OCEANIC TOPOGRAPHY By Greg Schwab May 7, 2007

Competency 39 The teacher understands structure and function of the hydrosphere The teacher understands structure and function of the hydrosphere39.9 The beginning teacher identifies the characteristics of different ocean zones (e.g., coastal, lighted, deep, estuaries, bays). The beginning teacher identifies the characteristics of different ocean zones (e.g., coastal, lighted, deep, estuaries, bays).

TEKS: Geology, Meteorology, Oceanography (11) The student knows characteristics of oceans. The student is expected to: (11) The student knows characteristics of oceans. The student is expected to: (11A) Identify physical characteristics of ocean water including salinity, heat capacity, colligative properties, and density. (11A) Identify physical characteristics of ocean water including salinity, heat capacity, colligative properties, and density. (11C) Compare the topography of the ocean floor to the topography of the continents. (11C) Compare the topography of the ocean floor to the topography of the continents.

Word Wall Continental ShelfSeamount Continental SlopeGuyout Continental RiseAtoll Oceanic BasinVolcanic Island Arc Oceanic RidgesBathymetric Oceanic Trenches

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

Characteristics of the shelf Considered part of the continent not the ocean Considered part of the continent not the ocean Slopes gently away from land for an average of 75km (47 miles) Slopes gently away from land for an 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 than other parts Much wider on some parts of the continents than other parts Retains features of the adjacent land that is above water Retains features of the adjacent land that is above water

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

Characteristics of the slope Transition between the continent and the deep ocean basin Transition between the continent and the deep ocean basin Water depth ranges from 120 m (390 ft) to 3,000 m (10,000 ft) Water depth ranges from 120 m (390 ft) to 3,000 m (10,000 ft) Width of the slope is km (12-25 miles) Width of the slope is km (12-25 miles) Steeper than the shelf Steeper than the shelf Some slopes have submarine canyons Some slopes have submarine canyons

Submarine Canyons Long deep-sided trenches extending from the top of the slope to the ocean basin Long deep-sided trenches extending from the top of the slope to the ocean basin Can be similar in size and depth to the Grand Canyon Can be similar in size and depth to the Grand Canyon Believe to been formed by turbidity currents (a muddy current produced by underwater landslides) Believe to been formed by turbidity currents (a muddy current produced by underwater landslides)

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

Characteristics of rise Less steep than continental slope Less steep than continental slope Created mainly by sediment deposits from turbidity currents flowing down submarine canyons. Created mainly by sediment deposits from turbidity currents flowing down submarine canyons.

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

North American East Coast

North American Gulf Coast

North American East Coast

North American West Coast

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

Characteristics of the Basin Deepest part of the ocean floor Deepest part of the ocean floor Under 4-6 km (2-4 miles) of seawater Under 4-6 km (2-4 miles) of seawater Features include: Abyssal plain, Oceanic ridges, Oceanic trenches, and Seamounts Features include: Abyssal plain, Oceanic ridges, Oceanic trenches, and Seamounts Ocean basin and ridges cover more than half the earth’s surface Ocean basin and ridges cover more than half the earth’s surface More surface area than all of the land continents More surface area than all of the land continents

Abyssal Plain The practically level plain of the ocean basin. Covers an area equal to the continental land mass Covers an area equal to the continental land mass

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

Characteristics of ridges Part of a chain of mountains that are 84,000 km long Part of a chain of mountains that are 84,000 km long Mid-Atlantic Ridge is longest mountain chain on earth Mid-Atlantic Ridge is longest mountain chain on earth Ridges are spreading centers or divergent plate boundaries where new ocean floor is created Ridges are spreading centers or divergent plate boundaries where new ocean floor is created

Oceanic Trenches Long, narrow, deep troughs with steep sides that run parallel to the edge of continents

Characteristics of trenches Extend 8-11 km below sea level Extend 8-11 km below sea level Long narrow basins Long narrow basins Develop adjacent to subduction zones Develop adjacent to subduction zones Zone of convergence Zone of convergence Form parallel to continents Form parallel to continents

Seamounts Steep submerged volcanic peaks on the abyssal plain.

Characteristics of seamounts More than 10,000 scatter the ocean basin More than 10,000 scatter the ocean basin By definition rise more than 1 km (0.6 miles) above the ocean floor. By definition rise more than 1 km (0.6 miles) above the ocean floor. Can extend above sea level (called an island) Can extend above sea level (called an island) Most Pacific Basin islands are seamounts. Most Pacific Basin islands are seamounts.

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

Atoll

Volcanic Island Arcs Curving Chains of volcanic islands that occur over belts of deep-seated earthquakes Curving Chains of volcanic islands that occur over belts of deep-seated earthquakes For example the Aleutian Islands are volcanic island arcs, formed over the Aleutian oceanic trench For example the Aleutian Islands are volcanic island arcs, formed over the Aleutian oceanic trench

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

Exploring the Ocean Floor Challenging at best Challenging at best Single soundings Single soundings Sonar (single beam) Sonar (single beam) Multibeam sonar Multibeam sonar Sidescan Sonar Sidescan Sonar Satellite surface water topography Satellite surface water topography

Ocean Topography Quiz 1. Most seamount islands are found in the ___________ Ocean Basin. 1. Most seamount islands are found in the ___________ Ocean Basin. 2. T/F Volcanic Island arcs are associated with subduction zones in zones of convergence? 2. T/F Volcanic Island arcs are associated with subduction zones in zones of convergence? 3. In ocean basins, the youngest crust material would be found closest to or farthest from the oceanic ridge? 3. In ocean basins, the youngest crust material would be found closest to or farthest from the oceanic ridge?

Ocean Topography Quiz 4. Submarine canyons are associated with what part of the ocean’s topography? 4. Submarine canyons are associated with what part of the ocean’s topography? 5. The continental shelf is an extension of the __________? 5. The continental shelf is an extension of the __________? 6. What is the longest mountain chain on earth? 6. What is the longest mountain chain on earth?

Ocean Topography Quiz 7. For the North American Continent, the continental slope would be steeper on the east or west coast? 7. For the North American Continent, the continental slope would be steeper on the east or west coast? 8. The best surfing would be on the west or east coast of North America? 8. The best surfing would be on the west or east coast of North America? 9. The most accessible beaches in North America would be on the west or east coast? 9. The most accessible beaches in North America would be on the west or east coast?