why is sea water salty?

Answer 1

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.

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

First you need to look at the water cycle, (1) pure water evaporates from the sea and becomes a cloud, (2) the cloud rains over land (3) the water drains to rivers and streams, as they do this (4) and because water is a natural solvent, (5) the water collects minerals and natural salt from the land (6) and these is deposited in the sea via streams, and rivers (7) because this process was repeated every day for billions of years, there are a great concentration of dissolved natural salt in the sea. Lastly look at a good science book. I hope that the above rough idea helps you why and how the sea become salty.

Answer 3

As the rains fall and water flows over the land, the water dissolves salt out of the rocks, washes the salt into streams, then rivers, and finally carries the salt to the sea. The salt stays in the sea because no water flows out of the sea - just as no water flows out of the Great Salt Lake in Utah. When seawater evaporates to form clouds, almost all of the salt stays behind. The left-behind salt slowly accumulates until, over the eons, the seas became salty-now about three percent.

That's the simple picture, which is true but incomplete.

Seawater also picks up salt from the oceanic crust. The ocean floor has places, called hydrothermal vents, where seawater seeps into the rocks of the oceanic crust, gets hot, dissolves salts from the crust, flows back into the ocean with its salt load, and increases the ocean's saltiness.

Volcanoes erupting under the sea is yet another way the sea gets salty. Seawater, once again, dissolves salts from the molten rock.

Will the seas keep on getting salty? No. The oceans have stayed at about three percent for hundreds of million years because they lose salt in several ways.

Pick up a clamshell and heft it in your hand: heavy. All creatures need sodium to live and most need calcium to build skeletons and shells. The clam, like all sea creatures, gets its sodium and calcium from seawater salt. When the creatures die, their salt is locked up in sediment. Some of the sediment gets pushed deep within Earth-more about that in a moment.

The reactions between seawater and rocks are not one way. Sea salt not only dissolves from rocks, it also reacts with the sea rocks and rocks of the ocean crust and volcanic lava. The reactions remove some of the dissolved salts from the sea.

Plate tectonics explains the last mechanism for a balanced state of ocean saltiness. The outer hard crust of Earth consists actually of a dozen or so distinct, hard plates that drift individually on hot, deformable rock like floating islands on a sea. An unequal distribution of heat within Earth moves the plates much as marshmallows move on simmering cocoa.

When an ocean plate collides with a continental one, the less dense continental plate floats over the ocean one. The ocean floor gets pushed under, in the process, and at least half its mineral-rich, salty sediments end up lost deep within Earth.

Answer 4

All water, both fresh and sea water, contains dissolved chemicals in the form of salts. Water is considered fresh or salty according to individual taste, but detailed measurements prove otherwise, since even rain water contains a small concentration of salt that it absorbs while falling through the atmosphere.

Sea water is composed of, by weight, a mixture of approximately 96.5% pure water molecules (H2O molecules in diagram) and 3.5% of salts, dissolved gases, organic materials, and undissolved particles.

The salty taste associated with sea water comes from the two of the most common ions in the salt, chloride (Cl-) and sodium (Na+), which are surrounded by water (H2O) molecules in the diagram above.

(Remember that ions are atoms or combinations of atoms with charges, either negative or positive, depending on the difference in the number of electrons and protons; ions with more protons than electrons will result in a positive charge, more electrons than protons will produce a negative charge).

Indeed, the oceans may contain as much as 50 quadrillion tons (50 million billion tons) of dissolved solids, which if removed, would spread evenly over the Earth's land surface in the form of a layer more than 500 feet thick, about the height of a 40-story office building -- "now that's a lotta salt"..

Answer 5

Sea water has been defined as a weak solution of almost everything. Ocean water is indeed a complex solution of mineral salts and of decayed biologic matter that results from the teeming life in the seas. Most of the ocean's salts were derived from gradual processes such the breaking up of the cooled igneous rocks of the Earth's crust by weathering and erosion, the wearing down of mountains, and the dissolving action of rains and streams which transported their mineral washings to the sea. Some of the ocean's salts have been dissolved from rocks and sediments below its floor. Other sources of salts include the solid and gaseous materials that escaped from the Earth's crust through volcanic vents or that originated in the atmosphere.

Answer 6

Because many rivers end up in a sea and all those rivers will have been from various regions.Each region contains different type of soil.Those soils contain many different minerals and different salts.All those minerals would have got dissolved in the rivers and thus the rivers from those regions contain those dissolved minerals and salts.When the rivers join the sea,the sea water becomes salty.

Answer 7

Sea water is salty because rivers which join the sea contain salt which they get from the rocks as rocks are nothing but minerals.

Answer 8

hey! frnd it's easy to answer as the water of sea emerges from the mountains which contain several salts,that's a fact, and when this water gets into the water bodies like seas or oceans it's salty.

Answer 9

Its got nothing to do with science. But they say an Old story on it. The man had recited some spell for the preperation of salt near the banks. However he got the salt, but he did now the spell to stop the production of salt. As a result the salt is still flowing into the Oceans.

Answer 10

sea water is salty due to presence of natural calcium and phosphate salts and if u will ask how calcium and phosphate salts are present then i will have to say that this a natural phenomenon