Weathering

Question 1

What does the Peltier diagram illustrate?

Answer 1

The Peltier diagram illustrates the relationship between temperature and rainfall, and the different weathering types.

Question 2

Explain how the climate affects weathering?

Answer 2

-TEMPERATURE and PRECIPITATION play an important role in weathering.

-Some climates accelerate certain types of weathering, and other make weathering impossible to occur.

-For example, in ALPINE CLIMATES where temperatures fluctuate more rapidly than in polar environments, so freeze-thaw weathering is more severe. Also, salt crystal growth favours DRY CLIMATES, allowing the water to evaporate and leave salt crystals.

Question 3

Explain how rocks type and structure affects weathering?

Answer 3

-The TYPE and STRUCTURE of rock dictates the rate at which weathering will occur, and also what type of weathering. Some rock (e.g. water soluble rocks such as limestone) are more vulnerable to chemical erosion, and therefore will be weather at a faster rate.

-Permeable rocks types (e.g. Sandstone and chalk) have PORES that can leave it vulnerable to many types of weathering (e.g. freeze-thaw weathering).

-Impermeable rocks (e.g. slate and marble) may have lower rates of weathering because more energy is required to break down the rock.

Question 4

Explain how vegetation affects the rate of weathering?

Answer 4

The TYPE and AMOUNT of vegetation affects weathering in multiple ways. For example, ROOT-ACTION weathering will be at a much higher rate in areas with high vegetation, especially large vegetation such as trees (which have roots capable breaking apart even hard rock). Root action is very prevalent in the rainforests (e.g. The Amazon Rainforest) due to an ABUNDANCE OF VEGETATION.

Question 5

Explain how relief affects the rate of weathering.

Answer 5

Relief affects the RATE and TYPE of weathering that occurs. Area of more GENTLE relief are likely to be subjected to STANDING WATER and water that INFILTRATES into the ground. In contrast, in areas of STEEP RELIEF it is more common for precipitation to fall as OVERLAND FLOW. This means that the multiple types of weathering caused by precipitation may be at a lower prevalence.

Question 6

Heaves are the…

Answer 6

slowest and most prevalent form of mass movement

Question 7

How do heaves form on cohesive materials?

Answer 7

On slopes made of cohesive materials, gravity causes the soil to ripple, creating steps called terracettes.

Question 8

Where do frost heaves occur and how do they form?

Answer 8

Frost heaves occurs in colder regions, where water in the soil freezes, and heaves rocks and soil particles upwards. The particles then fall downwards under the influence of gravity. When this occurs on a slope, it can create lines of stones, called stone stripes.

Question 9

On what type of slopes do flows occur and what are slopes flows faster than?

Answer 9

Flows occur on slopes made from cohesive materials (e.g. Slits and Clays)

Flows are faster than heaves, but not as fast as slides and falls.

Question 10

What are flows controlled by and when do mudflows occur?

Answer 10

Flows are controlled by moisture within the slope. When soil becomes saturated, the cohesive bonds within the soil break, causing soil to move downhill like a viscous liquid.

Mudflows often occur under heavy rainfall conditions, especially rainfall that falls within short periods of time (leading to less infiltration and percolation into groundwater stores).

Question 11

On what type of slopes do falls occur and how fast to rock falls occur?

Answer 11

Falls occur on slopes made from rocks.

Rock falls happen very suddenly, and the effects are usually dramatic due to strong internal strength of rocks, the slopes can be very steep.

Question 12

How can be rock falls be triggered?

Answer 12

Rock falls are triggered in many ways. However, rock falls are not as dependent on rainfall unlike flows, as the internal strength of rocks is affected by the presence of water, to the extent of silts and clays. Rock falls can be triggered by freeze-thaw processes, seismic waves, or gravitational stress.

Question 13

What are rockslides and where do they occur?

Answer 13

Rockslides are a type of landslide that occur on slopes made from rocks. Rockslides occur along faults in the rock. They have a fast movement.

Question 14

How do rockslides/landslides occur? Also, describe the movement of a rockslides.

Answer 14

Similarly to rock falls, landslides can be triggered by SEISMIC WAVES or GRAVITATIONAL STRESS. Rockslides have a fast movement and a large scale, causing a great deal of material to be moved in a short space of time.

Question 15

What is slope instability caused by?

Answer 15

Slope instability is generally cause by either: an increase in external stress on the internal strength of a slope.

Question 16

How can mining cause mass movement?

Answer 16

Mass movement as a result of mining and quarrying is FREQUENT. Mining and quarrying REMOVES SUPPORT from the slope, be that UNDERLYING SUPPORT or LATERAL SUPPORT. This therefore cause instability within the slope, often leading to landslides, mudslides, rockfalls, or rockslides.

Question 17

How can tourism cause mass movement?

Answer 17

Tourism is prevalent in hillslope areas, especially alpine slopes where skiing is common. Tourism creates stress on hillslopes in multitude of ways. For example, Erosion of the slope is dramatically increased due to trampling of vegetation, skis, heavy machinery, walking etc. which damages and compacts the soil. Thus, there is an increased external stress on the slope.

Question 18

How can deforestation cause mass movement?

Answer 18

Deforestation can cause major slope instability of not properly managed. Deforestation decreases the interception of precipitation, causing more water to flow over the hillslope an infiltrate into it. Less water is also being taken up by tree roots, increasing the SATURATION of the soil further. This can cause erosion as well as triggering mass movement, mass movement.

The shear strength of the slope of slopes are enhanced by roots of trees. So, deforestation reduced the internal strength of slopes.

Question 19

How can afforestation increase the stability of slopes?

Answer 19

Roots from trees increase the internal strength of the soil, meaning the slope can take more sheer stress before it fails.

More trees reduce the saturation of the soil, both from intercepting precipitation and taking up water from roots. Not only does this reduce the risk of mass movement triggered by high soil saturation levels (like mudslides), but it also decreases erosion caused by water which also compromises the internal strength of the slope.

Question 20

How can rock bolting increase slope stability?

Answer 20

Rock bolting is where bolts are drilled into rock slopes in a specific pattern, which transfers the load from the weaker exterior to the stronger interior of the slope. This reduces the risk of rockfalls and rockslides. Rock bolting works to ‘knit’ the slope together to increase its internal strength.

Question 21

How does grading increase slope stability?

Answer 21

Grading is the process of RESHAPING the surface of a slope to SPECIFIED SLOPE. This is done using heavy machinery, such as excavators and graders. The purpose of grading is to provide a more uniform topography (e.g. for controlling surface run off or minimising erosion). Grading can work to reinforce the slope so that the mass movement processes are less likely to occur.

Question 22

Slope failure is caused by…

Answer 22

An increase in shear stress and a decrease in shear strength.