OCEANIC TOPOGRAPHYOCEANIC TOPOGRAPHY

By Greg SchwabBy Greg Schwab

May 7, 2007May 7, 2007

Competency 39Competency 39

• The teacher understands structure The teacher understands structure and function of the hydrosphereand function of the hydrosphere

39.939.9• The beginning teacher identifies the The beginning teacher identifies the

characteristics of different ocean characteristics of different ocean zones (e.g., coastal, lighted, deep, zones (e.g., coastal, lighted, deep, estuaries, bays).estuaries, bays).

TEKS: Geology, Meteorology, TEKS: Geology, Meteorology, OceanographyOceanography

• (11) The student knows characteristics of (11) The student knows characteristics of oceans. The student is expected to:oceans. The student is expected to:

• (11A) Identify physical characteristics of (11A) Identify physical characteristics of ocean water including salinity, heat ocean water including salinity, heat capacity, colligative properties, and capacity, colligative properties, and density.density.

• (11C) Compare the topography of the (11C) Compare the topography of the ocean floor to the topography of the ocean floor to the topography of the continents.continents.

Word WallWord Wall

Continental ShelfContinental Shelf SeamountSeamount

Continental SlopeContinental Slope GuyoutGuyout

Continental RiseContinental Rise AtollAtoll

Oceanic BasinOceanic Basin Volcanic Island Volcanic Island ArcArc

Oceanic RidgesOceanic Ridges BathymetricBathymetric

Oceanic TrenchesOceanic Trenches

Continental ShelfContinental Shelf

A feature of the ocean floor; the A feature of the ocean floor; the flooded margins of the continents flooded margins of the continents that form a zone of relatively shallow that form a zone of relatively shallow water adjacent to the continentswater adjacent to the continents

Characteristics of the shelfCharacteristics of the shelf

• Considered part of the continent not the Considered part of the continent not the oceanocean

• Slopes gently away from land for an Slopes gently away from land for an average of 75km (47 miles)average of 75km (47 miles)

• Average water depth is 130 m (425 ft)Average water depth is 130 m (425 ft)

• Much wider on some parts of the continents Much wider on some parts of the continents than other partsthan other parts

• Retains features of the adjacent land that is Retains features of the adjacent land that is above waterabove water

Continental SlopeContinental Slope

A feature of the ocean floor; a steep A feature of the ocean floor; a steep slope forming the transition between slope forming the transition between the continental shelf and the deep the continental shelf and the deep ocean basin.ocean basin.

Characteristics of the slopeCharacteristics of the slope

• Transition between the continent and Transition between the continent and the deep ocean basinthe deep ocean basin

• Water depth ranges from 120 m (390 ft) Water depth ranges from 120 m (390 ft) to 3,000 m (10,000 ft)to 3,000 m (10,000 ft)

• Width of the slope is 20-40 km (12-25 Width of the slope is 20-40 km (12-25 miles)miles)

• Steeper than the shelfSteeper than the shelf

• Some slopes have submarine canyonsSome slopes have submarine canyons

Submarine CanyonsSubmarine Canyons

• Long deep-sided trenches extending Long deep-sided trenches extending from the top of the slope to the from the top of the slope to the ocean basinocean basin

• Can be similar in size and depth to Can be similar in size and depth to the Grand Canyonthe Grand Canyon

• Believe to been formed by turbidity Believe to been formed by turbidity currents (a muddy current produced currents (a muddy current produced by underwater landslides)by underwater landslides)

Continental RiseContinental Rise

The Transitional area of the The Transitional area of the continental margin between the continental margin between the continental slope and the abyssal continental slope and the abyssal plain.plain.

Characteristics of riseCharacteristics of rise

• Less steep than continental slopeLess steep than continental slope

• Created mainly by sediment deposits Created mainly by sediment deposits from turbidity currents flowing down from turbidity currents flowing down submarine canyons.submarine canyons.

Continental MarginContinental Margin

Composed of the continental shelf, Composed of the continental shelf, continental slope, and continental continental slope, and continental rise.rise.

North American East CoastNorth American East Coast

North American Gulf CoastNorth American Gulf Coast

North American East CoastNorth American East Coast

North American West CoastNorth American West Coast

North American West CoastNorth American West Coast

Ocean BasinOcean Basin

The deep bottom of the ocean floor, The deep bottom of the ocean floor, which starts beyond the continental which starts beyond the continental slope.slope.

Characteristics of the BasinCharacteristics of the Basin

• Deepest part of the ocean floorDeepest part of the ocean floor

• Under 4-6 km (2-4 miles) of seawaterUnder 4-6 km (2-4 miles) of seawater

• Features include: Abyssal plain, Oceanic Features include: Abyssal plain, Oceanic ridges, Oceanic trenches, and Seamountsridges, Oceanic trenches, and Seamounts

• Ocean basin and ridges cover more than Ocean basin and ridges cover more than half the earth’s surfacehalf the earth’s surface

• More surface area than all of the land More surface area than all of the land continentscontinents

Abyssal PlainAbyssal Plain

The practically level plain of the ocean The practically level plain of the ocean basin.basin.

