Oceanography: Oceanography: Mapping the Ocean Mapping the Ocean

FloorFloorOcean Floor TopographyOcean Floor Topography

Why do you think there Why do you think there is less information about is less information about the sea floor than about the sea floor than about

landforms?landforms?

History of Ocean History of Ocean ExplorationExploration In the early 1800’s, mariners recorded depths In the early 1800’s, mariners recorded depths

of shallow water features with a weighted line. of shallow water features with a weighted line. In 1854, a depth-sounding device was attached In 1854, a depth-sounding device was attached

to the line instead of the weight. This made to the line instead of the weight. This made determining when the line hit the bottom of the determining when the line hit the bottom of the ocean floor easier.ocean floor easier.

During WWII, sonar (sound navigation During WWII, sonar (sound navigation ranging) was developed to measure ranging) was developed to measure distance by using a returning echo.distance by using a returning echo.

Today, advanced sonar is being established to Today, advanced sonar is being established to make ocean floor mapping more accurate. make ocean floor mapping more accurate. GLORIA (Geologic Long-Range Inclined GLORIA (Geologic Long-Range Inclined Asdic) is a side-scan sonar device that can Asdic) is a side-scan sonar device that can be towed behind a vessel and can record be towed behind a vessel and can record the depth along the side of the vessel as the depth along the side of the vessel as well as below it.well as below it.

New TechnologyNew Technology Ocean floor sensing technology has grown Ocean floor sensing technology has grown

tremendously since ocean floor mapping started.tremendously since ocean floor mapping started. SatellitesSatellites - a device designed to be - a device designed to be

launched into orbit around the launched into orbit around the Earth, another planet, the sun, etc. Earth, another planet, the sun, etc.

Remote sensingRemote sensing - the science of - the science of gathering data on an object or area gathering data on an object or area from a considerable distance to from a considerable distance to observe the Earth observe the Earth

SonarSonar - a method for detecting and - a method for detecting and locating objects submerged in water locating objects submerged in water by determining the time for an echo by determining the time for an echo to return and the direction from to return and the direction from which it returnswhich it returns

Questions to answerQuestions to answerDirections: Write the following Directions: Write the following

questions leaving space to answer questions leaving space to answer them from the videothem from the video 1- What is the depth of the deepest part of 1- What is the depth of the deepest part of

the ocean? How much deeper is it than the the ocean? How much deeper is it than the Grand Canyon?Grand Canyon?

2- How do scientists travel down to the 2- How do scientists travel down to the ocean floor? ocean floor?

3- What is the top level of the ocean floor 3- What is the top level of the ocean floor called?called?

4- What is the second level of the ocean 4- What is the second level of the ocean floor?floor?

5- What is the third level of the ocean 5- What is the third level of the ocean floor? floor?

Ocean Floor TopographyOcean Floor Topography OceanographyOceanography - is the study of the deep sea and - is the study of the deep sea and

shallow coastal oceansshallow coastal oceans Bathymetric mapsBathymetric maps are topographic maps of the are topographic maps of the

bottom features of a lake, bay, or ocean.bottom features of a lake, bay, or ocean. Bathymetric maps are very similar to Bathymetric maps are very similar to

topographic maps, except that topographic maps, except that bathymetric bathymetric mapsmaps show the show the depth below sea leveldepth below sea level and and topographic mapstopographic maps show the show the elevation above sea elevation above sea levellevel..

Contour LinesContour Lines Topographic maps Topographic maps

and bathymetric and bathymetric maps use contour maps use contour lines to show lines to show elevation or depth. elevation or depth.

The contour interval The contour interval is the difference is the difference between any two between any two contour lines.contour lines. For example, a contour For example, a contour

interval of 100 ft means that interval of 100 ft means that the land or sea bottom has the land or sea bottom has risen or declined by 100 ft.risen or declined by 100 ft.

Underwater LandformsUnderwater Landforms SeamountSeamount – a mountain – a mountain

under the ocean formed under the ocean formed from volcanic activityfrom volcanic activity

TrenchTrench– a long, deep – a long, deep valley where old ocean valley where old ocean floor sinks back toward floor sinks back toward the mantlethe mantle

Abyssal plainAbyssal plain – where the – where the seafloor is shallow along seafloor is shallow along the continentthe continent

Submarine canyonSubmarine canyon – – where rivers empty into where rivers empty into the sea, canyons are cut the sea, canyons are cut into the underwater plaininto the underwater plain

