Earth and Space Science / Unit 6: Water on Earth and the Oceans
6.4 Ocean Water and the Seafloor
Notes
- Ocean salinity averages about 35 parts per thousand (3.5%). Main salt: sodium chloride.
- Salinity is higher where evaporation is high and lower near river mouths and melting ice.
- Temperature drops quickly with depth through the thermocline.
- Seafloor features: continental shelf, slope, deep abyssal plain, trenches (deepest, such as the Mariana Trench), mid-ocean ridges and seamounts.
- Seawater is denser when it is colder and saltier.
Practice
Average ocean salinity is about:
35 parts per thousand equals 3.5%.
Which would make the surface water saltier?
Evaporation leaves salt behind.
The deepest parts of the ocean are:
Trenches form at subduction zones.
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