Why is Earth filled with salt water?

Answer 1

earth is mostly covered with oceans, which may contain the carbonates and chlorides deposits which make it's water salty. On continents rock salt(Halite) is abundant which make the water saline.

Answer 2

Water is an excellent solvent. Many things we use every day rely on this fact (e.g. soda pop is basically water with sugar and carbon dioxide dissolved in it, bleach is water with sodium hypochlorite dissolved in it, etc).

Most salts, including ordinary table salt (sodium chloride) dissolve very well in water, and salt occurs naturally in rocks, so it's really no surprise that the oceans are salty. The surprising thing is that lakes and rivers aren't. This is because the water from lakes and rivers comes from rainfall: water vapor in the air condensing back into liquid droplets.

When water evaporates most things that were dissolved in the water (e.g. salt) are left behind, which leads to salt-free rain, and high concentrations of salt in any body of water in which the only way water leaves is by evaporation. This includes not only oceans, but also a number of so-called salt lakes where there is no significant river or stream flowing out of the lake. The dead sea in the Middle East is a good example of this.

Answer 3

because salt come from rocks as rivers come down into the sea they collect salt from rocks

Answer 4

they grow onions the same way we do just in a Greenhouse if they live in a cold place like england.