why is sea water salty?

Answer 1

Everyone who has been to the beach knows that seawater is salty. Everyone also knows that fresh water in rain, rivers, and even ice is not salty. Why are some of Earth’s waters salty and others not? There are two clues that give us the answer. First, “fresh” water is not entirely free of dissolved salt. Even rainwater has traces of substances dissolved in it that were picked up during passage through the atmosphere. Much of this material that “washes out” of the atmosphere today is pollution, but there are also natural substances present.

As rainwater passes through soil and percolates through rocks, it dissolves some of the minerals, a process called weathering. This is the water we drink, and of course, we cannot taste the salt because its concentration is too low. Eventually, this water with its small load of dissolved minerals or salts reaches a stream and flows into lakes and the ocean. The annual addition of dissolved salts by rivers is only a tiny fraction of the total salt in the ocean. The dissolved salts carried by all the world’s rivers would equal the salt in the ocean in about 200 to 300 million years.

A second clue to how the sea became salty is the presence of salt lakes such as the Great Salt Lake and the Dead Sea. Both are about 10 times saltier than seawater. Why are these lakes salty while most of the world’s lakes are not? Lakes are temporary storage areas for water. Rivers and streams bring water to the lakes, and other rivers carry water out of lakes. Thus, lakes are really only wide depressions in a river channel that have filled with water. Water flows in one end and out the other.

The Great Salt Lake, Dead Sea, and other salt lakes have no outlets. All the water that flows into these lakes escapes only by evaporation. When water evaporates, the dissolved salts are left behind. So a few lakes are salty because rivers carried salts to the lakes, the water in the lakes evaporated and the salts were left behind. After years and years of river inflow and evaporation, the salt content of the lake water built up to the present levels. The same process made the seas salty. Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean. Because of the huge volume of the oceans, hundreds of millions of years of river input were required for the salt content to build to its present level.

Rivers are not the only source of dissolved salts. About twenty years ago, features on the crest of oceanic ridges were discovered that modified our view on how the sea became salty. These features, known as hydrothermal vents, represent places on the ocean floor where sea water that has seeped into the rocks of the oceanic crust, has become hotter, and has dissolved some of the minerals from the crust, now flows back into the ocean. With the hot water comes a large complement of dissolved minerals. Estimates of the amount of hydrothermal fluids now flowing from these vents indicate that the entire volume of the oceans could seep through the oceanic crust in about 10 million years. Thus, this process has a very important effect on salinity. The reactions between seawater and oceanic basalt, the rock of ocean crust, are not one-way, however; some of the dissolved salts react with the rock and are removed from the water.

A final process that provides salts to the oceans is submarine volcanism, the eruption of volcanoes under water. This is similar to the previous process in that seawater is reacting with hot rock and dissolving some of the mineral constituents.

Will the oceans continue to become saltier? Not likely. In fact the sea has had about the same salt content for many hundred of millions if not billions of years. The salt content has reached a steady state. Dissolved salts are being removed from seawater to form new minerals at the bottom of the ocean as fast as rivers and hydrothermal processes are providing new salts.

Answer 2

Although I agree with the serious answers already given, a large amount of ions responsible for the "salty taste" of sea water may be due to the imput from mid-oceanic ridges. There are vents called black smokers and other vents called white smokers that spew much material into the oceans, raising its salinity.

Answer 3

"As water flows in rivers, it picks up small amounts of mineral salts from the rocks and soil of the river beds. This very-slightly salty water flows into the oceans and seas. The water in the oceans only leaves by evaporating (and the freezing of polar ice), but the salt remains dissolved in the ocean - it does not evaporate. So the remaining water gets saltier and saltier as time passes."

Answer 4

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of ~3.5%. This means that for every 1 litre (1000 mL) of seawater there are 35 grams of salts (mostly, but not entirely, sodium chloride) dissolved in it. This can be expressed as 0.6M NaCl or 0.6 mol·L-1 (if the salinity were due entirely to NaCl, which it is not).

Although a vast majority of seawater is found in oceans with salinity around the 3.5 %, seawater is not uniformly saline throughout the world. The planet's freshest (least saline) sea water is in the eastern parts of Gulf of Finland and in the northern end of Gulf of Bothnia, both part of the Baltic Sea. The most saline open sea is the Red Sea, where high temperatures and confined circulation result in high rates of surface evaporation and there is little fresh inflow from rivers. The salinity in isolated seas and salt-water lakes (for example, the Dead Sea) can be considerably greater.

Salinity and the main salt ions
The salinity of sea water (usually 3.5%) is made up by all the dissolved salts shown in the above table. Interestingly, their proportions are always the same, which can be understood if salinity differences are caused by either evaporating fresh water or adding fresh water from rivers. Freezing and thawing also matter.

Salinity affects marine organisms because the process of osmosis transports water towards a higher concentration through cell walls. A fish with a cellular salinity of 1.8% will swell in fresh water and dehydrate in salt water. So, saltwater fish drink water copiously while excreting excess salts through their gills. Freshwater fish do the opposite by not drinking but excreting copious amounts of urine while losing little of their body salts.

Marine plants (seaweeds) and many lower organisms have no mechanism to control osmosis, which makes them very sensitive to the salinity of the water in which they live.

The main nutrients for plant growth are nitrogen (N as in nitrate NO3-, nitrite NO2-, ammonia NH4+), phosporus (P as phosphate PO43-) and potassium (K) followed by Sulfur (S), Magnesium (Mg) and Calcium (Ca). Iron (Fe) is an essential component of enzymes and is copiously available in soil, but not in sea water (0.0034ppm). This makes iron an essential nutrient for plankton growth. Plankton organisms (like diatoms) that make shells of silicon compounds furthermore need dissolved silicon salts (SiO2) which at 3ppm can be rather limiting.

Answer 5

rain water travels to ocean through many obstructs such as the rocks, soil etc..., dissolves the minerals in them and carry along with to the sea which generally make the salty sense of the sea water

Answer 6

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.

Answer 7

becasue of all rivers of the world are meet with sea. so water of sea is Salty. It's my Opinion.

Answer 8

sea water contains most of the salts, so it is salty

Answer 9

the sality and pH level of the sea is more higher than the fresh water,
i think the pH level of the seal is 71% that will make the sea water salty.

Answer 10

That is because the micro-organisms living in the sea have the salty property.