How come the earth is 90% water and why is the ocean salty?

Answer 1

1) The earth's surface is roughly 70% water. This is because hydrogen and oxygen were once some of the most common elements in the atmosphere.

2) The ocean is salty because all rivers a slightly salty, because of the salt washed out from the soil. It gets washed down-river into the sea - but when it gets there it does not travel back up to the water source like the water does via evaporation, so it just stays in the sea. The effect of this over millions of years causes the sea (and other large bodies of water) to be salty.

Answer 2

More specifically the Earth's SURFACE is mostly water (closer to 70 percent than 90 percent, though). Which brings us to a simple reason, water is common, and it is lighter than the rocks and dirt and minerals that make up the land, and therefore floats above as much of the solid land that it can cover. If the Earth was smoother, it would be completely covered with water. Which brings us to more questions: why is there the particular amount of water that exists on earth? (don't know) and why isn't the Earth completely smooth (don't know either).

As for the ocean's saltiness, freshwater draining into the ocean carries a small amount of salt and other minerals into the ocean, which has built up over time. The ocean floor also leaches out salt and absorbs salt over time. The reaction with the ocean floor is what keeps the amount of salt in the ocean relatively constant.

Answer 3

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. 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. 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.

Answer 4

The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid (which forms from carbon dioxide and water). The rain erodes the rock and the acid breaks down the rocks and carries it along in a dissolved state as ions. The ions in the runoff are carried to the streams and rivers to the ocean. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not used up and are left for long periods of time where their concentrations increase over time.

The two ions that are present most often in seawater are are chloride and sodium. These two make up over 90% of all dissolved ions in seawater. By the way, the concentration of salt in seawater (salinity) is about 35 parts per thousand. In other words, about 35 of 1,000 (3.5%) of the weight of seawater comes from the dissolved salts; in a cubic mile of seawater the weight of the salt, as sodium chloride, would be about 120 million tons. And, just so you don't think seawater is worthless, a cubic mile of it also can contain up to 25 tons of gold and up to 45 tons of silver! Before you go out and try alchemy on seawater, though, just think about how big a cubic mile is.

By some estimates, if the salt in the ocean could be removed and spread evenly over the Earth’s land surface it would form a layer more than 500 feet (166 m) thick, about the height of a 40-story office building.

Link:
http://ga.water.usgs.gov/edu/earthhowmuch.html

Answer 5

The earth is not 90 percent water it is 70 percent water and the oceans are salty from all of the whale sperm that is in the water.

Answer 6

earth consists large bodies of water about 90% &10% land

Answer 7

Actually, the earth is not 90% water.

It is mostly iron, oxygen, silicon, magnesium, and nickel.
http://seds.lpl.arizona.edu/nineplanets/nineplanets/earth.html

I think what you are thinking about it that the earth's surface is 75% water (or around that percentage).