1. Oceanography
Unit 2

2. Earth’s Layers Four distinct layers Inner Core (1,228 km radius)
Hottest
High density solid nickel and iron
Outer Core (2,260 km thick)
Hot
Molten nickel and iron
Mantle (2,890 km thick)
Less dense than inner and outer cores
Molten silicates
Crust (8-12 km thick)
solid

3. Crust
Mantle
Outer Core
Inner Core
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4. Earth’s crust “floats”
Lithosphere – strong, rigid behavior
Consists of crust and the upper mantle material fused together
Asthenosphere – weak, ductile behavior
Low velocity plastic layer (molten magma)

5. Earth’s Crust Oceanic Crust (Basalt) Continental Crust (Granitic)
Lots of silica and iron
More dense than continental crust
Always subducts under continental
Not much more than 7 km thick generally
Continental Crust (Granitic)
Lots of silica and aluminum
A few km (edge of continents) to over 32 km (middle of continents)

8. 12 Major Plates

9. Mountain Mover, Earth Shaker

10. Oceanic Ridges/Rises Divergent oceanic plate boundary
Undersea mountain ranges
Rift Valley – where volcanism occurs and new crust is created
Mid-Atlantic Ridge – 2.2 inches/year
East Pacific Rise – 12.6 inches/year
video

11. Deep Sea Trenches Subduction Zones – Plate Convergence
May be twice as deep (almost 12,000 m) as the regular deep-sea floor (up to 6,000 m)
Excess crust subducted and melted
Earthquake activity

12. Hydrothermal Vents
Seafloor outlet for high-temperature water and associated mineral deposits (a hot spring)
High interest area of study
video

13. Brine Shrimp Life Cycle

14. Ocean Soundings
Our ability to accurately map the features of the sea floor has been acquired only recently and continues to improve with advancing technology.
Early soundings included:
Rocks tied to ropes
Cannonballs and piano wire
Now:
Echo soundings
consistent speed of sound in seawater and accurate time measurements

15. Continental Margin
Consists of shelf, shelf break, slope, and rise

16. Passive vs. Active Passive continental margins:
found around the rim of the Atlantic Ocean
are not plate boundaries
have little or no seismic or volcanic activity
form when a continent rifts apart creating a new ocean basin between the fragments.
Active continental margins:
are found around the rim of the Pacific Ocean
are plate boundaries
are typically seismically and/or volcanically active
tend to be relatively narrow

17. Continental Margin Continental Shelf
very flat edges of the continental crust covered by marine waters
Narrow shelves associated with steep slopes
Wider shelves associated with relatively flat continental regions

20. Seafloor Features Submarine Canyons Deep v-shape
Cut across continental margins
Some can be traced from river systems
Abyssal Plain
Flat ocean basin floor
Extends seaward from continental slope and rise

21. Seafloor Features Abyssal hills Less than 1000 m high Seamounts
Greater than 1000 m high
Guyots
Flat-topped seamounts
Islands
Seamounts that rise above the sea surface

23. Coral Reefs Often built on islands and seamounts Fringing Reef
Attached directly to the shore of an island or continent
Barrier Reef
Parallels land but is some distance offshore with water between
Atoll
Ring-shaped coral reef that encloses a lagoon