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The World’s OceansThe World’s Oceans
71% of the Earth’s surface is covered 71% of the Earth’s surface is covered by ocean water.by ocean water.
The oceans contain 97% of the The oceans contain 97% of the earth’s water.earth’s water.
All the oceans and seas are actually All the oceans and seas are actually one continuous body of water.one continuous body of water.
OceansOceans
The oceans are the Atlantic, Pacific, The oceans are the Atlantic, Pacific, Indian. Arctic and Southern.Indian. Arctic and Southern.
The Pacific Ocean is the largest The Pacific Ocean is the largest ocean.ocean.
The area and volume of the Pacific The area and volume of the Pacific Ocean are greater than the Atlantic Ocean are greater than the Atlantic and Indian combined.and Indian combined.
SeasSeas
A sea is a part of an ocean that is A sea is a part of an ocean that is nearly surrounded by water.nearly surrounded by water.
The Mediterranean, Arctic and Black The Mediterranean, Arctic and Black Sea are really part of the Atlantic Sea are really part of the Atlantic Ocean.Ocean.
Water CycleWater Cycle
The sun’s rays heat The sun’s rays heat the surface of the the surface of the ocean.ocean.
The heat causes the The heat causes the water to evaporate.water to evaporate.
The evaporating water The evaporating water (clean, fresh water) (clean, fresh water) enters the atmosphere enters the atmosphere as water vapor.as water vapor.
The salt remains The salt remains behind.behind.
Water CycleWater Cycle
Winds carry water Winds carry water vapor over land.vapor over land.
Some of the water Some of the water vapor condenses to vapor condenses to form clouds.form clouds.
The water in the The water in the clouds falls as clouds falls as precipitation.precipitation.
Water CycleWater Cycle
Some of this water Some of this water runs into rivers and runs into rivers and streams which flow streams which flow back into the back into the oceans.oceans.
Some of the water Some of the water seeps into the soil seeps into the soil and rocks become and rocks become part of the part of the groundwater.groundwater.
Properties of Ocean WaterProperties of Ocean Water
Ocean water is a mixture of gases Ocean water is a mixture of gases and solids dissolved in pure water.and solids dissolved in pure water.
Oceanographers believe oceans Oceanographers believe oceans contain all the natural elements on contain all the natural elements on Earth.Earth.
85 of 90 have been found in the 85 of 90 have been found in the ocean.ocean.
Major Elements in the OceanMajor Elements in the Ocean
Ocean water is 96% pure water.Ocean water is 96% pure water. Chlorine (1.9) and sodium (1.1) make Chlorine (1.9) and sodium (1.1) make
up the next largest concentration of up the next largest concentration of elements.elements.
Sodium chloride is table salt.Sodium chloride is table salt.
SalinitySalinity
Salinity describes the amount of Salinity describes the amount of dissolved water in the ocean.dissolved water in the ocean.
Salinity is expressed in parts per Salinity is expressed in parts per thousand.thousand.
The salinity level of the ocean is The salinity level of the ocean is expressed in parts per thousand. expressed in parts per thousand.
The average salinity of ocean is 35 The average salinity of ocean is 35 parts per thousand.parts per thousand.
Sources of Salt in the OceanSources of Salt in the Ocean
When volcanoes erupt, rock When volcanoes erupt, rock materials and gases, such as materials and gases, such as chlorine, spew forth.chlorine, spew forth.
As rivers, streams and glaciers move As rivers, streams and glaciers move over rock and soil, they dissolve over rock and soil, they dissolve salts, such as magnesium, sodium salts, such as magnesium, sodium and potassium, in them.and potassium, in them.
As waves pound the shoreline, they As waves pound the shoreline, they dissolve salts from the rocks.dissolve salts from the rocks.
Salinity LevelsSalinity Levels The salinity is lower in areas where freshwater The salinity is lower in areas where freshwater
rivers run into the ocean. Salinity levels are also rivers run into the ocean. Salinity levels are also affected by animals such as clams and oysters affected by animals such as clams and oysters that use calcium salts to build their shells. They that use calcium salts to build their shells. They remove salt from the water.remove salt from the water.
