[thedoc (OP)]

Joyce Heard  asked the Naked Scientists:
   
Chris et al,

What makes ocean water salty? What is the range of saltiness of the various world oceans?

I enjoy your show wherever I am via podcast. I try not to miss a show but if possible would love a heads up if you are able to use my question. I'm constantly impressed by how many hats you and your presenters manage to juggle, including research, parenting travel etc.

Best regards,

Joyce Heard
Sidi Ifni, Morocco

What do you think?

[Sprool]

Salt in the ocean comes from the land. The elements that make up salts, such as chlorine and sodium, started out in rocks. Water and acids eroded the rocks, and rivers carried the elements into the sea. The oceans usually contain 35 parts of salts for every 1000 parts of sea water. This is lower in some places where there is a lot of fresh water coming into the ocean. It is higher where the Sun is very strong and evaporates more of the water. When all the water is gone, the salts are left behind as solid, white crystals.
THe water cycle takes evapotated water from the sea (leaving the salt behind) and depositing it as rain over the land masses, thus rainwater is not salty, so rivers are initially not salty but will continue to carry with them traces of salts from the land the flow over, back into the sea again.
 

[Ophiolite]

Based upon the average salt content of fresh water and the salinity of the ocean, researchers attempted to estimate the age of the Earth. They invariably came out with a comparatively young age - the order of a couple of hundred million years. Only once plate tectonics was accepted ws it realised that salt was recycled through the ocean via deposition in evaporites and entrapment in subducting oceanic plates.