a note on erosion its causes and controlling measure.

1. Assignment Topic:
Erosion, Causes of erosion and measurement
To control erosion.
Submitted to:
Sir Muhammad Fawad Khan
Submitted by:
Samiullah/ Adeel Azam
Roll no:
5208/
Semester:
4th
Section:
A/B
Department:
Geology
UNIVERSITY OF HARIPUR

2. EROSION
Introduction:
Erosion is a natural process Which is usually made by rock and soil Being loosened from earth`s
surface at one location and moved to another. Erosion changes the landscapes by wearing down
mountains, filling in valleys and making rivers appear and disappear. But erosion can be speeded
up by human activities as farming and mining. Erosion begins with a process called weathering.
In this process, environmental factors break rock and soil into smaller pieces and loosen them
from earth surfaces. One of the most powerful causes of erosion is water. Tectonic movement
can also contribute to erosion, as can the wind. Wind transports materials from one place to
another, and in extremely windy locations it can contribute a powerful scouring force to the
process of erosion. Materials also naturally tend to slide down a slope, in a process called mass
wasting. Humans can also bring about erosion, usually through poor land management,
overgrazing the word erosion comes from the Latin word "erosionem" which means “a gnawing
away”
DEFINATION
The process of eroding or being eroded by wind, water, or other natural agents.
SOIL EROSION
When a raindrop hits soil that is not protected by a cover of vegetation and
where there are no roots to bind the soil, it has the impact of a bullet.
Soils particles are loosened washed down the slope of the land and
either end up in the valley or are washed away out to sea by streams and
rivers.
CAUSES OF EROSION
There are many different forces in nature that cause erosion. Depending on the type of force,
erosion can happen quickly or take thousands of years. The three main forces that cause erosion
are water, wind, and ice
1. Stream erosion
A stream usually erodes rocks and sediments over which it flows. Streams are one of the most
effective sculptors of the land. The particles of rocks and sediments that a stream picks up are
carried along to be deposited further downward. Streams deposits rocks and sediments in three
ways
I. Hydraulic Action
II. Solution
III. Abrasion

3. I. Hydraulic action
Hydraulic action refers to the ability of flowing water to pick up and move rock and
sediments. Therefore of running water swirling made crake in the rock and break and loosed
the sediment which then carried by stream. Hydraulic action can also erode loose material
from stream bank on the outside of the curve.
II. Solution
Although ordinarily slow, can be effective process of weathering and erosion. A stream
flowing over limestone gradually dissolves the rock deepening the stream channel. A stream
flowing over other sedimentary rocks such as sandstone can dissolve calcite cement. Loosing
grains that can then be picked up by hydraulic action.
III. Abrasion
The erosive processthatismostlyeffective onarocky streambed.The grindingawayof the stream
channel bythe fractionand impactof the sedimentload.Sandandgravel tumblingalongnearthe
bottomof a streamwearaway fromthe stream.The abrasionof sedimentsonthe streamis
generallymuchmore effectiveinwearingawaythe rockthanhydraulicactionalone.
These loose sediments are then transported by water and then deposited on another place form
valleys mountains etc
 Rainfall: Rainfall can cause erosion both when the rain hits the surface of the Earth, called
splash erosion, and when raindrops accumulate and flow like small streams.
2. Glacial erosion

4. The rocks at the base and sides of a glacier may have been fractured by tectonic forces and may
be loosened by weathering processes, such as frost wedging or pressure release fracturing. The
moving ice then dislodges the loosened rock in a process called plucking. Ice is viscous enough
to pick up and carry particles of all sizes. Thus glaciers erode and transport huge quantities of
rocks and sediments. Ice itself is not abrasive to bed rock because it is too much soft. However,
rocks embedded in the ice scrape across bedrock like a sheet of rough sandpaper. This process
cut deep, parallel grooves and scratches in bed rock called glacial striations. When glaciers
melts and striated bedrock is exposed, the markings show the direction of ice movement. These
are used to map the flow directions of the glaciers.
3. Wind erosion
Erosion by wind is a complex process that involves sorting, transport, abrasion and deposition of
sediments. Turbulent winds above a threshold velocity (13 miles per hour at one foot above the
ground) blowing over erodible soil can cause erosion. Wind transport soil particle in three ways.
Saltation. Individual particles are lifted off the soil surface by wind; then they return and
dislodge other particles. 50 percent to 80 percent of total transport is by saltation.
Suspension. Dislodges particles, small enough to remain airborne for an extended period of
time, are as visible as dust but generally make up less than 20 percent of the total soil
transported.
Creep. Sand sized particles are set in motion by saltation. These sand sized particles creep
slowly along the surface. Up to 25 percent of the total transport may be from creep.