In warm ocean areas where there is little rainfall In warm ocean areas where there is little rainfall and much evaporation, the amount of dissolved and much evaporation, the amount of dissolved salts is much greater. In polar regions, the salts is much greater. In polar regions, the salinity levels are high because temperatures are salinity levels are high because temperatures are cold enough for ocean water to freeze. Pure water cold enough for ocean water to freeze. Pure water is removed and salts are left behind.is removed and salts are left behind.
Gases in Ocean WaterGases in Ocean Water
The most abundant gases in ocean The most abundant gases in ocean water are nitrogen, carbon dioxide water are nitrogen, carbon dioxide and oxygen.and oxygen.
The amounts of these elements vary The amounts of these elements vary with depth. They are more abundant with depth. They are more abundant at the ocean’s surface where sunlight at the ocean’s surface where sunlight causes more plant life.causes more plant life.
Temperature of Ocean WaterTemperature of Ocean Water
Warm water holds less dissolved gas Warm water holds less dissolved gas than cold water.than cold water.
When ocean water is cold, like in When ocean water is cold, like in polar regions, it sinks and carries polar regions, it sinks and carries oxygen rich water to the ocean oxygen rich water to the ocean depths.depths.
As a result, fish and other animals As a result, fish and other animals can live in deep parts of the ocean.can live in deep parts of the ocean.
Temperature of Ocean WaterTemperature of Ocean Water
Sun is the major Sun is the major source of heat for source of heat for the ocean.the ocean.
Motions of the Motions of the ocean, such as ocean, such as waves and waves and currents, mix the currents, mix the surface water and surface water and transfer the heat transfer the heat downward.downward.
Surface ZoneSurface Zone
The zone where the water is mixed by The zone where the water is mixed by waves and currents is called the surface waves and currents is called the surface zone.zone.
The surface zone extends 100-400 meters The surface zone extends 100-400 meters downward.downward.
The temperature remains constant with The temperature remains constant with depth.depth.
Temperature in a surface zone changes Temperature in a surface zone changes due to seasons and locations.due to seasons and locations.
ThermoclineThermocline
The zone of rapid temperature change is The zone of rapid temperature change is called the thermocline. called the thermocline.
The thermocline does not occur at a The thermocline does not occur at a certain depth.certain depth.
The season and flow of ocean currents The season and flow of ocean currents alter the depth of the thermocline.alter the depth of the thermocline.
The thermocline exists because warm, The thermocline exists because warm, surface water does not mix easily with surface water does not mix easily with colder, denser water.colder, denser water.
Deep ZoneDeep Zone
The thermocline forms a transition The thermocline forms a transition between the surface zone and the between the surface zone and the deep zone.deep zone.
The deep zone is an area of The deep zone is an area of extremely cold water that extends extremely cold water that extends from the bottom of the thermocline from the bottom of the thermocline to depths of 4000 meters or more.to depths of 4000 meters or more.
Deep ZoneDeep Zone
Within the deep zone, temperatures Within the deep zone, temperatures decrease only slightly.decrease only slightly.
At depths greater than 1500 meters, At depths greater than 1500 meters, the temperature is about 4 degrees the temperature is about 4 degrees C.C.
The three ocean zones are not found The three ocean zones are not found in the polar (Arctic and Antarctica) in the polar (Arctic and Antarctica) regions since the surface waters are regions since the surface waters are always cold.always cold.
The Ocean FloorThe Ocean Floor
The topography of the ocean floor is The topography of the ocean floor is different from the topography of the different from the topography of the continentscontinents
The Ocean FloorThe Ocean Floor
The ocean floor has higher mountains, The ocean floor has higher mountains, deeper canyons, and larger flatter plains. deeper canyons, and larger flatter plains. Earthquakes occur more often.Earthquakes occur more often.
The rocks are very different.The rocks are very different. The crust is thinner.The crust is thinner.
Edges of the ContinentsEdges of the Continents
The shoreline is a boundary between The shoreline is a boundary between where the land and the ocean meet.where the land and the ocean meet.
The area where the underwater edge The area where the underwater edge meets of a continent meets the ocean meets of a continent meets the ocean floor is called a continental margin.floor is called a continental margin.
Continental MarginContinental Margin
The area where the underwater edge The area where the underwater edge of a continent meets the ocean floor of a continent meets the ocean floor is called a continental margin.is called a continental margin.
A continental margin consists of a A continental margin consists of a continental shelf, a continental slope continental shelf, a continental slope and a continental rise.and a continental rise.
