Earths Oceans

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The Worlds Oceans

• 71 of the Earths surface is covered by ocean
  water.
• The oceans contain 97 of the earths water.
• All the oceans and seas are actually one
  continuous body of water.

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Oceans

• The oceans are the Atlantic, Pacific, Indian.
  Arctic and Southern.
• The Pacific Ocean is the largest ocean.
• The area and volume of the Pacific Ocean are
  greater than the Atlantic and Indian combined.

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Seas

• A sea is a part of an ocean that is nearly
  surrounded by water.
• The Mediterranean, Arctic and Black Sea are
  really part of the Atlantic Ocean.

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Water Cycle

• The suns rays heat the surface of the ocean.
• The heat causes the water to evaporate.
• The evaporating water (clean, fresh water) enters
  the atmosphere as water vapor.
• The salt remains behind.

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Water Cycle

• Winds carry water vapor over land.
• Some of the water vapor condenses to form clouds.
• The water in the clouds falls as precipitation.

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Water Cycle

• Some of this water runs into rivers and streams
  which flow back into the oceans.
• Some of the water seeps into the soil and rocks
  become part of the groundwater.

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Properties of Ocean Water

• Ocean water is a mixture of gases and solids
  dissolved in pure water.
• Oceanographers believe oceans contain all the
  natural elements on Earth.
• 85 of 90 have been found in the ocean.

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Major Elements in the Ocean

• Ocean water is 96 pure water.
• Chlorine (1.9) and sodium (1.1) make up the next
  largest concentration of elements.
• Sodium chloride is table salt.

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Salinity

• Salinity describes the amount of dissolved water
  in the ocean.
• Salinity is expressed in parts per thousand.
• The salinity level of the ocean is expressed in
  parts per thousand.
• The average salinity of ocean is 35 parts per
  thousand.

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Sources of Salt in the Ocean

• When volcanoes erupt, rock materials and gases,
  such as chlorine, spew forth.
• As rivers, streams and glaciers move over rock
  and soil, they dissolve salts, such as magnesium,
  sodium and potassium, in them.
• As waves pound the shoreline, they dissolve salts
  from the rocks.

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Salinity Levels

• The salinity is lower in areas where freshwater
  rivers run into the ocean. Salinity levels are
  also affected by animals such as clams and
  oysters that use calcium salts to build their
  shells. They remove salt from the water.
• In warm ocean areas where there is little
  rainfall and much evaporation, the amount of
  dissolved salts is much greater. In polar
  regions, the salinity levels are high because
  temperatures are cold enough for ocean water to
  freeze. Pure water is removed and salts are left
  behind.

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Gases in Ocean Water

• The most abundant gases in ocean water are
  nitrogen, carbon dioxide and oxygen.
• The amounts of these elements vary with depth.
  They are more abundant at the oceans surface
  where sunlight causes more plant life.

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Temperature of Ocean Water

• Warm water holds less dissolved gas than cold
  water.
• When ocean water is cold, like in polar regions,
  it sinks and carries oxygen rich water to the
  ocean depths.
• As a result, fish and other animals can live in
  deep parts of the ocean.

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Temperature of Ocean Water

• Sun is the major source of heat for the ocean.
• Motions of the ocean, such as waves and currents,
  mix the surface water and transfer the heat
  downward.

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Surface Zone

• The zone where the water is mixed by waves and
  currents is called the surface zone.
• The surface zone extends 100-400 meters downward.
• The temperature remains constant with depth.
• Temperature in a surface zone changes due to
  seasons and locations.

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Thermocline

• The zone of rapid temperature change is called
  the thermocline.
• The thermocline does not occur at a certain
  depth.
• The season and flow of ocean currents alter the
  depth of the thermocline.
• The thermocline exists because warm, surface
  water does not mix easily with colder, denser
  water.

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Deep Zone

• The thermocline forms a transition between the
  surface zone and the deep zone.
• The deep zone is an area of extremely cold water
  that extends from the bottom of the thermocline
  to depths of 4000 meters or more.

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Deep Zone

• Within the deep zone, temperatures decrease only
  slightly.
• At depths greater than 1500 meters, the
  temperature is about 4 degrees C.
• The three ocean zones are not found in the polar
  (Arctic and Antarctica) regions since the surface
  waters are always cold.