Mid-Ocean ridgeMid-Ocean ridge – a – a series of mountain series of mountain ranges on the ocean floor ranges on the ocean floor extending through all of extending through all of the ocean in the world; the ocean in the world; cause by plate tectonics cause by plate tectonics and seafloor spreadingand seafloor spreading

Why is it important?Why is it important? Ocean floor mapping explained the theory Ocean floor mapping explained the theory

of plate tectonics and sea floor spreadingof plate tectonics and sea floor spreading Scientists learned about magnetic striping Scientists learned about magnetic striping

and polar reversaland polar reversal Helped to explain the occurrence of Helped to explain the occurrence of

earthquakes in certain areas of the worldearthquakes in certain areas of the world Learn about new creatures in the deep – Learn about new creatures in the deep –

possible medical information to be obtainedpossible medical information to be obtained Curiosity about the world around us…Curiosity about the world around us…

Ocean SalinityOcean Salinity

Salinity is the total amount of Salinity is the total amount of dissolved salts in a sample of water. dissolved salts in a sample of water. In most parts of the ocean, the salinity is In most parts of the ocean, the salinity is

between 34 and 37 parts per thousand.between 34 and 37 parts per thousand. Salinity affects ocean water in Salinity affects ocean water in

different ways. different ways. Ocean water does freeze until the Ocean water does freeze until the

temperature drops to about -1.9temperature drops to about -1.900C C whereas freshwater freezes at 0whereas freshwater freezes at 000CC

Saltwater has a higher density than fresh Saltwater has a higher density than fresh waterwater

Ocean Temperature & Ocean Temperature & DepthDepth Like temperatures on land, temperature Like temperatures on land, temperature

at the surface of the ocean vary with at the surface of the ocean vary with location and the seasons. location and the seasons.

Warm water, because it is less dense, forms Warm water, because it is less dense, forms at the ocean surface and does not sink, at the ocean surface and does not sink, therefore cold water is found at lower therefore cold water is found at lower depths.depths.

As you descent through the ocean, the As you descent through the ocean, the water temperature decreases.water temperature decreases.

Surface zone – Avg. temperature is 16.1Surface zone – Avg. temperature is 16.100CC Transition zone – Avg. temperature is about Transition zone – Avg. temperature is about

4400CC Deep zone – Avg. temperature is about 3.5Deep zone – Avg. temperature is about 3.500CC

Surface CurrentsSurface Currents Surface currents affect water to a depth of Surface currents affect water to a depth of

several hundred meters. They are driven several hundred meters. They are driven mainly by winds.mainly by winds. A current is a large stream of moving water A current is a large stream of moving water that flows through the oceans and carries that flows through the oceans and carries water from one place to another.water from one place to another.

Coriolis EffectCoriolis Effect

Currents move in circular patterns Currents move in circular patterns due to the Coriolis effect. In the due to the Coriolis effect. In the northern hemisphere, it causes the northern hemisphere, it causes the currents to curve clockwise; in the currents to curve clockwise; in the southern hemisphere currents move southern hemisphere currents move counterclockwisecounterclockwise

The World’s OceansThe World’s Oceans The Gulf Stream is the largest The Gulf Stream is the largest

and most powerful surface and most powerful surface current in the North Atlantic current in the North Atlantic Ocean caused by strong winds Ocean caused by strong winds from the west.from the west.

Climate is the pattern of Climate is the pattern of temperature and precipitation temperature and precipitation typical over an areas over long typical over an areas over long periods of time. periods of time.

Surface currents warm or cool Surface currents warm or cool the air above it, affect the the air above it, affect the climate of land near the coasts.climate of land near the coasts.

El Nino & La NinaEl Nino & La Nina

El Nino & La NinaEl Nino & La Nina

El Nino – a climate event that occurs El Nino – a climate event that occurs every two to seven years in the every two to seven years in the Pacific Ocean with unusually high Pacific Ocean with unusually high winds and warm ocean waterswinds and warm ocean waters

La Nina – a climate event that brings La Nina – a climate event that brings colder winds and cool ocean waterscolder winds and cool ocean waters

Deep Currents – Global Ocean Deep Currents – Global Ocean ConveyorConveyor Deep currents are caused by differences Deep currents are caused by differences

in the density of ocean water.in the density of ocean water. Deep currents move and mix water Deep currents move and mix water

around the world by carrying cold water around the world by carrying cold water from the poles towards the equator.from the poles towards the equator.

This current is This current is very slow – it very slow – it may take as may take as long as 1,000 long as 1,000 years to years to circulate circulate between the between the oceans and oceans and back where back where they started. they started.