Continental ShelfContinental Shelf
The flat part of a continental margin The flat part of a continental margin that is covered by shallow ocean that is covered by shallow ocean water is called a continental shelf.water is called a continental shelf.
A continental shelf slopes gently A continental shelf slopes gently from the shoreline.from the shoreline.
The width of the continental shelf The width of the continental shelf varies.varies.
Large mineral, oil and natural gas Large mineral, oil and natural gas deposits are found here.deposits are found here.
Continental SlopeContinental Slope
At the edge of the continental shelf, At the edge of the continental shelf, the ocean floor plunges steeply 4 to the ocean floor plunges steeply 4 to 5 kilometers.5 kilometers.
A continental slope marks the A continental slope marks the boundary between the crust of the boundary between the crust of the continent and the crust of the ocean continent and the crust of the ocean floor.floor.
Continental RiseContinental Rise
Separating a continental slope from Separating a continental slope from the ocean floor is a continental rise.the ocean floor is a continental rise.
A continental rise is made of large A continental rise is made of large amount of sediments, rocks, plants amount of sediments, rocks, plants and animals. and animals.
Sometimes the sediments are carried Sometimes the sediments are carried down the slope in masses of flowing down the slope in masses of flowing water called turbidity currents, like water called turbidity currents, like an underwater avalanche.an underwater avalanche.
Submarine CanyonsSubmarine Canyons
In many areas, submarine canyons In many areas, submarine canyons cut through a continental shelf and cut through a continental shelf and slope.slope.
They are deep, V-shaped valleys that They are deep, V-shaped valleys that have been cut in the rock, possibly have been cut in the rock, possibly by turbidity currents.by turbidity currents.
The Monterey Submarine The Monterey Submarine Canyon(2000 meters) is deeper than Canyon(2000 meters) is deeper than the Grand Canyon.the Grand Canyon.
Abyssal PlainsAbyssal Plains
Large, flat areas on the ocean floor Large, flat areas on the ocean floor are called abyssal plains.are called abyssal plains.
The abyssal plains are larger in the The abyssal plains are larger in the Atlantic and Indian than in the Pacific Atlantic and Indian than in the Pacific due to the deposition of sediments due to the deposition of sediments by large rivers.by large rivers.
The Pacific Ocean has large cracks The Pacific Ocean has large cracks that trap sediments and result in that trap sediments and result in smaller abyssal plains.smaller abyssal plains.
Abyssal PlainsAbyssal Plains
Abyssal plains close to the continent Abyssal plains close to the continent are made of mud, sand and silt.are made of mud, sand and silt.
Farther out on the abyssal plains, Farther out on the abyssal plains, some of them contain the remains of some of them contain the remains of tiny organisms that form ooze.tiny organisms that form ooze.
Where ocean life is not abundant, the Where ocean life is not abundant, the floor of the ocean is covered with red floor of the ocean is covered with red clayclay
Seamounts and GuyotsSeamounts and Guyots
Seamounts are underwater volcanic Seamounts are underwater volcanic mountains that rise more than 100 meters mountains that rise more than 100 meters above the ocean floor. Most have been above the ocean floor. Most have been found in the Pacific Ocean.found in the Pacific Ocean.
Some seamounts reach above the surface Some seamounts reach above the surface of the water to form islands, like the of the water to form islands, like the Azores in the Atlantic and the Hawaiian Azores in the Atlantic and the Hawaiian islands in the Pacific.islands in the Pacific.
Guyots are flat-topped seamounts.Guyots are flat-topped seamounts.
TrenchesTrenches
Trenches are the deepest parts of Trenches are the deepest parts of the ocean found along the edge of the ocean found along the edge of the ocean floor.the ocean floor.
The Mariana Trench in the Pacific The Mariana Trench in the Pacific Ocean contains the deepest spot Ocean contains the deepest spot (1100 meters) on Earth known as (1100 meters) on Earth known as Challenger Deep.Challenger Deep.
Midocean RidgesMidocean Ridges
The midocean ridges form an almost The midocean ridges form an almost continuous mountain belt that continuous mountain belt that extends from the Arctic Ocean down extends from the Arctic Ocean down through the middle of the Atlantic through the middle of the Atlantic Ocean around Africa into the Indian Ocean around Africa into the Indian Ocean and across the Pacific Ocean.Ocean and across the Pacific Ocean.
