Explore the Sea Floor

8 September 2014

Tallest Mountain on Earth

Mauna Kea Mount Everest

Seafloor is DynamicMariana Trench: deepest part of the ocean (11,000m)

Average ocean depth ≈ 3,700 meters (m)

Seafloor is DynamicSeafloor has hills, valleys, plains, river deltas, volcanoes, mountains and canyons.

Continental Shelf: gently sloping land area around the edges of continents.

Abyssal PlainFlat featureless plain making up a large part of the ocean floor.

Continental SlopeSteep Slope leading from the edge of a continent down to the seafloor.

Continental RiseHill of sediment at the bottom of the steep slope near the seafloor.

Submarine CanyonSteep-sided underwater alley near the edge of a continent.

Ocean Life?We know more about the surfaces of Luna and Mars than know about the Sea Floor. Why?

Measuring Ocean Depth: Plumb LineA plumb line had knots tied in it at regular intervals and weight (plumb) attached to the end.

Measuring Ocean Depth: SonarSonar mapping: using echoes to learn about the surrounding environment.

Knowing the speed of sound (1500 m/s)and time of echo return allows for depth measurement.

Distance = [(1/2)TV]

Question: If a sonar sends out a pulse of sound (ping) to the sea floor and it returns 8 seconds later, how deep is that section of the sea floor?

Answer???

Sonar Types: MultibeamSonar pulse emitted from hull. Data recorded over larger area than side scan sonar.

Sonar Types: MultibeamBest for depth information. Shallow = red. Deep = blue.

Sonar Types: Side ScanSonar pulse emitted from towfish (dragged behind ship or attached to submersible).

Sonar Types: Side Scan

image related to intensity of echo; harder objects send more intense echoes. Ideal for shipwrecks.

Satellite MappingSonar and plumbline mapping too expensive and time-consuming.

Satellite mapping more feasible and less expensive.

Satellite Mapping

Bathymetry: underwater topography.

Check on Learning1. What is the tallest mountain on Earth?2. What is the average ocean depth?3. A difference between multi beam and side scan?4. What is the continental shelf?5. What is bathymetry?6. What is a submarine canyon?7. What is average speed of sound underwater?8. What is the equation for determining depth?9. What does red indicate on an ocean map?10. What sonar is best for locating shipwrecks?