where did fresh water come from.

[ihasanzongi]

I was thinking last night when i was watching my fish before i went to sleep. Where did fresh water come from? We all know that there was just one large landmass like 250 million years ago, but wouldnt that be just all salt water because that would be our oceans all around it right. then I was thinking what about ice? But that would have to come from the only large water we had at the time in the north and south poles, saltwater. My only lead I could think of was rain fall? but would have been enough over the millions of years to give us the amount of freshwater our world has? SO i ask you, where did fresh water come from?

 

[Noto]

Rain. When water evaporates from the sea, the salt is left behind. There is enough to keep our rivers constantly flowing (well, most of 'em).

 

[CDickes1988]

Rain. When water evaporates from the sea, the salt is left behind. There is enough to keep our rivers constantly flowing (well, most of 'em).

^ What he said!

 

[ihasanzongi]

ohh, thanks I didnt think about how much rain would add up over 200 million years.

 

[Noto]

It didn't take 200 million years; our world has had plenty of fresh water for most of its existence. All the freshwater on earth cycles through in a matter of a few centuries; most of it in just a few years. What I mean is, if you could track the history of any given water molecule, no one of them would exist as part of a body of fresh water for more than a few hundred years. It would either evaporate, return to the sea, or be taken up by some chemical or organic process.

 

[arherp]

Water doesn't reproduce, it doesn't add up.

 

[Moontanman]

Most scientists think even the oceans were fresh to begin with, minerals brought down from the land dissolved by rain and minerals dissolved via the interaction of the sea and the spreading of lava at mid ocean ridges slowly concentrated our oceans over eons. Evaporation condenses to form rain and rain transports more dissolved minerals and salts to the ocean sea bed subduction takes some of the salts out of the water only to be taken back to the sea as volcano's erupt on land and are slowly eroded by rain again. It's continuous cycle and there is no need for the rain to "reproduce or add up"

 

[Thedaniokeeper]

I just saw a Bill Nye on it today in class...

 

[pcfriedrich]

ohh, thanks I didnt think about how much rain would add up over 200 million years.

actually, in the beginning (a few billion years ago) the ocean was all fresh water. over the eons the ocean is slowly getting saltier and saltier from the accumulation of dissolved minerals picked up from rocks and soil by rivers that drain into the ocean. in another couple billion years, the sea will be too salty to support most contemporary marine life.

 

[Bud8Fan]

in another couple billion years, the sea will be too salty to support most contemporary marine life.

Life adapts.