In the Atlantic it is called the mid-In the Atlantic it is called the mid-Atlantic Ridge and in the Pacific, the Atlantic Ridge and in the Pacific, the Pacific-Antarctica Ridge.Pacific-Antarctica Ridge.
Formation of Midocean RidgesFormation of Midocean Ridges
Mountain ranges on land are formed Mountain ranges on land are formed when the Earth’s crust folds and is when the Earth’s crust folds and is squeezed together.squeezed together.
Midocean ridges are areas where Midocean ridges are areas where molten material from deep within the molten material from deep within the Earth flows up to the surface and Earth flows up to the surface and cools and forms new crust.cools and forms new crust.
RiftsRifts
Running along the middle of the Running along the middle of the midocean ridges between the rows of midocean ridges between the rows of parallel mountains are deep crevices parallel mountains are deep crevices or rifts.or rifts.
Rifts are areas of great earthquake Rifts are areas of great earthquake and volcanic activity.and volcanic activity.
ReefsReefs
Surrounding volcanic islands in Surrounding volcanic islands in tropical waters are large masses and tropical waters are large masses and ridges of limestone rock, known as ridges of limestone rock, known as coral reefs.coral reefs.
The limestone structures contain the The limestone structures contain the shells of animals. These animals shells of animals. These animals cannot exist in water cooler than 18 cannot exist in water cooler than 18 degrees C and deeper than 55 degrees C and deeper than 55 meters.meters.
Types of Coral ReefsTypes of Coral Reefs
Fringing reefsFringing reefs Barrier reefsBarrier reefs AtollAtoll
Fringing ReefsFringing Reefs
Fringing reefs are coral reefs that Fringing reefs are coral reefs that touch the shoreline of a volcanic touch the shoreline of a volcanic island.island.
Fringing reefs are usually less than Fringing reefs are usually less than 30 meters.30 meters.
Barrier ReefsBarrier Reefs
Barrier reefs are separated from the Barrier reefs are separated from the shore by an area of shallow water shore by an area of shallow water called a lagoon. called a lagoon.
Barrier reefs are usually larger than Barrier reefs are usually larger than fringing reefs and surround islands fringing reefs and surround islands that are more submerged.that are more submerged.
The largest barrier reef is the Great The largest barrier reef is the Great Barrier Reef of Australia. It is 23oo Barrier Reef of Australia. It is 23oo km long and 320 km wide.km long and 320 km wide.
AtollAtoll
An atoll is a ring of coral reefs that An atoll is a ring of coral reefs that that surround an island that has sunk that surround an island that has sunk beneath the surface of the ocean.beneath the surface of the ocean.
Ocean Life ZonesOcean Life Zones
Intertidal Zone (Splash Zone)Intertidal Zone (Splash Zone) Neritic Zone (Continental Shelf)Neritic Zone (Continental Shelf) Open Sea Zone –Open Sea Zone – Bathyal (Continental Slope) Bathyal (Continental Slope) Abyssal (Ocean floor)Abyssal (Ocean floor)
Ocean Life ZonesOcean Life Zones
The plant and animal life in the The plant and animal life in the ocean is affected by several factors.ocean is affected by several factors.
One factor is the amount of sunlight One factor is the amount of sunlight that penetrates the ocean.that penetrates the ocean.
Another factor is the temperature of Another factor is the temperature of the ocean water.the ocean water.
Water pressure is also a factor.Water pressure is also a factor.
Major Groups of Ocean LifeMajor Groups of Ocean Life
Plants and animals in the ocean are Plants and animals in the ocean are classified into three major groups classified into three major groups based on their habits and the depth based on their habits and the depth of the water in which they live.of the water in which they live.
The three major groups are plankton, The three major groups are plankton, nekton and benthos.nekton and benthos.
PlanktonPlankton
Plankton float at or near the surface Plankton float at or near the surface where sunlight can penetrate.where sunlight can penetrate.
Most of the plankton are very small, Most of the plankton are very small, such as algae.such as algae.
These organisms drift with the These organisms drift with the currents or tides.currents or tides.
Plankton are the main food for many Plankton are the main food for many larger organisms. They account for larger organisms. They account for most of the organisms in the ocean.most of the organisms in the ocean.
NektonNekton
Whales , seals , dolphins, squid Whales , seals , dolphins, squid octopuses, barracuda and other fish octopuses, barracuda and other fish are all nekton.are all nekton.
