9. Erosion by Water
Moving water is the major
agent of erosion. Rain carries
away bits of soil and slowly
washes away rock fragments.
10. • Four primary types of erosion that occur as a
direct result of rainfall:
1. Splash erosion - the impact of a falling
raindrop creates a small crater in the soil,
ejecting soil particles.
2. Sheet erosion - the transport of loosened soil
particles by overland flow.
11. 3. Rill erosion - refers to the development of
small, ephemeral concentrated flow paths
which function as both sediment source
and sediment delivery systems for erosion on
hillslopes.
4. Gully erosion - occurs when runoff water
accumulates and rapidly flows in narrow
channels during or immediately after heavy
rains or melting snow, removing soil to a
considerable depth.
15. A spoil tip covered in rills and gullies in Rummu, Estonia
16.
17. Erosion by Water
Rushing streams and rivers
wear away their banks,
larger
creating larger and
valleys.
18. Streams erode their banks in three different
ways:
1) the hydraulic action of the water itself
moves the sediments,
2) water acts to corrode sediments by
removing ions and dissolving them, and
3) particles in the water strike bedrock and
erode it.
19. The water of streams can erode in three
different places:
1) lateral erosion erodes the sediment
on the sides of the stream channel,
2) down cutting erodes the stream bed
deeper, and
3) headward erosion erodes the channel
upslope.
20.
21.
22.
23.
24. Erosion by water changes the shape of
coastlines. Waves constantly crash
against shores. They pound rocks into
pebbles and reduce pebbles to sand.
Water sometimes takes sand away from
beaches. This moves the coastline farther
inland.
Erosion by Water
25. Waves in oceans and other large
bodies of water produce coastal erosion.
The power of oceanic waves is awesome,
large storm waves can produce 2000
pounds of pressure per square foot. The
pure energy of waves along with the
chemical content of the water is what
erodes the rock of the coastline.
Erosion by Water
26.
27. The battering of ocean waves also
erodes seaside cliffs. It sometimes bores
holes that form caves. When water breaks
through the back of the cave, it creates an
arch. The continual pounding of the waves
can cause the top of the arch to fall,
leaving nothing but rock columns. These
are called sea stacks. All of these features
make rocky beaches beautiful, but also
dangerous.
60. Erosion by wind is known as Aeolian
erosion and occurs almost always in
deserts. Aeolian erosion of sand in the
desert is partially responsible for the
formation of sand dunes. The power of
the wind erodes rock and sand.
Erosion by Wind
61.
62.
63.
64.
65.
66. In dry areas, windblown sand blasts
against rock with tremendous force, slowly
wearing away the soft rock. It also polishes
until
rocks and cliffs
Wind is responsible
they are smooth.
of the dramatic
arches.
Erosion by Wind
80. The erosive power of moving ice is
actually a bit greater than the power of
water but since water is much more
common, it is responsible for a greater
amount of erosion on the earth's surface.
Erosion by Ice
81. Glaciers erode predominantly by three
different processes:
• Abrasion/Scouring
• Plucking
• Ice Thrusting
Erosion by Ice
82. The rocks carried by a glacier rub against
the ground below, eroding both the ground
and the rocks. Glaciers grind up rocks and
scrape away the soil. Moving glaciers gouge
out basins and form steep-sided mountain
valleys. Eroded sediment is often visible on
and around glaciers. This material is called
moraine.
Erosion by Ice
91. Mass movement is the downward and
outward movement of rock and sediments on
a sloped surface, mainly due to the force
of gravity. Mass movement is an important
part of the erosional process, and is often the
first stage in the breakdown and transport of
weathered materials in mountainous areas.
Gravitational Erosion
92. Wadi in Makhtesh Ramon, Israel, showing gravity collapse erosion on its banks.
93. Exfoliation
• a type of erosion
that occurs when a
rock
heated
is rapidly
up by the
sun. This results in
the expansion of
the rock.
94. Lightning
When water in cracked rock is rapidly heated
by a lightning strike, the resulting steam
explosion can erode rock and shift boulders. It
may be a significant factor in erosion of tropical
and subtropical mountains that have never
been glaciated. Evidence of lightning strikes
include craters, partially melted rock and
erratic magnetic fields.
95. Factors affecting erosion rates
• Precipitation and
wind speed
• Soil structure and
composition
• Vegetative cover
• Topography
Human activities
• Agricultural
practices
• Deforestation
• Roads and
urbanization
• Climate change
99. Prevention and Remediation
The most effective known method for
erosion prevention is to increase vegetative
cover on the land, which helps prevent both
wind and water erosion.
Terracing is an extremely effective means
of erosion control, which has been practiced for
thousands of years by people all over the
world.
100.
101.
102. Prevention and Remediation
Windbreaks (also called shelterbelts)
are rows of trees and shrubs that are
planted along the edges of agricultural
fields, to shield the fields against winds.
