why is the sea water salty?

Salt is the compound sodium chloride (NaCl). In the ocean however, the two elements are not combined but are separated from each other by the water molecules. The sodium is dissolved in the water as a positively charged atom, the chlorine as a negatively charged atom (these are called ions). Take away the water in between them and they attract and "stick" together as salt. But these ions did not get into the ocean as salt however. The chlorine comes from volcanos (most active volcanos are underwater) and the sodium from the weathering and erosion of minerals that contain sodium. The first oceans (3 billion years before the dinosaurs) were not salty, but as weathering and volcanos added sodium and chlorine, and evaporation cycled out the water, the salintiy increased. This saltiness has been the same for a long time however, because there are several natural processes that remove salt at about the same rate new salt is added. I'm afraid I don't know right now the effects of salinity on promoting the use of the land by organisms, but I intend to look into it. I doubt salinity affects global warming, but the global increase in air and ocean temperatures may change evaporation and precipitation, and that can change salinity. One dangerous effect of global warming melting the Greenland glaciers faster than at any time in past half billion years or so (even faster than at the end of the ice ages) could be a drop in the salinity in the North Atlantic that prevents that water from sinking. This could divert the Gulf Stream farther away from England and northern Europe resulting in a rapid cooling of their climate. The economic consequences could mess up the whole worlds economy. i think u can understand. happy mylot day.

because of the salts dissolved in it.

All water, even rain water, contains dissolved chemicals which scientists call "salts." But not all water tastes salty. Water is fresh or salty according to individual judgment, and in making this decision man is more convinced by his sense of taste than by a laboratory test. It is one's taste buds that accept one water and reject another. A simple experiment illustrates this. Fill three glasses with water from the kitchen faucet. Drink from one and it tastes fresh even though some dissolved salts are naturally present. Add a pinch of table salt to the second, and the water may taste fresh or slightly salty depending on a personal taste threshold and on the amount of salt held in a "pinch." But add a teaspoon of salt to the third and your taste buds vehemently protest that this water is too salty to drink; this glass of water has about the same salt content as a glass of sea water. Obviously, the ocean, in contrast to the water we use daily, contains unacceptable amounts of dissolved chemicals; it is too salty for human consumption. How salty the ocean is, however, defies ordinary comprehension. Some scientists estimate that the oceans contain as much as 50 quadrillion tons (50 million billion tons) of dissolved solids. If the salt in the sea could be removed and spread evenly over the Earth's land surface it would form a layer more than 500 feet thick, about the height of a 40-story office building. The saltiness of the ocean is more understandable when compared with the salt content of a fresh-water lake. For example, when 1 cubic foot of sea water evaporates it yields about 2.2 pounds of salt, but 1 cubic foot of fresh water from Lake Michigan contains only one one-hundredth (0.01) of a pound of salt, or about one sixth of an ounce. Thus, sea water is 220 times saltier than the fresh lake water. What arouses the scientist's curiosity is not so much why the ocean is salty, but why it isn't fresh like the rivers and streams that empty into it. Further, what is the origin of the sea and of its "salts"? And how does one explain ocean water's remarkably uniform chemical composition? To these and related questions, scientists seek answers with full awareness that little about the oceans is understood.

Maybe in the 19th century people got bored of their chips and chucked them in the sea. But seriously......salt has just be dragged donw to the sea bed with erosion and its the lowest place it can go so it just stays there.