Nekton are free-swimming organisms Nekton are free-swimming organisms that feed on other nekton as well as that feed on other nekton as well as on plankton.on plankton.
Many have adaptations enabling Many have adaptations enabling them to function at depths that have them to function at depths that have great pressure and no light.great pressure and no light.
BenthosBenthos
Organisms that live on the ocean Organisms that live on the ocean floor are benthos.floor are benthos.
The forms of these animals include The forms of these animals include crustaceans and shell fish.crustaceans and shell fish.
The deep bottom environments are The deep bottom environments are sparsely populated with benthos.sparsely populated with benthos.
Some benthos are plants that live on Some benthos are plants that live on the ocean floor in shallow waters the ocean floor in shallow waters where sun can penetrate.where sun can penetrate.
Ocean Life ZonesOcean Life Zones
The classification of the ocean into The classification of the ocean into life zones is based on the conditions life zones is based on the conditions in the ocean. These conditions vary in the ocean. These conditions vary widely.widely.
The classification includes the The classification includes the intertidal zone, the neritic zone and intertidal zone, the neritic zone and open-ocean zones.open-ocean zones.
Intertidal (Splash) ZoneIntertidal (Splash) Zone
This region is the most changeable in This region is the most changeable in the ocean.the ocean.
Anemones, crabs, clams, mussels Anemones, crabs, clams, mussels and plants such as seaweed live and plants such as seaweed live here.here.
They must be able to exist without They must be able to exist without water for periods of time.water for periods of time.
They must be able to anchor to keep They must be able to anchor to keep from being washed out to sea.from being washed out to sea.
Neritic ( Shelf) ZoneNeritic ( Shelf) Zone
This zone extends to a depth of 200 This zone extends to a depth of 200 meters and receives plenty of meters and receives plenty of sunlight.sunlight.
The water pressure is low and the The water pressure is low and the temperature is constant.temperature is constant.
This zone can support plankton, This zone can support plankton, nekton and benthos.nekton and benthos.
Marine life is most abundant here.Marine life is most abundant here.
Open Ocean ZonesOpen Ocean Zones
There are two open-ocean There are two open-ocean zones:bathyal and abyssalzones:bathyal and abyssal
Bathyal (Slope)Bathyal (Slope)
The bathyal zone begins at the The bathyal zone begins at the continental slope and extends down continental slope and extends down about 2000 meters.about 2000 meters.
Sunlight cannot penetrate the Sunlight cannot penetrate the bottom of this zone and plants do not bottom of this zone and plants do not grow at the bottom.grow at the bottom.
Many forms of nekton, such as squid, Many forms of nekton, such as squid, octopus and large whales live in this octopus and large whales live in this zone.zone.
Abyssal (Ocean Floor) ZoneAbyssal (Ocean Floor) Zone
At a depth of about 2000 meters, the At a depth of about 2000 meters, the abyssal zone begins. abyssal zone begins.
The abyssal zone extends to a depth of The abyssal zone extends to a depth of 6000 meters.6000 meters.
This zone covers the large flat plains of the This zone covers the large flat plains of the ocean. No sunlight can penetrate and ocean. No sunlight can penetrate and food is scarce. The water pressure is great.food is scarce. The water pressure is great.
Most of the animals here are small.Most of the animals here are small. Some make their own light.Some make their own light.
Studying the Ocean FloorStudying the Ocean Floor
In 1872, the first expedition to explore the In 1872, the first expedition to explore the ocean began when the ocean began when the Challenger Challenger sailed sailed from England.from England.
Scientists used wire to measure the ocean Scientists used wire to measure the ocean depth.depth.
Scientists aboard used nets to collect Scientists aboard used nets to collect animals and plants from the ocean floor.animals and plants from the ocean floor.
Special thermometers measured the Special thermometers measured the temperature. Samples of water were temperature. Samples of water were collected.collected.
Present OceanographersPresent Oceanographers
Today oceanographers have modern Today oceanographers have modern instruments.instruments.
Underwater cameras provide pictures Underwater cameras provide pictures of the ocean floor. Corers bring up of the ocean floor. Corers bring up samples of med and sand from the samples of med and sand from the ocean bottom. ocean bottom.
