuous in all terrestrial environments apart from deserts
 expansion and contraction
 	freeze/thaw
 	wet/dry
 grains move -
 perpendicular to slope (expansion)
 	vertical (contraction)
 slope failure is rare

Question 23

slump

Answer 23

initiated by earthquake

Question 24

large mudslides

Answer 24

volcanic ash, rain, carry serious volume, short time on land, long ocean

Question 25

landslides

Answer 25

part of surfaces moved with almost unstppbable power

Question 26

rockfall

Answer 26

tectonically initated

Question 27

Soilfluction

Answer 27

mass movement in tundra
 Defrosted soil layer over permafrost -
 winter freeze/summer thaw
 	downslope creep
 	slope failure is rare

Question 28

Rock Glaciers

Answer 28

high mountains, cold climate
behave like ice glaciers 
 freeze-thaw shattering = copious rock fragments – accumulating faster than ice
 ice builds slowly under fragments
 winter expansion
 summer thaw
 	rocks move downslope
 like stop-motion landslide!

Question 29

Sediment Structure: grain flow

Answer 29

individual grains support each other and keep grain flwoing

occurs in simple dry mass wasting - eg creep, slumping, rockfall

Question 30

Sediment Structure: debris flow

Answer 30

matrix support, little slope, can flow for aaages, rather voluminous ande effective

Question 31

Sediment Structure: liquified flow

Answer 31

due to ascending current, difficult to distinguish
Debris flows and turbidity currents display properties of both dry and fluidised sediment flows
fluidised sediment flow movement occurs on a cushion of air or water – eg avalanche, mudflow

Question 32

Sediment Structure: turbidity flow

Answer 32

urbulent current, extremely strong, house sized floods, proves force of water