Oceanography
Ch. 17 & 19
1. Oceanography is the study of the world’s oceans.
2. The World Oceans
70% of the Earth’s Surface is covered by Oceans.
There are 4 major oceans.
Pacific, Atlantic, Indian and Arctic
*Possible 5th ocean-Southern Ocean
The average depth of the oceans is 4 times deeper than the average height of the
continents
3. Salinity is a measure of the dissolved solids in the Ocean.
On average sea water is 35 parts dissolved salt per 1000 grams of sea water.
Written as 35000
Heavy rains, rivers, glaciers cause oceans to fall below the salinity average.
Baltic Sea 30000
Evaporation and freezing cause oceans to rise above the salinity average.
Mediterranean Sea 40000
4. Electrical Conductivity is used to measure the salinity of sea water.
Currents move more easily thru water with greater quantity of dissolved salts.
Salinity helps to identify water masses
5. Composition of Sea Water
Salt is present in sea water in the form of dissolved ions.
Sodium ions Na+
30.6%
Chloride ions Cl-
55.04%
Sulfate ions SO4
7.7%
Magnesium Mg2+
3.7%
Calcium Ca
1.2%
Potassium K
1.1%
The percent of dissolved ions in sea water is the same for all sea water no matter the salinity or location.
#6. There are 3 Temperature Zones.
Mixed Temp. Zone
Sunlight hits this zone
Depth depends on the angle of the sunlight.
300m deep at equator, 100m deep at poles.
Wave and currents mix water and change temp.
Thermocline Zone
Temperature drops quickly.
Ave depth 300m-1000m.
Deep Water Zone
Temp between 20C - 50C.
No light for plankton
CO2 accumulates in this Zone and is the most abundant gas.
#7. Sunlight and Marine Life.
Phytoplankton is the most important group of plants in the mixed zone.
These plants are floaters and drifters.
Most abundant phytoplankton is the Diatom.
One celled organism that builds shells made of silica.
Phytoplankton use photosynthesis to produce oxygen
More important than the rain forest.
Zooplankton are microscopic floating animals.
Eat the Phytoplankton.
Larger Fish and Whales eat the Zooplankton
8. Continental Margins
Continental Shelves
Are a part of the continent that is underwater
They are extremely flat
They extend from the shoreline of the continent to the Continental Slope.
Active Continental Margin
Very Narrow Shelf
Bordered by a trench
Shoreline is rugged with coastal Mountains
Ex: Pacific Coast of South America
Passive Continental Margin
Broad Shelf
No bordering trench
No Rugged Coastal Mountains
Ex: Atlantic Coast of North America
Continental Slope
Begins at the shelf edge.
Where water depth starts to increase rapidly.
Depth from 200m to 3 Km.
Beyond slope is the Ocean Floor.
Change from Continental Crust to Ocean Crust.
Slope can be cut by Submarine Canyons.
Can be as large as the Grand Canyon
9. Ocean Basins
Abyssal Plains
Extremely Flat
Composed of Sediments
Up to 1 Km thick
Sediments came from continents
Abyssal Hills
Small rolling hills near continental margins.
1-10 km across
A few 100 meters high
Seamounts, Guyots and Coral Atolls
Seamount- cone shaped mountain peaks.
Guyots - Flat top seamounts.
Originally above sea level.
Tops remove by wave action.
Coral Atolls.
Ring shaped Coral Islands.
Formed from sinking ocean floor
Coral reef “grows” at the top
Mid-Ocean ridges
Shallow areas where mountain chains are being volcanically built.
The ocean bottom is youngest at the mid ocean ridge.
10. Surface Currents
Ocean Currents are any continuous flow of water along a broad path in the Ocean.
Currents and Winds
The diving force of the surface currents is wind.
Trade winds affect the path of each current circle that occurs near the equator.
Push North and South Equatorial Currents
Westerly winds drive the polar portion of the current circles.
Drive the currents in the Polar region.
Warm Ocean Currents
Flow away from the Equator.
Gulf Stream
Brings warm water from the Caribbean Sea.
Flow up the East coast of N. America.
Flows across the Atlantic ocean
Brings warmer climates than expected.
Cold Currents
Flow towards the Equator
Causes Icebergs and thick fog in the Atlantic Ocean.