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The Ocean Floor

• The topography of the ocean floor is different
  from the topography of the continents

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The Ocean Floor

• The ocean floor has higher mountains, deeper
  canyons, and larger flatter plains. Earthquakes
  occur more often.
• The rocks are very different.
• The crust is thinner.

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Edges of the Continents

• The shoreline is a boundary between where the
  land and the ocean meet.
• The area where the underwater edge meets of a
  continent meets the ocean floor is called a
  continental margin.

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Continental Margin

• The area where the underwater edge of a continent
  meets the ocean floor is called a continental
  margin.
• A continental margin consists of a continental
  shelf, a continental slope and a continental rise.

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Continental Shelf

• The flat part of a continental margin that is
  covered by shallow ocean water is called a
  continental shelf.
• A continental shelf slopes gently from the
  shoreline.
• The width of the continental shelf varies.
• Large mineral, oil and natural gas deposits are
  found here.

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Continental Slope

• At the edge of the continental shelf, the ocean
  floor plunges steeply 4 to 5 kilometers.
• A continental slope marks the boundary between
  the crust of the continent and the crust of the
  ocean floor.

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Continental Rise

• Separating a continental slope from the ocean
  floor is a continental rise.
• A continental rise is made of large amount of
  sediments, rocks, plants and animals.
• Sometimes the sediments are carried down the
  slope in masses of flowing water called turbidity
  currents, like an underwater avalanche.

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Submarine Canyons

• In many areas, submarine canyons cut through a
  continental shelf and slope.
• They are deep, V-shaped valleys that have been
  cut in the rock, possibly by turbidity currents.
• The Monterey Submarine Canyon(2000 meters) is
  deeper than the Grand Canyon.

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Abyssal Plains

• Large, flat areas on the ocean floor are called
  abyssal plains.
• The abyssal plains are larger in the Atlantic and
  Indian than in the Pacific due to the deposition
  of sediments by large rivers.
• The Pacific Ocean has large cracks that trap
  sediments and result in smaller abyssal plains.

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Abyssal Plains

• Abyssal plains close to the continent are made of
  mud, sand and silt.
• Farther out on the abyssal plains, some of them
  contain the remains of tiny organisms that form
  ooze.
• Where ocean life is not abundant, the floor of
  the ocean is covered with red clay

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Seamounts and Guyots

• Seamounts are underwater volcanic mountains that
  rise more than 100 meters above the ocean floor.
  Most have been found in the Pacific Ocean.
• Some seamounts reach above the surface of the
  water to form islands, like the Azores in the
  Atlantic and the Hawaiian islands in the Pacific.
• Guyots are flat-topped seamounts.

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Trenches

• Trenches are the deepest parts of the ocean found
  along the edge of the ocean floor.
• The Mariana Trench in the Pacific Ocean contains
  the deepest spot (1100 meters) on Earth known as
  Challenger Deep.

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Midocean Ridges

• The midocean ridges form an almost continuous
  mountain belt that extends from the Arctic Ocean
  down through the middle of the Atlantic Ocean
  around Africa into the Indian Ocean and across
  the Pacific Ocean.
• In the Atlantic it is called the mid-Atlantic
  Ridge and in the Pacific, the Pacific-Antarctica
  Ridge.

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Formation of Midocean Ridges

• Mountain ranges on land are formed when the
  Earths crust folds and is squeezed together.
• Midocean ridges are areas where molten material
  from deep within the Earth flows up to the
  surface and cools and forms new crust.

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Rifts

• Running along the middle of the midocean ridges
  between the rows of parallel mountains are deep
  crevices or rifts.
• Rifts are areas of great earthquake and volcanic
  activity.

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Reefs

• Surrounding volcanic islands in tropical waters
  are large masses and ridges of limestone rock,
  known as coral reefs.
• The limestone structures contain the shells of
  animals. These animals cannot exist in water
  cooler than 18 degrees C and deeper than 55
  meters.

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Types of Coral Reefs

• Fringing reefs
• Barrier reefs
• Atoll

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Fringing Reefs

• Fringing reefs are coral reefs that touch the
  shoreline of a volcanic island.
• Fringing reefs are usually less than 30 meters.

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Barrier Reefs

• Barrier reefs are separated from the shore by an
  area of shallow water called a lagoon.
• Barrier reefs are usually larger than fringing
  reefs and surround islands that are more
  submerged.
• The largest barrier reef is the Great Barrier
  Reef of Australia. It is 23oo km long and 320 km
  wide.

