First, the good news. Water, the source of all life on Earth, is abundant. Now, the bad news. Most of it is undrinkable. Ninety-seven percent of the water on our planet is salty and 2% is frozen as ice at the poles, leaving a measly 1% for people to use. How is it, you may wonder, that so much of the liquid water on our planet is salty?
abundant [ əˈbʌndənt ] a. 豐富的，充足的 measly [ ˈmizlɪ ] a. 少少的
Water is a compound of two hydrogen atoms and one oxygen atom: H2O. When water on the Earth’s surface evaporates as water vapor, it picks up tiny amounts of two gases found in the Earth’s atmosphere, carbon dioxide and sulphur dioxide. When this vapor forms raindrops, this “fresh” water is actually slightly acidic.
evaporate [ ɪˈvæpəˌret ] vi. 蒸發 vapor [ ˈvepɚ ] n. 水蒸氣 acidic [ əˈsɪdɪk ] a. 酸性的 acid [ ˈæsɪd ] n. 酸性物質
As it falls on the ground, the acid dissolves small amounts of mineral salts, which end up in the water, a process known as weathering. These tiny amounts of salts have built up for billions of years, producing our salty oceans. Volcanic activity also contributes to the saltiness of the ocean in similar ways.
mineral [ ˈmɪnərəl ] n. 礦物質 weather [ ˈwɛðɚ ] vi. & vt.（使）（岩石、木頭等）風化／受風雨侵蝕（本文為動名詞用法） saltiness [ ˈsɔltɪnɪs ] n. 鹹度
Most of us have accidentally gulped a bit of sea water and tasted its salt. You wouldn’t want that to happen while floating or swimming in the Dead Sea—its water is nearly 10 times as salty as that* found in the ocean! Only a few microbes can stand so much salinity. Still, all those minerals are supposed to be good for healthy skin. We can’t drink it, but we can still bathe and swim in it.
