Chapter 6 Water

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Chapter 6Water

• Oceans and Freshwater

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Oceans

• 71 of earths surface covered with water
• 97 of the water is in oceans
• In fact there is water around all the land

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• Three major oceans
• Atlantic, Pacific, Indian

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Ocean

• Smaller, bodies of water almost surrounded by
  land are called seas.
• Mediterranean Sea, Black Sea, and Arctic Ocean
  are considered part of the Atlantic Ocean

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Mediterranean Sea
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Oceans

• Pacific is larger than the Atlantic and Indian
  combined
• Atlantic is second largest
• Pacific is deepest ocean
• Indian is second deepest
• Oceans have salt water

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Water Cycle

• The circulation of water from oceans and lakes to
  the air and back.
• Sun heats water
• Water evaporates from ocean
• Leaves dissolved salt behind
• Water vapor is fresh water
• Clouds move the water vapor

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Water Cycle

• Precipitation is falling fresh water
• Rain snow, sleet and hail
• Some water flows back to ocean through rivers and
  streams
• Some seeps into ground to become groundwater

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Ocean Water

• A mixture of water and dissolved gases and solids
• Water is H2O
• 96 of ocean water
• 4 dissolved stuff
• Most elements have been found in ocean water

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Ocean Water

• Sodium chloride most abundant
• Common table salt
• Salinity the number of grams of salt dissolved
  in 1 kilogram of water.
• Units are parts per thousand (ppt)
• If you evaporated 1 kilogram of water with a
  salinity of 35 ppt
• You would have 35 grams of salts

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Ocean Water

• Salinity of ocean water varies from place to
  place
• Between 33 and 37 ppt

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Ocean Water
Sodium chloride 27.2 ppt Magnesium chloride 3.8
ppt Magnesium sulfate 1.7 ppt Calcium sulfate 1.3
ppt Potassium sulfate 0.9 ppt Calcium carbonate
0.1 ppt Magnesium bromide 0.1 ppt
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Sources

• Dissolved materials come from several sources
• Volcanoes add gases, especially chlorine
• Erosion adds dissolved salts
• Rain erodes minerals
• Rivers carry them into ocean
• Source of potassium, sodium and magnesium

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Sources

• Waves dissolve the minerals in the rocks along
  the shore.

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Salinity varies

• It is lower where rivers flow into oceans
• Large rivers like the Mississippi and the Amazon
  have the biggest effect
• Lots of freshwater dilutes the salt water.
• In warm water lots of evaporation makes the water
  have higher salinity
• In polar regions water freezes-
• only fresh water
• leaves the water with higher salinity

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Dissolved Gases

• Most abundant gases are nitrogen, oxygen, and
  carbon dioxide
• Plants use carbon dioxide to make food
• And release oxygen
• Fish breathe the dissolved oxygen
• Varies by depth
• Alot at the surface
• Mixes with the waves
• Sunlight allows plants to exist

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Dissolved Gases

• Varies with temperature of water
• Warm water holds less gases than cold water
• Cold water is more dense- sinks
• In polar region oxygen rich water is carried to
  depths
• Allows fish to live in deep water

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Ocean Temperature

• Sun supplies the heat
• Water temperature is highest at surface
• Waves mixes surface water transfer heat downward
• Region where heat is mixed is called the surface
  zone
• In surface zone temperature is fairly constant
• Surface zone varies in depth

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Ocean Temperature

• Surface zone varies by location
• Caribbean thick
• Off the coast of Maine thin
• Varies with seasons
• Thermocline- region below the surface zone
• Water temperature drops with depth
• Cold deep water doesnt mix with warm surface
  water

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Ocean Temperature

• Deep zone- Extremely cold water from bottom of
  thermocline down
• Three zones vary in thickness
• In Arctic and Antarctic water is so cold there is
  no surface zone

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The Ocean Floor

• Topography- the description of the shape ocean
  floor and its features
• Ocean floor is different from the continents.
• It has higher mountains
• Deeper canyons
• Larger, flatter plains
• Different type of rocks
• More volcanoes

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Continents Edge

• Called the continental margin
• Three parts
• Continental shelf
• Continental slope
• Continental rise

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Continental Shelf

• More like land than ocean floor
• Slopes gently from the shoreline
• Sediments from land are deposited
• Varies in width
• Atlantic 200 km
• Siberia 1200 km

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Continental Shelf

• Many minerals and deposits of gas and oil
• Claimed by countries as part of their boundaries

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Continental Slope

• Floor goes down rapidly- steep slope
• Boundary between continent crust and ocean crust

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Continental Rise

• Slopes more gently
• Made of sediments that come off the shelf
• Turbidity flows carry sediments down.
• Like underwater avalanches of sediment and
  water

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Submarine Canyons

• V shaped valleys cut through shelf and slope
• Caused by turbidity flows
• Bring deep water close to shore
• Monterrey Bay
• Good fishing

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The Ocean Floor
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The Ocean Floor

• Large flat areas are called abyssal plains
• Biggest in Atlantic and Indian oceans
• Because of sediments from large rivers like The
  Mississippi and Amazon and the Ganges and Indus
  Rivers
• Trenches near the edge of continent trap Pacific
  sediments
• Made up of mud silt and clay

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Mountains

• Underwater mountains are called seamounts
• They are volcanoes
• Some rise above to form islands
• Like Hawaiian islands
• Large flat-topped mountains underwater called
  guyots
• Were worn away by waves.
• Then the ocean level rose

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Trenches

• Deep narrow crevices in the ocean floor
• Near the edge of continents
• Deepest is Marianas Trench 11000 m deep

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Midocean Ridge

• Large underwater ocean ranges
• Make one continuous chain around the world
• Formed when molten liquid comes up and forms new
  crust
• Consists of a valley between two parallel
  mountain ranges
• Valley is called a rift valley