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Atoll

• An atoll is a ring of coral reefs that that
  surround an island that has sunk beneath the
  surface of the ocean.

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Ocean Life Zones

• Intertidal Zone (Splash Zone)
• Neritic Zone (Continental Shelf)
• Open Sea Zone
• Bathyal (Continental Slope)
• Abyssal (Ocean floor)

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Ocean Life Zones

• The plant and animal life in the ocean is
  affected by several factors.
• One factor is the amount of sunlight that
  penetrates the ocean.
• Another factor is the temperature of the ocean
  water.
• Water pressure is also a factor.

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Major Groups of Ocean Life

• Plants and animals in the ocean are classified
  into three major groups based on their habits and
  the depth of the water in which they live.
• The three major groups are plankton, nekton and
  benthos.

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Plankton

• Plankton float at or near the surface where
  sunlight can penetrate.
• Most of the plankton are very small, such as
  algae.
• These organisms drift with the currents or tides.
• Plankton are the main food for many larger
  organisms. They account for most of the organisms
  in the ocean.

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Nekton

• Whales , seals , dolphins, squid octopuses,
  barracuda and other fish are all nekton.
• Nekton are free-swimming organisms that feed on
  other nekton as well as on plankton.
• Many have adaptations enabling them to function
  at depths that have great pressure and no light.

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Benthos

• Organisms that live on the ocean floor are
  benthos.
• The forms of these animals include crustaceans
  and shell fish.
• The deep bottom environments are sparsely
  populated with benthos.
• Some benthos are plants that live on the ocean
  floor in shallow waters where sun can penetrate.

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Ocean Life Zones

• The classification of the ocean into life zones
  is based on the conditions in the ocean. These
  conditions vary widely.
• The classification includes the intertidal zone,
  the neritic zone and open-ocean zones.

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Intertidal (Splash) Zone

• This region is the most changeable in the ocean.
• Anemones, crabs, clams, mussels and plants such
  as seaweed live here.
• They must be able to exist without water for
  periods of time.
• They must be able to anchor to keep from being
  washed out to sea.

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Neritic ( Shelf) Zone

• This zone extends to a depth of 200 meters and
  receives plenty of sunlight.
• The water pressure is low and the temperature is
  constant.
• This zone can support plankton, nekton and
  benthos.
• Marine life is most abundant here.

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Open Ocean Zones

• There are two open-ocean zonesbathyal and
  abyssal

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Bathyal (Slope)

• The bathyal zone begins at the continental slope
  and extends down about 2000 meters.
• Sunlight cannot penetrate the bottom of this zone
  and plants do not grow at the bottom.
• Many forms of nekton, such as squid, octopus and
  large whales live in this zone.

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Abyssal (Ocean Floor) Zone

• At a depth of about 2000 meters, the abyssal zone
  begins.
• The abyssal zone extends to a depth of 6000
  meters.
• This zone covers the large flat plains of the
  ocean. No sunlight can penetrate and food is
  scarce. The water pressure is great.
• Most of the animals here are small.
• Some make their own light.

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Studying the Ocean Floor

• In 1872, the first expedition to explore the
  ocean began when the Challenger sailed from
  England.
• Scientists used wire to measure the ocean depth.
• Scientists aboard used nets to collect animals
  and plants from the ocean floor.
• Special thermometers measured the temperature.
  Samples of water were collected.

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Present Oceanographers

• Today oceanographers have modern instruments.
• Underwater cameras provide pictures of the ocean
  floor. Corers bring up samples of med and sand
  from the ocean bottom.
• Bathyspheres, bathscaphs and other submersibles
  are able to dive deep under the surface to explore

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Mapping the Ocean Floor

• One of the most important goals is to map the
  ocean floor. This is done by indirect methods
  such as echo sounding, radar, sonar and
  seismographic surveys.

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Echo Soundings

• All of these methods are based on the same
  principles. Energy waves are sent down to the
  floor are reflected and return to the surface,
  where they are recorded.
• Knowing the speed of sound, 1500 m per second,
  oceanographers can determine the depth.
• The most complete picture was gathered from
  information from a satellite, the Seasat,
  launched in 1978

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Motions of the Oceans

• Ocean water never stops moving.
• The three basic motions of the ocean are the
  up and down movement of the waves. The steady
  movement of ocean currents and the rise and fall
  of the ocean tides.

