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

depthpart 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 shelf Seamount

Volcanic islandContinental slope

Continental shelf

Continental

slope

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:

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

• ….continental slope

Questions

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.