1. 10.4 Water’s Effect on Shaping Earth’s Surface
Water is always moving due to the water cycle
Quick changes can happen due to floods, storms or tsunamis
Slower changes occur due to glaciers, run-off and rivers
Water helps in weathering, erosion and deposition
Weathering is the breaking down of rock into smaller pieces
Physical weathering (aka mechanical) - rocks broken down by force, but still remain as the same kind of rocks
Chemical weathering - rocks broken down
by chemicals into different types of matter
Erosion is the movement of pieces of
broken rock to another location
Deposition is the dropping, and
building up, of pieces of rock (eg. river deltas)
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2. Weathering by Water and Ice
Physical weathering
Occurs most quickly where the climate includes high levels of precipitation and large temperature changes (between night and day, and also from season to season)
Ice wedging (aka frost wedging) weathers rocks due to the expansion of water as it freezes
Chemical weathering
Occurs most quickly where climate is warm, there is high levels of rainfall and pollution
Water + oxygen = much chemical weathering, including rusting
aka oxidation
Plants also aid in chemical weathering
Lichens, decomposing plants
See page 389
(c) McGraw Hill Ryerson 2007

3. Weathering by Water and Ice (continued)
Chemical weathering also occurs underground
Water + carbon dioxide = carbonic acid, which dissolves rock
Groundwater becomes acidic, and reacts with calcium carbonate in some rocks to dissolve the rocks
Limestone has high levels of carbonate
Over time, large spaces are created
underground
Sinkholes, caves and karst are
formed this way
See page 390
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4. Erosion by Water and Ice
Moving water breaks down rock into sediment
Sediment can be eroded far away and deposited
V-shaped valleys are carved by flowing water
Rapids create more weathering as water moves faster
Ocean waves continually erode shoreline
Gravity can cause landslides and avalanches
Erosion by ice
Glaciers once covered all of BC (2 km deep, years ago)
leave striations (scratch marks) on rocks
form U-shaped valleys
can move large rocks long distances
See pages
(c) McGraw Hill Ryerson 2007

5. Glacial Effects Arête Cirque Fiord Hanging Valley Horn (or fjord)
Narrow ridge (high ground) between two cirques
Bowl-shaped valley at the head of a glacier
A narrow inlet of ocean between steep cliffs carved by glaciers
U-shaped valley cut off by a bigger valley created by a larger glacier
Pyramid-shaped peak located between three
cirques
See page 394
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(c) McGraw Hill Ryerson 2007

6. Deposition by Water and Ice
After erosion, sediments are eventually deposited
A delta forms where a river empties into a calm basin
Glaciers deposit many different forms of sediment
Erratic
Esker
Moraine
Outwash
Large boulder deposited on the ground by a glacier
Winding ridge of material deposited by a stream running under a glacier
Ridge of rocky material deposited by a glacier, are found at the sides and farthest advance of a glacier.
Material deposited by water from melting glaciers
See page 395
Take the Section 10.4 Quiz
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(c) McGraw Hill Ryerson 2007