• Covers an area equal to the Covers an area equal to the continental land masscontinental land mass

Oceanic RidgesOceanic Ridges

Long, high, continuous, sub-oceanic Long, high, continuous, sub-oceanic mountain chains; for example, the mountain chains; for example, the Mid-Atlantic Ridge in the center of Mid-Atlantic Ridge in the center of the Atlantic Ocean Basinthe Atlantic Ocean Basin

Characteristics of ridgesCharacteristics of ridges

• Part of a chain of mountains that are Part of a chain of mountains that are 84,000 km long84,000 km long

• Mid-Atlantic Ridge is longest Mid-Atlantic Ridge is longest mountain chain on earthmountain chain on earth

• Ridges are spreading centers or Ridges are spreading centers or divergent plate boundaries where divergent plate boundaries where new ocean floor is creatednew ocean floor is created

Oceanic TrenchesOceanic Trenches

Long, narrow, deep troughs with steep Long, narrow, deep troughs with steep sides that run parallel to the edge of sides that run parallel to the edge of continentscontinents

Characteristics of trenchesCharacteristics of trenches

• Extend 8-11 km below sea levelExtend 8-11 km below sea level

• Long narrow basinsLong narrow basins

• Develop adjacent to subduction Develop adjacent to subduction zoneszones

• Zone of convergenceZone of convergence

• Form parallel to continentsForm parallel to continents

SeamountsSeamounts

Steep submerged volcanic peaks on Steep submerged volcanic peaks on the abyssal plain.the abyssal plain.

Characteristics of Characteristics of seamountsseamounts

• More than 10,000 scatter the ocean More than 10,000 scatter the ocean basinbasin

• By definition rise more than 1 km (0.6 By definition rise more than 1 km (0.6 miles) above the ocean floor.miles) above the ocean floor.

• Can extend above sea level (called an Can extend above sea level (called an island)island)

• Most Pacific Basin islands are Most Pacific Basin islands are seamounts.seamounts.

GuyoutGuyout

• A flat topped seamount which has A flat topped seamount which has subsided beneath the water’s surface subsided beneath the water’s surface because of wave action.because of wave action.

AtollAtoll

Volcanic Island ArcsVolcanic Island Arcs

• Curving Chains of volcanic islands Curving Chains of volcanic islands that occur over belts of deep-seated that occur over belts of deep-seated earthquakesearthquakes

• For example the Aleutian Islands are For example the Aleutian Islands are volcanic island arcs, formed over the volcanic island arcs, formed over the Aleutian oceanic trenchAleutian oceanic trench

BathymetricBathymetric

• Measurement of depths of the Measurement of depths of the oceans; also the data derived from oceans; also the data derived from such measurement, especially as such measurement, especially as compiled in a topographic map.compiled in a topographic map.

Exploring the Ocean FloorExploring the Ocean Floor

• Challenging at bestChallenging at best

• Single soundingsSingle soundings

• Sonar (single beam)Sonar (single beam)

• Multibeam sonarMultibeam sonar

• Sidescan SonarSidescan Sonar

• Satellite surface water topographySatellite surface water topography

Ocean Topography QuizOcean Topography Quiz

• 1. Most seamount islands are found in the 1. Most seamount islands are found in the ___________ Ocean Basin.___________ Ocean Basin.

• 2. T/F Volcanic Island arcs are associated 2. T/F Volcanic Island arcs are associated with subduction zones in zones of with subduction zones in zones of convergence?convergence?

• 3. In ocean basins, the youngest crust 3. In ocean basins, the youngest crust material would be found closest to or farthest material would be found closest to or farthest from the oceanic ridge?from the oceanic ridge?

Ocean Topography QuizOcean Topography Quiz

• 4. Submarine canyons are associated 4. Submarine canyons are associated with what part of the ocean’s topography?with what part of the ocean’s topography?

• 5. The continental shelf is an extension of 5. The continental shelf is an extension of the __________?the __________?

• 6. What is the longest mountain chain on 6. What is the longest mountain chain on earth?earth?

Ocean Topography QuizOcean Topography Quiz

• 7. For the North American Continent, the 7. For the North American Continent, the continental slope would be steeper on the continental slope would be steeper on the east or west coast?east or west coast?

• 8. The best surfing would be on the west or 8. The best surfing would be on the west or east coast of North America?east coast of North America?

• 9. The most accessible beaches in North 9. The most accessible beaches in North America would be on the west or east coast?America would be on the west or east coast?