5. EROSION CAUSED BY HUMAN
1) Deforestation: deforestation is burning or cutting of forest. Removal of the vegetation
covering the ground causes the soil, which is unprotected against wind and water, to erode.
2) Watering: Watering gardens and lawns also causes erosion. When using a garden hose or an
irrigation system, the water hits the ground with enough force to cause the soil to erode.
3) Agriculture: Agriculture is the main way humans cause soil erosion. When vegetation is
planted in the ground, the topsoil is shifted, which causes erosion. The loose topsoil is then
carried by wind and water which is then deposited in other place.
MEASUREMENT TO CONTROL EROSION
1. Mulching: mulching is the covering of the soil with crop residues such as straw, maize,
stalks etc. these cover protects the soil from the rain drop impact and reduces the velocity of
runoff and wind.
2. Multiple cropping: the aim of multiple cropping is to increase the production from the land
whilst providing protection of the soil against erosion. It includes:
1. Rotation: growing different crops consequently in rotation reduces erosion as high rate
of soil loss under row crop is counteracted by low rates under other crops.
2. Strip cropping: row crops and protection effective crops (legumes and grasses) are
grown in alternate strips aligned on the contour or perpendicular to the wind.
3. Agro forestry: Trees can be incorporated within a farming system by planting them on
terraces, contour bounds and as ornamental around the homestead. This reduces soil erosion and
provides additional needs to the farmers

6. Fig: Agro foresting
4. Reforestation: vegetations play the major role in erosion control on gullies areas and
landslides
5. Continued covering: - Once the land is naked there is high possibility of soil erosion. Hence
the land should be kept covered all round the year.
6. Inter cropping: - In this method, the spaces among the tree species are covered with
agriculture crops, which help in soil and water conservation.
7. Mixed cropping: - In this system two or more than two crops are raised in the same land and
in the same time. The benefit is that due to different kind of roots, soil is protected more
perfectly.
8. Terracing: - In hilly areas, the farming should be done only when the land is terraced
properly because without terracing the run-off is increased and soil is easily eroded.
Fig: Terrace
9. Barriers: Unsheltered distance across a field is reduced by installing vegetative barriers at
right angles to the prevailing erosive winds. These barriers reduce the soil transported by:
Providing a stable barrier to stop saltation of soil particles,
Trapping soil particles creeping along the ground, and

7. Reducing wind speeds below the threshold velocity along the ground for a distance of ten times
(10x) the barrier height. This horizontal distance is sheltered from the wind, reducing the
distance in a field where wind exceeds the threshold velocity
10. Ridges; Ridging the soil surface can also be an effective practice. Ridges absorb and deflect
wind energy and trap moving soil particles. Ridges with an ideal height to spacing ratio of 1:4
are most effective when constructed at right angles to the prevailing erosive wind. Ridges 4
inches high spaced 16 inches apart will provide optimum protection if oriented correctly.
Fig: Ridges in field
REFRENCES
1: Physical Geology by Diane Carlson (author), Charles (Carlos) C Plummer, Lisa
Hamersley (author)
Chapter 16: Stream and floods 384, Chapter 18: Desert and wind action 446
Chapter 19: Glaciers and Glaciations 468
2: Principle of Agronomy by S.R. REDDY
Chapter 4: SOIL AND WATER CONVERSATION
3: How Do Humans Cause Erosion?
By Calia Roberts, eHow
4: Earth Sciences by Edward J.Tarbuck and Frederick K. Lutgens
Chapter 6 Glaciers, Desert and wind Page 157