1. Ocean Features

2. Bathymetry
Bathymetry-(Bathos=depth;metry-measurement) Measurement of ocean depths and charting the shape of the ocean floor
Sounding- Using a line with heavy weight to probe ocean’s depths
Fathom- unit of measurement specifically for ocean depth measurement (1 fathom=1.8 meters=6 feet)

3. HMS Challenger
1872- made first systematic measurements using sounding technology
Noticed that depth varied indicating that the ocean floor was not flat, but had relief just as land does

4. Advancing Technology SONAR Technology- Sound, Navigation, And Range
1900s- Echo Sounders
Sends a sound signal to determine depth and shape of ocean floor. Early technology not very accurate
1950s- Precision Depth Recorder (PDR)
Used high-frequency sound beam to measure depths within 1 meter accuracy
Current technology- Multibeam Echo Sounders
Use multiple frequencies of sound simultaneously giving more precise data

5. Ocean Floor Provinces Continental Margins Deep Ocean Basins
Shallow water areas close to continents
Deep Ocean Basins
Deep water areas farther from land
Mid-Ocean Ridge
Shallower areas near the middle of the ocean

6. Continental Margins Passive Margins Active Margins
Imbedded within the interior of lithospheric plates and are not in close proximity to plate margins
Lack tectonic activity
Active Margins
Associated with lithospheric plate boundaries and are marked by a high degree of tectonic activity

7. Active Margins Convergent Active margins Transform Active margins
oceanic-continental convergent plate boundaries
Features
Continental arc, narrow shelf, steep slope, offshore trench
Transform Active margins
Transform plate boundaries
Faults create linear islands, banks, deep basins

9. Features of Continental Margins
Continental shelf- flat zone extending from the shore beneath the ocean to a point where slope angle increases dramatically
Average width- 70 KM
Ranges from a meters to 1500 KM
Shelf Break- Point where increase in slope angle occurs
Can contain coastal islands, reefs, and raised banks

10. Features of Continental Margins
Continental borderland- occurs in faulted areas (California). High degree of relief on shelf
Continental slope- this is where deep ocean basins begin
Continental rise- transition zone between the continental margin and the deep ocean floor
Graded bedding, produced by turbidity currents. Layered sedimentation with heavier sediments settling out first. Decrease in sediment size from bottom to top

12. Underwater Canyons
Submarine canyons- V-shaped and have branches or tributaries with steep overhanging walls
Thought to occur because of turbidity currents
Turbidity currents- Underwater avalanches of muddy water mixed with rocks and other debris
Mass moves from earthquakes, hurricanes, or other disturbance carving the canyon

13. Deep Ocean
Abyssal Plains- Extend from the base of the continental rise into the deep-ocean basins.
Flat, depositional surfaces with very slight slopes
Average between 4500 meters and 6000 meters deep
Suspension Settling- fine particles of sediment slowly drift onto the deep ocean floor
This is how abyssal plains form

15. Underwater Volcanoes
Seamounts: Below sea level, but rise 1 kilometer above the deep ocean floor
Seaknolls (abyssal hills) less than 1 kilometer above the deep ocean floor

16. Ocean Trenches
Deep linear scars in the ocean floor. They are very narrow and steep
Occurs along active continental margins, where there is a convergent plate boundary
The side nearest to land can be volcanic arcs (islands of Japan), or continental arcs (Andes Mountains)

17. Mid-Ocean Ridge
Earth’s longest mountain chain – 75,000 kilometers/46,600 miles
Divergent boundary
Entirely volcanic- composed of basaltic lavas
Rift valley occurs along its crest
Underwater lava flows- Pillow lavas

19. Hydrothermal Vents Hot springs which occur in the central rift valley
Appearance depends on temperature of water
Warm-water vents are below 30oC (86oF) and are clear in color
White smokers are between 30oC and 350oC (86oF- 662oF) and are white in color
Black smokers are above 350oC (662oF) and are black in color

21. Mid-Ocean Ridge cont.
Oceanic ridges have a rift valley and steep rugged slopes
Oceanic rises have slopes that are gentler and less rugged

22. Mid-Ocean Ridge
Transform Faults cut the mid-ocean ridge in a number of places
These faults are perpendicular to the mid-ocean ridge and give the ridge a zigzag appearance
Many earthquakes occur here
Fracture Zones also extend from the mid-ocean ridge, but are much different from transform faults