4.1.6 Oceanography notes

1. 4.1.6.1Ocean floor relief: continental shelf, slope, abyssal plains, ridges and trenches

   The ocean floor is not flat: moving out from the coast it steps down from the shallow continental shelf, over the steeper continental slope, to the wide deep sea plains, broken by long mid-oceanic ridges, volcanic seamounts and deep narrow trenches.

   Advanced · 8 min · Full course
2. 4.1.6.2Relief of the Pacific, Atlantic and Indian Oceans: major ridges, trenches and deeps

   The Pacific is the largest and deepest ocean with a rim of trenches, the Atlantic is an S-shaped ocean split down the middle by the Mid-Atlantic Ridge, and the Indian Ocean has an inverted-Y ridge system and few deeps.

   Advanced · 8 min · Full course
3. 4.1.6.3Temperature of ocean water: distribution and the thermocline

   Ocean water is warmest at the surface in low latitudes and cools towards the poles and with depth; the sharp drop in temperature below the warm surface layer is the thermocline.

   Advanced · 7 min · Full course
4. 4.1.6.4Salinity of oceans and seas: controlling factors and distribution

   Salinity is the amount of dissolved salt in sea water; it averages about 35 parts per thousand and rises where evaporation is high and falls where rain, rivers or melting ice add fresh water.

   Advanced · 7 min · Full course
5. 4.1.6.5Ocean currents: causes and warm and cold currents

   Ocean currents are steady flows of water in a set direction, started by solar heating, wind, gravity and the Coriolis force and shaped by differences in water density; warm currents flow from the tropics poleward, cold currents from the poles towards the equator.

   Advanced · 8 min · Full course
6. 4.1.6.6Major currents of the Atlantic, Pacific and Indian Oceans and their effects

   Each ocean has a loop of warm currents along the eastern shores of continents and cold currents along the western shores; they decide whether a coast is mild or cold, wet or desert, and where the great fishing grounds lie.

   Advanced · 8 min · Full course
7. 4.1.6.7Waves and tides: spring and neap tides, tidal bores and tidal energy

   Waves are wind energy moving across the sea surface while the water itself only circles in place; tides are the regular twice-daily (or daily) rise and fall of the sea caused mainly by the Moon's pull, strongest at spring tides and weakest at neap tides.

   Advanced · 9 min · Full course
8. 4.1.6.8Coral reefs: conditions, fringing, barrier and atoll types and coral bleaching

   Coral reefs are limestone structures built by colonies of tiny polyps living with algae in warm, clear, shallow tropical seas; they grow as fringing reefs, barrier reefs or atolls and are bleaching more often as the oceans warm.

   Advanced · 8 min · Full course
9. 4.1.6.9Ocean resources and the Law of the Sea: UNCLOS, territorial waters and EEZ

   The oceans hold food, energy and minerals, and the 1982 UN Convention on the Law of the Sea (UNCLOS) divides them into zones — 12 nautical miles of territorial sea, a 24-mile contiguous zone, a 200-mile exclusive economic zone and the high seas — that decide who may use what.

   Advanced · 10 min · Full course

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