Currents

[Lestat]

What gives an ocean current its direction? I don't think it's the wind. Is it the earth's rotation? Differences in sea levels? Sorry for the dumb question, I'm just curious.

Also, has anyone heard of something called the water cycle? I don't really remember it, but it has something to do with how long it takes a current volume of water to circumnavigate the globe. And while I'm at it...

Do water molecules at the very deepest depths of the ocean ever make it to the surface and visa~versa? Thanks.

[Copernicus]

Currents are analagous to wind. Temperature gradiants at different depths are the basic cause. Then , just as wind is affected by what it encounters, current is affected by the characteristics of the ocean floor, bodies of land it encounters, etc.

not sure about the "water cycle"

Third question...why wouldnt they? molecules in liquid would be subject to the equivalent of Brownian Motion in gases, and eventually some should reach the surface randomly. Also see the currents question..temperature gradiants still exist at the ocean floor which will cause undersea currents, as the very cold water meets somewhat warmer water an local equilbrium would be reached, warming the colder water, causing it to rise, and so on.

[CheckRaise]

Lesat -

The water cycle is the circulation of water throughout earth and it atmosphere.

http://img221.imageshack.us/img221/4341/usgswatercycle2zb.jpg

[AvivaSimplex]

The second google result for "ocean currents" answers most of your questions. http://earth.usc.edu/~stott/Catalina/Oceans.html