海盐的形成【阅读听力】

早早

Salty Seas

Dear A Moment of Science,

I know why the ocean is still salty: evaporated water leaves the salt behind. But how did it get salty in the first place?”—Salty Dog

According to one hypothesis, oceans formed at least 500 million years ago when water vapor and other gasses escaping from the Earth’s interior gradually formed the atmosphere and clouds surrounding the planet. As the earth cooled below the boiling point of water, rain began to fall, and kept falling for centuries. Eventually the rainfall filled the Earth’s hollows and formed oceans.

Salt of the Earth

In their infant state these oceans were not nearly as salty as they are today. As the initial rains swept over the planet’s surface and filtered down to the hollows, the rushing waters picked up chemicals from erosion of the Earth’s crust. These chemicals included sodium, which is one of the main ingredients of salt. The other main ingredient, chlorine, came from the solid and gaseous fallout of land and ocean floor volcanoes. Over hundreds of millions of years the steady flow of chemical-rich rivers and streams and the eruption of volcanoes and undersea vents combined to increase the oceans’ salt content.

译文：

在海洋形成初期，它们还不像今天这样咸。最初的雨席卷地球表面后汇入低洼，激流带进去了地壳腐蚀处的化学成分。这些化学成分包括钠，那正是盐的主要成分。另一个主要成分，氯，来自陆上海底火山喷发产生的尘土及气体。经过数亿年，富含化学物质的河流、陆上海底的火山喷发物，合在一起增加了海洋的盐分。

然而，这并不意味着海洋会持续变咸下去。科学家认为，海洋盐度在数亿年前就达到平稳，当时盐注入海洋后，在海底形成了大体等量的沉积物。

【本译文由普特网友 bydavia 提供】