You need to picture our oceans as giant sinks. Water falls on land and often finds its way into either lakes or rivers. The water residency time in these is comparatively short, with rivers, fed by lakes, flowing out to the sea. Water also travels under the ground.
Salt can be found in its pure form or within other compounds but is readily dissolved when water flows through it. Water, laden with large amounts of various minerals, will eventually reach the ocean where the water cycle restarts. Water is evaporated from the ocean surface but the salt is too heavy to be evaporated and remains in the sea. Hence, since the oceans formed on the Earth, they have been recieving salt from land and have thus become increasingly more saline.
One more interesting fact is that like many things on earth, the level of salt in the ocean has reached an equilibrium at 35 parts per million. It is thought that there are many factors responsible for this including biological and tectonic (formation of new minerals etc).
Salt can be found in its pure form or within other compounds but is readily dissolved when water flows through it. Water, laden with large amounts of various minerals, will eventually reach the ocean where the water cycle restarts. Water is evaporated from the ocean surface but the salt is too heavy to be evaporated and remains in the sea. Hence, since the oceans formed on the Earth, they have been recieving salt from land and have thus become increasingly more saline.
One more interesting fact is that like many things on earth, the level of salt in the ocean has reached an equilibrium at 35 parts per million. It is thought that there are many factors responsible for this including biological and tectonic (formation of new minerals etc).
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