The Ocean Floor --subsurface topography-- Ch 13, section 2 (before the 1900’s scientists thought the ocean floor was completely flat)

Sonar (sound navigation and ranging) --invented during WWI-- to find depth: use the formula: depth= V x t (remember that you only want half the time)—units=meters …where velocity of sound in ocean water is about 1,500 m/s

Water pressure Water Pressure demo (with 2L bottle) Water pressure increases with depth  part of Titanic

Continental Margin

>>submarine canyons caused by erosion and underwater landslides

ABYSSAL PLAIN Flat area of ocean floor

Mid-Ocean Ridge Divergent boundary Sea-floor spreading New sea floor formed

What do you notice about the shape of the mid-Atlantic ridge?

Seamount Underwater volcanoes If they reach the surface they form islands, like Iceland. FYI—called guyots if flat-topped (due to erosion)

Iceland

TRENCH At convergent boundary Ex: the Mariana Trench is the deepest known place on earth ---11034 meters (36200 ft) deep

Features of the Ocean Floor (website—needs sound)

The Ocean Floor Continental slope Continental slope Volcanic island Continental shelf Continental shelf Seamount Abyssal plain Mid-ocean ridge Trench

3D model of ocean floor (as a group) After you build the ocean floor, use toothpicks and sticky labels to identify the following ocean features: 1. continental shelf 2. continental slope 3. MID-ocean ridge 4. abyssal plain 5. seamount 6. trench—should not be right next to mid-ocean ridge (should be at subduction zone)

Omit section 3, except:

Questions If you were able to walk along the ocean bottom from a beach, which feature would you reach after the continental shelf? ….continental slope

The area under water that is closest to the shoreline is the A. continental shelf B. continental slope C. mid-ocean ridge D. benthic

The __________ is the broad, FLAT part of the deep-ocean basin A. abyssal plain B. continental shelf C. mid-ocean ridge D. benthic

At which point in the diagram above would hot magma most likely rise through the ocean floor to eventually form a volcanic island? Point B

Which is most like a mountain RANGE? A. A seamount B. A guyot C. The abyssal plain D. The mid-ocean ridge Note: A seamount is a single underwater mountain.