Bathyspheres, bathscaphs and other Bathyspheres, bathscaphs and other submersibles are able to dive deep submersibles are able to dive deep under the surface to exploreunder the surface to explore
Mapping the Ocean FloorMapping the Ocean Floor
One of the most important goals is to One of the most important goals is to map the ocean floor. This is done by map the ocean floor. This is done by indirect methods such as echo indirect methods such as echo sounding, radar, sonar and sounding, radar, sonar and seismographic surveys.seismographic surveys.
Echo SoundingsEcho Soundings
All of these methods are based on the All of these methods are based on the same principles. Energy waves are sent same principles. Energy waves are sent down to the floor are reflected and return down to the floor are reflected and return to the surface, where they are recorded.to the surface, where they are recorded.
Knowing the speed of sound, 1500 m per Knowing the speed of sound, 1500 m per second, oceanographers can determine second, oceanographers can determine the depth.the depth.
The most complete picture was gathered The most complete picture was gathered from information from a satellite, the from information from a satellite, the SeasatSeasat, launched in 1978, launched in 1978
Motions of the OceansMotions of the Oceans
Ocean water never stops moving. Ocean water never stops moving. The three basic motions of the ocean The three basic motions of the ocean
are : the up and down movement of are : the up and down movement of the waves. The steady movement of the waves. The steady movement of ocean currents and the rise and fall ocean currents and the rise and fall of the ocean tides.of the ocean tides.
WavesWaves
Waves are pulses of energy that Waves are pulses of energy that move through the ocean.move through the ocean.
Waves are set in motion by winds, Waves are set in motion by winds, earthquakes and the gravitational earthquakes and the gravitational pull of the moon.pull of the moon.
The most common source of wave The most common source of wave movement is the wind blowing across movement is the wind blowing across the surface.the surface.
Movement of WavesMovement of Waves
The water in a wave is not moving forward The water in a wave is not moving forward at all. Only the energy moves forward at all. Only the energy moves forward through the water producing one wave through the water producing one wave after another.after another.
The energy is passed from particle to The energy is passed from particle to particle. It is also passed downward. With particle. It is also passed downward. With increasing depth, the motion of the increasing depth, the motion of the particles decrease. At a certain depth the particles decrease. At a certain depth the motion stops. In deep water, there are no motion stops. In deep water, there are no waves except those caused by tides and waves except those caused by tides and earthquakes.earthquakes.
Height of the WavesHeight of the Waves
Three factors affect the height of Three factors affect the height of waves: wind speed, the length of waves: wind speed, the length of time the wind blows and the distance time the wind blows and the distance the wind blows over the water.the wind blows over the water.
As each of these factors increases, As each of these factors increases, the height of the wave increases.the height of the wave increases.
Wave CharacteristicsWave Characteristics
The point of the wave is called the crest.The point of the wave is called the crest. The lowest point of the wave is called the The lowest point of the wave is called the
trough.trough. The horizontal distance between two The horizontal distance between two
consecutive crests or troughs is the consecutive crests or troughs is the wavelength.wavelength.
The vertical distance between a crest and The vertical distance between a crest and a trough is called the wave height.a trough is called the wave height.
Wave Period and FrequencyWave Period and Frequency
The amount of time it takes The amount of time it takes consecutive crests or troughs to pass consecutive crests or troughs to pass is called the wave period.is called the wave period.
The number of crests or troughs The number of crests or troughs passing a given point in a certain passing a given point in a certain wave period is called the wave wave period is called the wave frequency.frequency.
As wave frequency increases, wave As wave frequency increases, wave length decreases.length decreases.
SwellsSwells
Waves stay the same distant apart Waves stay the same distant apart out in the open ocean. The out in the open ocean. The wavelength is constant. These wavelength is constant. These waves are called swells.waves are called swells.
SurfSurf
Waves change as they near the Waves change as they near the shore. They slow down and get shore. They slow down and get closer together. Their wavelength closer together. Their wavelength decreases and their increase until decreases and their increase until they crash forward as breakers. This they crash forward as breakers. This is called the surf.is called the surf.
UndertowUndertow
The water then flows back toward The water then flows back toward the ocean carrying bits of seaweeed, the ocean carrying bits of seaweeed, sand and pebbles. The retreating sand and pebbles. The retreating water is called an undertow.water is called an undertow.
