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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.
This does not mean, however, that the oceans’ saltiness is constantly increasing. Scientists believe that ocean salinity reached a plateau hundreds of millions of years ago, when roughly the same amount of salt fed into the oceans was deposited as sediment on the ocean floor.
咸的海水
親愛(ài)的《科學(xué)一刻》
我知道為什么海洋依舊是咸的了：水分蒸發(fā)掉，留下了鹽。但是一開(kāi)始鹽是怎么進(jìn)去的呢？——咸味雞尾酒
有種假設(shè)，海洋在至少五億年前形成。那時(shí)水蒸氣和其他氣體漸漸從地球內(nèi)部逸出，形成了圍繞地球的大氣層和云。當(dāng)?shù)厍蚶鋮s到水沸點(diǎn)以下，開(kāi)始下雨，下了好幾個(gè)世紀(jì)。最后，雨水填滿了地球的低洼形成了海洋。
地球的鹽
在海洋形成初期，它們還不像今天這樣咸。最初的雨席卷地球表面后匯入低洼，激流帶進(jìn)去了地殼腐蝕處的化學(xué)成分。這些化學(xué)成分包括鈉，那正是鹽的主要成分。另一個(gè)主要成分，氯，來(lái)自陸上海底火山噴發(fā)產(chǎn)生的塵土及氣體。經(jīng)過(guò)數(shù)億年，富含化學(xué)物質(zhì)的河流、陸上海底的火山噴發(fā)物，合在一起增加了海洋的鹽分。
然而，這并不意味著海洋會(huì)持續(xù)變咸下去?？茖W(xué)家認(rèn)為，海洋鹽度在數(shù)億年前就達(dá)到平穩(wěn)，當(dāng)時(shí)鹽注入海洋后，在海底形成了大體等量的沉積物。
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.
This does not mean, however, that the oceans’ saltiness is constantly increasing. Scientists believe that ocean salinity reached a plateau hundreds of millions of years ago, when roughly the same amount of salt fed into the oceans was deposited as sediment on the ocean floor.
咸的海水
親愛(ài)的《科學(xué)一刻》
我知道為什么海洋依舊是咸的了：水分蒸發(fā)掉，留下了鹽。但是一開(kāi)始鹽是怎么進(jìn)去的呢？——咸味雞尾酒
有種假設(shè)，海洋在至少五億年前形成。那時(shí)水蒸氣和其他氣體漸漸從地球內(nèi)部逸出，形成了圍繞地球的大氣層和云。當(dāng)?shù)厍蚶鋮s到水沸點(diǎn)以下，開(kāi)始下雨，下了好幾個(gè)世紀(jì)。最后，雨水填滿了地球的低洼形成了海洋。
地球的鹽
在海洋形成初期，它們還不像今天這樣咸。最初的雨席卷地球表面后匯入低洼，激流帶進(jìn)去了地殼腐蝕處的化學(xué)成分。這些化學(xué)成分包括鈉，那正是鹽的主要成分。另一個(gè)主要成分，氯，來(lái)自陸上海底火山噴發(fā)產(chǎn)生的塵土及氣體。經(jīng)過(guò)數(shù)億年，富含化學(xué)物質(zhì)的河流、陸上海底的火山噴發(fā)物，合在一起增加了海洋的鹽分。
然而，這并不意味著海洋會(huì)持續(xù)變咸下去?？茖W(xué)家認(rèn)為，海洋鹽度在數(shù)億年前就達(dá)到平穩(wěn)，當(dāng)時(shí)鹽注入海洋后，在海底形成了大體等量的沉積物。