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Reefs

• Coral reefs are limestone made by organisms in
  shallow warm water
• Warmer than 18C
• Shallower than 55 m
• Three types of reefs
• Fringing reefs around islands but touching
• Barrier reefs separated from shore by a shallow
  lagoon
• Atoll Reef surrounding a shallow lagoon no island

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Coral Reefs

• Charles Darwin was the first to explain how one
  changed into another.
• Fringing reef forms in shallow water around
  volcanic island
• Water level rises slowly so corals build up, bu
  valocano starts to sink, making a barrier reef
• When volcano is completely gone- atoll

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Ocean Life Zones

• Ocean life affected by
• Amount of sunlight
• Temperature
• Pressure of water
• Three major groups of life
• Plankton- Float near the surface
• Many types of alga
• Source of food for many life forms.

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Ocean Life Zones

• Neckton- ocean life that swims
• Fish , whales , squid, octopus etc.
• Can be predators
• And avoid being prey
• Benthos- live on the ocean floor
• Plants where there is sunlight
• Animals like crab, oyster, star fish

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Ocean Life Zones

• Three major environments
• Intertidal zone- the region below high and low
  tide
• Most challenging for life
• Sometimes underwater
• Sometimes dry land
• Waves breaking on them
• Attach themselves to rocks to avoid being washed
  to sea

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Ocean Life Zones

• Neritic zone- From low tide to the edge of the
  continental shelf.
• About 200 m deep
• Low water pressure, fairly constant temperature
• The most different plants and animals
• Great fishing areas
• Ends when sulight stops penetrating

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Ocean Life Zones

• Two open ocean zones
• Bathyal zone- Begins at continental slope and
  goes down 2000 m
• Little or no sunlight
• Many neckton
• Abyssal zone
• Little food for animals
• Life forms are small and strange looking
• Some produce their own light

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Mapping the Ocean Floor

• The deep ocean is difficult to measure
• High pressure crushes ships
• Earliest method is sounding
• Dropping lines until they hit the bottom
• Inaccurate and slow
• Nets to bring ocean water and life up

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Modern Techniques

• Instruments like underwater cameras
• Underwater robots
• Bathospheres and Bathyscaphs
• Indirect methods like sonar
• Send down sound waves
• They hit bottom and bounce up
• Detect signal
• Use speed of sound to calculate distance

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Freshwater

• Only 3 of all the water
• Of that 85 is ice in glaciers and icecaps
• That water is recycled in the water cycle
• Water evaporates from ocean
• Also evaporates from trees
• And from lakes
• Leaves the salt behind

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Water cycle

• Next water condenses
• Changes back to liquid
• Water must be cooled
• As it rises
• Forms clouds

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Water cycle

• Next there is precipitation
• There are so many water drops it falls out of
  clouds
• Rain snow sleet and hail
• When it hits the ground
• Some evaporates
• Some flows back to ocean
• Some absorbed into ground to become groundwater-
  which flows back to ocean

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Water Cycle
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Frozen Water

• Glaciers form when more snow falls in winter than
  melts in the summer.
• Must be cold
• Over the years snow piles up
• Pressure turns it to ice
• As ice gets thick, it starts to flow
• Glaciers have 2 of the freshwater

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Glaciers

• Those that form in mountains are called valley
  glaciers
• Flow down the valleys
• Rocks in the glacier wear away the valley walls
• Make the valley U-shaped

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Glaciers

• In polar regions ice builds up in thick sheets
• Form continental glaciers
• Cover millions of square kilometers
• Move slowly in all directions
• Found in Greenland and Antarctica
• One time covered much of America
• Icebergs break off glaciers

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Standing water

• Water caught in low places as it runs off
• Ponds and lakes
• Depressions caused by former glaciers are common
  places for lakes
• Or where there are blockages
• Ponds tend to be smaller and shallower than lakes

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Standing water

• Reservoirs are artificial lakes
• Made by damming rivers and streams
• Water backs up
• Used for drinking water, irrigation, recreation,
  and electric power

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Running water

• Precipitation that doesnt soak in flows into
  rivers and streams is called surface runoff
• Some soils soak up more than others
• Have more pore space
• Empty space between particles
• Less runoff
• Plants roots absorb water
• Less runoff

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Running water

• More runoff when there has been recent rains
• Watershed is the land area that drains into a
  river or stream
• Some are huge- like the Mississippi
• Are divided by mountain ranges and ridges

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Watershed
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Groundwater

• Water below the surface
• More fresh water underground than on the surface
• Precipitation move down through spaces between
  the rocks and soil
• Spaces are called pores
• Permeable rock lets water through
• Sandstone- large pores

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Groundwater

• Impermeable rock does not let water through
• Clay small pores
• Water moves downward until it reaches an
  impermeable layer
• Water fills up the permeable layers above
• Where water fills is called the zone of
  saturation
• Where pores are filled mostly with air is called
  the zone of aeration

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Water Table

• Boundary between the zones
• Water table is shallow near the ocean
• In the mountains it can be deep
• Where it rains a lot, it is shallow
• Where it is dry, it is deep
• Shallower in wet season
• Deeper in dry season
• Can be lowered by overuse

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Aquifer

• A layer of underground water flowing horizontally
  through permeable rock
• Trapped above impermeable rock
• Reached by digging wells
• Pollution travels through them easily

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Artesian Well

• If aquifer trapped between two layers of
  impermeable rock,
• Pressure builds up and forms an artesian well
• Water flows out of the ground by itself without
  pumping

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Artesian Well
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Caverns

• Water can slowly dissolve underground rock to
  form open tunnels
• Especially common in limestone
• Acidic water eats through it easily.