TsunamisTsunamis
Some ocean waves are caused by Some ocean waves are caused by earthquakes.earthquakes.
Tsunamis have very long Tsunamis have very long wavelengths and are very deep.wavelengths and are very deep.
They carry a huge amount of energy They carry a huge amount of energy Which is concentrated in much less Which is concentrated in much less water as it nears the shore.water as it nears the shore.
Tsunamis reach heights of 35 meters Tsunamis reach heights of 35 meters (an average 10-story building).(an average 10-story building).
CurrentsCurrents
Water below the surface moves in Water below the surface moves in streams called currents.streams called currents.
Currents are caused by two factors: Currents are caused by two factors: wind patterns and differences in wind patterns and differences in water density.water density.
Surface CurrentsSurface Currents
Currents caused mainly by wind Currents caused mainly by wind patterns are called surface currents. patterns are called surface currents. These currents have a depth of These currents have a depth of several hundred meters.several hundred meters.
The temperature of a current The temperature of a current depends on where it originated, depends on where it originated, making it either warm or cold.making it either warm or cold.
Long-Distance CurrentsLong-Distance Currents
Surface currents that travel Surface currents that travel thousands of kilometers are called thousands of kilometers are called long-distance currents, such as the long-distance currents, such as the Gulf Steam.Gulf Steam.
The Gulf Stream carries warm water The Gulf Stream carries warm water from the southern tip of Florida north from the southern tip of Florida north along the eastern coast of the United along the eastern coast of the United States moving at speeds of 1.5 States moving at speeds of 1.5 meters per second.meters per second.
Continuous CurrentsContinuous Currents
All currents form a continuous All currents form a continuous worldwide pattern of water worldwide pattern of water circulation.circulation.
The water in each ocean moves in a The water in each ocean moves in a large, almost circular pattern.large, almost circular pattern.
In the Northern Hemisphere, the In the Northern Hemisphere, the currents move clockwise. currents move clockwise.
In the Southern hemisphere, the In the Southern hemisphere, the currents move counterclockwise.currents move counterclockwise.
Short- Distance CurrentsShort- Distance Currents
Short distance currents are usually found Short distance currents are usually found near a shoreline where the waves hit at an near a shoreline where the waves hit at an angle.angle.
When the waves hit the shoreline, the When the waves hit the shoreline, the water turns and produces currents that water turns and produces currents that move parallel to the shoreline called move parallel to the shoreline called longshore currents. Longshore currents longshore currents. Longshore currents move large quantities of sand which move large quantities of sand which deposit in sand bars.deposit in sand bars.
Rip CurrentRip Current
If the longshore current cuts an If the longshore current cuts an opening in the sandbar the water will opening in the sandbar the water will return to ocean in a powerful narrow return to ocean in a powerful narrow flow called a rip current.flow called a rip current.
A rip current is a type of undertow.A rip current is a type of undertow.
Deep CurrentsDeep Currents
Deep currents are caused mainly by Deep currents are caused mainly by differences in water density.differences in water density.
The cold, salty water, that is more The cold, salty water, that is more dense, flowing from the polar regions dense, flowing from the polar regions moves under the less dense water moves under the less dense water away from the polar regions.away from the polar regions.
Most deep currents flow in the Most deep currents flow in the opposite direction from surface opposite direction from surface currents.currents.
UpwellingsUpwellings The densest water on Earth lies off the coast of Antarctica.The densest water on Earth lies off the coast of Antarctica. This water sinks to the ocean floor and flows north. As the This water sinks to the ocean floor and flows north. As the
Antarctic currents come close to land, the ocean floor rises, Antarctic currents come close to land, the ocean floor rises, forcing these cold currents upward.forcing these cold currents upward.
These risings, called upwellings, carry rich food from the These risings, called upwellings, carry rich food from the ocean floor that results in rich fishing grounds near ocean floor that results in rich fishing grounds near PPSpring and Neap TidesSpring and Neap Tides
Spring Tides, higher than normal high tides, are Spring Tides, higher than normal high tides, are produced when the sun, Earth and moon line up or produced when the sun, Earth and moon line up or new and full moon phases.new and full moon phases.
Neap tides, lower than normal high tides, are Neap tides, lower than normal high tides, are produced when the sun, Earth and moon are at produced when the sun, Earth and moon are at right angles or first and last quarter moon phases.right angles or first and last quarter moon phases.