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Waves

• Waves are pulses of energy that move through the
  ocean.
• Waves are set in motion by winds, earthquakes and
  the gravitational pull of the moon.
• The most common source of wave movement is the
  wind blowing across the surface.

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Movement of Waves

• The water in a wave is not moving forward at all.
  Only the energy moves forward through the water
  producing one wave after another.
• The energy is passed from particle to particle.
  It is also passed downward. With increasing
  depth, the motion of the particles decrease. At
  a certain depth the motion stops. In deep water,
  there are no waves except those caused by tides
  and earthquakes.

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Height of the Waves

• Three factors affect the height of waves wind
  speed, the length of time the wind blows and the
  distance the wind blows over the water.
• As each of these factors increases, the height of
  the wave increases.

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Wave Characteristics

• The point of the wave is called the crest.
• The lowest point of the wave is called the
  trough.
• The horizontal distance between two consecutive
  crests or troughs is the wavelength.
• The vertical distance between a crest and a
  trough is called the wave height.

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Wave Period and Frequency

• The amount of time it takes consecutive crests
  or troughs to pass is called the wave period.
• The number of crests or troughs passing a given
  point in a certain wave period is called the wave
  frequency.
• As wave frequency increases, wave length
  decreases.

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Swells

• Waves stay the same distant apart out in the open
  ocean. The wavelength is constant. These waves
  are called swells.

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Surf

• Waves change as they near the shore. They slow
  down and get closer together. Their wavelength
  decreases and their increase until they crash
  forward as breakers. This is called the surf.

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Undertow

• The water then flows back toward the ocean
  carrying bits of seaweeed, sand and pebbles. The
  retreating water is called an undertow.

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Tsunamis

• Some ocean waves are caused by earthquakes.
• Tsunamis have very long wavelengths and are very
  deep.
• They carry a huge amount of energy Which is
  concentrated in much less water as it nears the
  shore.
• Tsunamis reach heights of 35 meters (an average
  10-story building).

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Currents

• Water below the surface moves in streams called
  currents.
• Currents are caused by two factors wind patterns
  and differences in water density.

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Surface Currents

• Currents caused mainly by wind patterns are
  called surface currents. These currents have a
  depth of several hundred meters.
• The temperature of a current depends on where it
  originated, making it either warm or cold.

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Long-Distance Currents

• Surface currents that travel thousands of
  kilometers are called long-distance currents,
  such as the Gulf Steam.
• The Gulf Stream carries warm water from the
  southern tip of Florida north along the eastern
  coast of the United States moving at speeds of
  1.5 meters per second.

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Continuous Currents

• All currents form a continuous worldwide pattern
  of water circulation.
• The water in each ocean moves in a large, almost
  circular pattern.
• In the Northern Hemisphere, the currents move
  clockwise.
• In the Southern hemisphere, the currents move
  counterclockwise.

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Short- Distance Currents

• Short distance currents are usually found near a
  shoreline where the waves hit at an angle.
• When the waves hit the shoreline, the water turns
  and produces currents that move parallel to the
  shoreline called longshore currents. Longshore
  currents move large quantities of sand which
  deposit in sand bars.

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Rip Current

• If the longshore current cuts an opening in the
  sandbar the water will return to ocean in a
  powerful narrow flow called a rip current.
• A rip current is a type of undertow.

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Deep Currents

• Deep currents are caused mainly by differences in
  water density.
• The cold, salty water, that is more dense,
  flowing from the polar regions moves under the
  less dense water away from the polar regions.
• Most deep currents flow in the opposite direction
  from surface currents.

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Upwellings

• The densest water on Earth lies off the coast of
  Antarctica.
• This water sinks to the ocean floor and flows
  north. As the Antarctic currents come close to
  land, the ocean floor rises, forcing these cold
  currents upward.
• These risings, called upwellings, carry rich food
  from the ocean floor that results in rich fishing
  grounds near PSpring and Neap Tides
• Spring Tides, higher than normal high tides, are
  produced when the sun, Earth and moon line up or
  new and full moon phases.
• Neap tides, lower than normal high tides, are
  produced when the sun, Earth and moon are at
  right angles or first and last quarter moon
  phases.