Chapter 6 Water Oceans and Freshwater
Oceans 71 % of earths surface covered with water 97 % of the water is in oceans In fact there is water around all the land
Three major oceans Atlantic, Pacific, Indian
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
Mediterranean Sea Black Sea
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
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
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
Ocean Water A mixture of water and dissolved gases and solids Water is H 2 O 96% of ocean water 4% dissolved stuff Most elements have been found in ocean water
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( ppt) If you evaporated 1 kilogram of water with a salinity of 35 ppt You would have 35 grams of salts
Ocean Water Salinity of ocean water varies from place to place Between 33 and 37 ppt
Ocean Water Water, 96.50% Salts, 3.50% 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
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
Sources Waves dissolve the minerals in the rocks along the shore.
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
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
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
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
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 doesn t mix with warm surface water
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
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
Continents Edge Called the continental margin Three parts Continental shelf Continental slope Continental rise
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
Continental Shelf Many minerals and deposits of gas and oil Claimed by countries as part of their boundaries
Continental Slope Floor goes down rapidly- steep slope Boundary between continent crust and ocean crust
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
Submarine Canyons V shaped valleys cut through shelf and slope Caused by turbidity flows Bring deep water close to shore Monterrey Bay Good fishing
The Ocean Floor
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
Mountains Underwater mountains are called seamounts They are volcanoes Some rise above to form islands Like Hawaiian islands Large flat-topped topped mountains underwater called guyots Were worn away by waves. Then the ocean level rose
Trenches Deep narrow crevices in the ocean floor Near the edge of continents Deepest is Marianas Trench 11000 m deep
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
Reefs Coral reefs are limestone made by organisms in shallow warm water Warmer than 18 C 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
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
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.
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
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
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
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
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
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
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
Water cycle Next water condenses Changes back to liquid Water must be cooled As it rises Forms clouds
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
Water Cycle
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
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-shapedU
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
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
Standing water Reservoirs are artificial lakes Made by damming rivers and streams Water backs up Used for drinking water, irrigation, recreation, and electric power
Running water Precipitation that doesn t 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
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
Watershed
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
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
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
Aquifer A layer of underground water flowing horizontally through permeable rock Trapped above impermeable rock Reached by digging wells Pollution travels through them easily
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
Artesian Well
Caverns Water can slowly dissolve underground rock to form open tunnels Especially common in limestone Acidic water eats through it easily.