erosion methods of sand in the sahel

Question 1

4 types of soil erosion by water

Answer 1

rain splash

sheet wash

rill

gully erosion

Question 2

rainsplash

Answer 2

impact of raindrops on the surface of a soil which is usually the first stage of erosion

the bigger the raindrop, the faster it hits the soil and the bigger the splash causes the soil to be moved further

the removed sediment blocks soil pores resulting in surface crusting and lower infiltration

gravity causes more particles to move downslope rather than upslope.

Question 3

sheet wash

Answer 3

removal of a thin layer of surface of a soil that has already been disturbed by rainsplash

the tiny soil particles which are displaced during rainsplash find their way into soil pore spaces located between soil crumbs and clog them up

the result is the formation of a surface crust (1mm thick), but the rate at which rainwater can now infiltrate the soil is now reduced

it only flows for a few metres before concentrating into rills

usually it results in loss of the finest soil particles (containing nutrients and organic)

Question 4

rill erosion

Answer 4

creation of very small (up to ~30cm) eroded channels across a soil surface

these are the most serious forms of soil erosion by running water

most land surfaces are irregular, with natural depressions, slopes and channels

a sudden burst of rainwater, which is unable to soak into the soil, will flow over the surface, finding its way into natural channels

here it will gather in volume, power and speed as it makes its way down slope, dislodging and moving soil particles down slope as it goes

these can develop into gullies or might be wiped out by the next rainstorm

Question 5

gully erosion

Answer 5

creation of large gullies (metres deep) by large quantities of water flowing over the soil surface

gullies are steep sided water channels which carry water only during rainstorms and, unlike rills, these are usually permanent

water flowing through gullies further erodes the soil by undercutting soil and then slumping

Question 6

3 methods of soil erosion by wind

Answer 6

surface creep:
the slow movement of larger and heavier particles across the surface

saltation:
the bouncing along of lighter particles

suspension:
the lightest particles (dust) blown off ground for up to several hundred kilometres, (can produce dust storms)

Question 7

6 effects of wind erosion of soil

Answer 7

loss of topsoil in one area

deposition of material in another area where it can form topsoil, clog waterways, cause air quality problems…

stunted growth of trees and plants -wind “pruning”

physical damage - especially if carrying sand particles (tall plants may be flattened)

transporting pests

these things lead to a reduction of crop yields and/or quality