Weathering + Mass Wasting

Question 1

Denudation

Answer 1

removal, wearing away, disintegration of rock material

Question 2

3 types of denudation in order

Answer 2

1) weathering = breaking down of rock into smaller pieces by atmosphere
2) mass wasting = short distance VERTICAL movement of broken rock material
3) erosion = (horizontal) removal, transportation, deposition of rock material over wider areas

Question 3

What are rock openings

Answer 3

1) Microscopic openings
2) joints
3) faults
4) lava vesicles
5) solution cavities

Question 4

Microscopic openings

Answer 4

1) consist of spaces between crystals of igneous or metamorphic rocks

Question 5

Joints

Answer 5

VERTICAL Cracks that develop as a result of stress BUT rocks do not show noticeable displacement along breaks
most important of all rock openings in facilitating weathering

Question 6

Bedding Plane

Answer 6

horizontal crack (similar to joint BUT not vertical)

Question 7

Faults

Answer 7

Breaks in bedrock caused by forced displacement of rock structure

Question 8

Lava vesciles

Answer 8

holes of various sizes that develop in cooling lava when gases aren’t able to escape

Question 9

solution cavities

Answer 9

holes formed in carbonate rocks (limestone) by soluble minerals dissolving + being carried away

Question 10

Joints vs faults

Answer 10

Joints = no displacement
Faults = displacement

Question 11

Types of weathering agents

Answer 11

1) mechanical
2) chemical
3) biological

Question 12

Mechanical Weathering

Answer 12

1) Physical disintegration of rock without changing composition
(grinding)
2) occurs at surface 3) Examples:
- frost wedging (cold places) or salt wedging (hot places w. capillary reaction)
- temp changes (think wildfires) cause rocks to expand + weaken –> mini fractures form
- exfoliation = curved layers peel off bedrock, creating shapes like Halfdome (need bedrock)
- biotic processes = plant roots can spread rocks apart

Question 13

Chemical Weathering

Answer 13

1) decomposition of rock by chemical alteration of minerals
2) requires moisture + surface area –> finely grained materials decompose more rapidly

Question 14

Examples of chemical weathering

Answer 14

1) oxidation = when oxygen (in water) comes into contact with rock –> produces iron oxide
2) Hydration = water added to compound + becomes part of it –> forms hydrates (increases volume, contribute to disintegration)
3) hydrolysis = water added to compound + breaks it up i.e. silicate materials
4) carbonation = carbon dioxide dissolved in water, producing carbonic acid –> reacts with carbonate rocks to produce calcium bicarb –> forms stalagmites/tites
5) spheroidal weathering = thin rock layers peel off boulders, rounding it. outcome of hydration

Question 15

Biological Weathering

Answer 15

1) weathering that involves living organisms
2) examples = plant roots into cracks + crevices
3) lichen remove minerals from rock + alternate btwn wet/dry, weakening rock –> leading to weathering
4) burrowing by animals

Question 16

Weathering in diff climates

Answer 16

1) High temps + abundant precipitation = lead to more weathering
2) moisture more important than temp
3) desert regions = more mechanical than chem. weathering bc lack of water
$4) shallow weathering in tundra/desert + deep weathering in trop. rainforest

Question 17

What factors influence mass wasting

Answer 17

1) angle of repose
2) water
3) clay
4) permafrost

Question 18

Mass wasting factor = angle of repose

Answer 18

1) angle of repose = steepest angle where rocks/soil don’t slide off
2) balance between gravity + cohesion of rock to surface

Question 19

Mass wasting factor = water

Answer 19

1) addition of water = lubricating medium + diminishes friction btwn particles
2) reduces angle of repose

Question 20

Mass wasting factor = clay

Answer 20

1) clay becomes very slippery when absorbs water
2) quick clays = change from solid mass to near liquid very quickly

Question 21

Mass wasting factor = permafrost

Answer 21

contributes to mass wasting in subarctic regions + high latitudes

Question 22

Types of mass wasting

Answer 22

1) fall
2) slide
3) flow
4) creep

Question 23

Mass wasting = fall

Answer 23

1) falling of rock downslope
2) Rock that falls called talus
3) dry + fast

Question 24

Slide

Answer 24

1) abrupt + rapid
2) top of hill has a deep scar –> exposed bedrock + debris
3) more moist than fall –> if extremely moist it’s mudflow

Question 25

Flow

Answer 25

1) becomes unstable because absorption of water + moves downhill 2) can vary in speed, depending on friction 3) gravity is impelling force + water is catalyst 4) Earthflow = portion of water-saturated slope moves downhill 5) mudflow = rapid movement of wet material through canyon/valley + deposited in fan-shape

Question 26

Creep

Answer 26

1) slowest + dry 2) very gradual downhill movement of regolith that hard to notice 3) occurs mostly on steep lightly vegetated slope 4) caused by freeze/thaw cycles --> freezes moved upward bc of increasing vol of ice BUT when it thaws particle settles slightly downslope

Question 27

Solifluction

Answer 27

1) Special form of creep 2) restricted to high latitude + high elevation tundra 3) thaws BUT water not able to penetrate permafrost, so active layer (Above frost) becomes oversaturated + moves downhill

Question 28

Differential weathering

Answer 28

1) All rock does not weather at same rate or to same extent 2) some rocks easily weathered --> weak 3) other rocks --> stronger + more resistant to weathering

Question 29

What are agents of erosion

Answer 29

1) wind 2) water (biggest factor) 3) ice

Question 30

A Climate weathering type

Answer 30

1) Chemical - hot + lots of water draining through --> lots of oxygen WHICH is why there is lots of oxidation --> laterization = red soil (bc of iron) 2) No mechanical = too hot for frost wedging + not enough bedrock for exfoliation

Question 31

E Climate weathering type

Answer 31

1) No chemical = standing water --> soil is saturated + no oxygen --> no chemical reactions 2) mechanical = frost wedging + temperature fluctuations

Question 32

B, C, D Climate weathering type

Answer 32

1) BOTH MECHANICAL + CHEMICAL *B climates = mainly mechanical since not enuf water for chemical weathering*

Question 33

Describe how mass wasting varies by moisture + speed

Answer 33

1) As you add moisture: rockfall --> landslide --> mudslide 2) Speed: Solifluction (slowest) --> earthflow --> mudflow 3) Slowest + driest = creep (poles tilting bc ground moves v slowly) **FLOWS NEED WATER**