Transcript WATER`S EFFECT ON SHAPING EARTH`S SURFACE

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
See page 386 - 388
(c) McGraw Hill Ryerson 2007
Water’s Effect on Shaping Earth’s
Surface
• 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)
(c) McGraw Hill Ryerson 2007
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
See page 389
(c) McGraw Hill Ryerson 2007
Weathering by Water and Ice
• 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
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Weathering by Water and Ice
• 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
QuickTime™ and a
TIFF (Uncompressed) decompressor
 Sinkholes, caves and karst are
are needed to see this picture.
formed this way
See page 390
(c) McGraw Hill Ryerson 2007
Erosion by Water and Ice
• Erosion by water
 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
See pages 392 - 393
(c) McGraw Hill Ryerson 2007
Erosion by Water and Ice
• Erosion by ice
 Glaciers once covered all of BC (2 km deep, 10 000 years ago)
 leave striations (scratch marks) on rocks
 form U-shaped valleys
 can move large rocks long distances
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Glacial Effects
Arête
Narrow ridge
(high ground)
between two
cirques
Cirque
Bowl-shaped
valley at the
head of a glacier
(or fjord)
Hanging
Valley
Horn
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
Fiord
See page 394
Images from http://pubs.usgs.gov/of/2004/1216/a/a.html
(c) McGraw Hill Ryerson 2007
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
Images from http://pubs.usgs.gov/of/2004/1216/a/a.html
(c) McGraw Hill Ryerson 2007