Transcript Ch.10 Water Review

10.1 Distribution of Water
• Water exists everywhere on Earth, and covers 70% of
its surface. 97% of this water is found in the oceans.
 Another 2% is ice and snow, leaving only 1% as fresh water
found in the ground, rivers, lakes and streams.
 Finding fresh water to drink is a challenge in many places, as
most fresh water is under the ground.
See page 362
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The Water Cycle
• Earth is the only planet with water in all 3 states
• Water is continually cycling through the water cycle
Solid  Liquid = Melting
Liquid  Gas = Evaporation
Gas  Liquid = Condensation
Liquid  Solid = Solidify/Freeze
Solid  Gas = Sublimation
Gas  Solid = Deposition
• Heat energy from the Sun causes these changes to
drive the water cycle.
See page 364
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The Water Cycle (continued)
• The water cycle occurs everywhere, not just oceans
 Water evaporates when it is warmed, and then condenses in
the atmosphere as clouds
when it cools and falls as
precipitation. The water
then runs-off back to
storage basins, or soaks
into the ground.
 A hydrologist is a scientist who studies water systems
 An oceanographer studies oceans specifically
See pages 404 - 405
Take the Section 10.1 Quiz
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10.2 How Ocean Water Differs
from Fresh Water
• Ocean water’s salinity = 200X greater than fresh water
 Average salinity of oceans is 35 parts per thousand
 Oceans at equator (evaporation) and poles (ice) have the
highest salinity (removing water increases salinity)
 Ocean locations near rivers have low salinity, due to addition
of fresh water
See page 368 - 370
from the World Ocean Atlas 2001
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Composition of Salt Water
• Salt water is composed of minerals dissolved during
run-offs occurring over millions of years
 Volcanic eruptions also release minerals from inside Earth
 Sodium ions (Na+) and
chloride ions (Cl-) are most
common solids in ocean water
 Na+ ions and Cl- ions > 75% of
all solids in ocean water
 Mixed and joined in the ocean,
NaCl is chemical name for salt
See page 370
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Density of Salt Water
Mass (kg)
• Density of ocean water (kg / m ) =
Volume (m3 )
3
 Density = how tightly packed the molecules are in an object
 Less dense always floats on more dense
 Eg. warm air rises above cool air, and oil floats on water
 We float better in salt water than
fresh water
• Salt water has slightly different
properties than fresh water
 Salt water freezes at –1.9 ºC
Take the Section 10.2 Quiz
See page 371
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10.3 Sources of Fresh Water
• Precipitation becomes run-off as gravity pulls water
down into the groundwater, a lake or an ocean basin.
• Run-off increases if:
 precipitation falls on rock, as soils allow water to soak in
 heavy rainfall saturates the ground so water can’t soak in
 long periods of rainfall saturate the ground so
water can’t soak in
 water can flow quickly down a steep slope, not
having time to soak in
 there is no vegetation, as plants help to absorb
water and hold soil with their root systems
See page 376 - 377
 there is human development and no soils
• Human development often alters run-off
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Drainage Basins
• Drainage basins are large areas where surface water
all moves towards one main river
 Run-off flows into streams and
smaller rivers, which are
tributaries of large rivers,
forming a branching system
 Large rivers are separated by very
high ground called divides
 The Rocky Mountains form the
Continental Divide, which divides
BC and Alberta
See page 379
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Ground Water
• Ground water is water that soaks into the ground
 Rock/ground with good porosity allows more water to enter
 More pores (spaces in the rock/soil), the better the porosity
 An aquifer is a layer of porous rock that allows ground water
to flow, almost like a river below the surface.
• Humans get fresh water from
 Reservoirs, natural or man-made
 Wells, drilled into aquifers down
to the water table, which is the
top level of the zone of saturation.
 The water table is very deep in
deserts, but near the surface in swamps
 The water table rises during wet seasons
See page 380
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Glaciers
• Almost 66% of all fresh water on Earth is in glaciers
 Glaciers form from layers of snow falling over many years
 Glaciers melt slowly under their own weight, and slowly flow
downhill
 Glaciers cover about 10% of the Earth’s surface
 Alpine glaciers (aka valley) found in mountains
 Continental glaciers (aka ice sheets) cover huge areas of
land.
 Eg. Greenland and Antarctia
 Glaciers flow until they
 reach an ocean, where crevasses open and icebergs fall off
 reach an area where warm temps allow as much melting as
See page 381
re-freezing, or recede ifTake
they
faster
themelt
Section
10.3 Quiz
(c) McGraw Hill Ryerson 2007
than they can freeze
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
See page 386 - 388
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
• 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
See page 389
 Lichens, decomposing plants
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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
QuickTime™ and a
TIFF (Uncompressed) decompressor
 Sinkholes, caves and karst are
are needed to see this picture.
formed this way
See page 390
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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
• 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
See pages 392 - 393
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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