Erosion
Science 8
1. Give a 3 point definition for the words erosion and sediment.
erosion
Rocks and soil are worn
away by water or wind
Riverbanks get washed
away during floods.
Freeze-thaw cracks break
up large rocks.
Wind blows soil.
Wind blows sand particles
that erode rock.
“Slipping away”
“weathering”
sediment
Sediment is rock or soil
carried in water or
deposited somewhere by
water.
2.
Sediment in rivers makes
them look cloudy or
muddy.
“layers”
“rock particles”
“deposits”
Sediment is also layers of
material deposited by
water.
What are two problems caused by sediment in water?
Water plants get less light and some fish don’t get enough oxygen
3.
What prevents soil erosion in natural environments?
Plant and their roots.
4. Describe two ways that vegetation reduces soil erosion.
Plant roots hold the soil in place and plants protect the soil from rain
(splashing).
5.
a) What type of erosion control is shown in this
diagram?
Contour ploughing
b) Why does this method of farming lead to less
soil erosion?
The sediment only travels a short
distance before the water sinks in.
c) Why do you think hedges (bushes) are
planted at the top and bottom of the field?
http://tilz.tearfund.org/Publications/Footsteps+1120/Footsteps+15/How+soil+erosion+happens.htm
The roots of the plants hold the soil in place.
6. a) In the diagram below, use an arrow to label the area where erosion would
probably occur and explain why.
b) Label the area where deposition occurs and explain why.
c)Circle the area that is the estuary.
Erosion
happens in the
mountains
where the
river runs
fastest (steep
slopes)
Deposition
happens near
the delta
(flatter and
the river is
slower).
ESTUARY
7. What is dredging and why is it done?
It means digging up the bottom of a river so ships can pass
through safely
8. a) What are levees?
Levees are long walls of earth built along riverbanks (prevent floods)
b) What problem could be caused by levees?
If it breaks, you get a sudden flood of very fast moving water (faster
water does MORE damage)
9. In the picture below, a boulder is shown that has begun to erode through freeze –
thaw cycles. Where do people often have problems with freeze-thaw damage?
Anything that we build (roads,
bridges, sidewalks, walls) and in
pipes that carry water.
http://www.mostreamteam.org/activity_guide/flood_plains/floodPlains_functions.htm