Have you ever noticed that, in the summer, when your sweat dries it will leave marks on your T-shirt? The marks are tiny bits of salt.
If you go to the seaside, you will know that seawater does the same to your clothes, because it also has a lot of salt in it.
Water evaporates from the surface of the sea but the salt remains. Have you ever thought about whether the seas will keep getting saltier? The answer is no. The oceans have stayed at about 3.5 per cent salt content for hundreds of millions years. It maintains a constant level of salt in different ways.
evaporate v. 蒸發(fā)
Pick up a clamshell and weigh it in your hand. It is heavy. All creatures need sodium to live and most need calcium to build bones and shells. The clam, like all sea creatures, gets its sodium and calcium from seawater. When creatures die, their salt is locked up in bones and shells, which drop to the bottom of the sea.
clamshell n. 蛤殼 sodium n. 鈉 calcium n. 鈣 clam n. 蛤
Reactions between seawater and rocks are not just one way. Sea salt not only dissolves from rocks, it also reacts with the rocks of the ocean crust and volcanic lava. The reactions take some of the salts in seawater away from the sea.
dissolve v. 溶解 react v. 起反應(yīng) crust n. 外殼 lava n. 熔巖
The outer hard crust of Earth is made up of a dozen or so hard plates that drift on extremely hot, soft rock like floating islands on a sea. The heat within Earth is not the same everywhere and the plates move due to the heat.
drift v. 漂流
When an ocean plate bumps into a land plate, the less dense land plate floats over the ocean one. The ocean floor gets pushed under, and its salty rocks, along with shells and bones, are lost deep within Earth.
dense adj. 密集的 float v. 漂浮
So, that's why the seas are salty but don't get any saltier.
中文：
你有沒有注意到，夏天的時候，汗水干了之后會在T恤衫上留下一些痕跡？其實，這些痕跡是由極少量的鹽留下來的。
海水含有大量的鹽分，因此也會在人的身上留下同樣的痕跡。
海水蒸發(fā)掉了，而鹽留在了海里。你有沒有想過海水會變得越來越咸？答案是否定的。億萬年以來，海洋的鹽度始終保持在3.5%左右。海洋恒定的鹽度是由諸多原因造成的。
撿起一個蛤殼，在手里掂量一下它有多重。感覺很重。一切生物的生存都需要鈉，而且大部分生物都需要鈣質(zhì)來生成骨骼和貝殼。如同所有的海洋水族一樣，蛤從海水里攝取鈣質(zhì)。而水族們死后沉入海底，它們體內(nèi)的鹽分就被固定在骨骼和貝殼里。
海水和巖石之間的化學(xué)反應(yīng)并非是單向的。巖石溶解產(chǎn)生海鹽，而同時，海鹽又與大洋地殼中的巖石和火山熔巖進行化學(xué)反應(yīng)，從而把一部分鹽分從海水中帶走。
地球外部的堅硬外殼由大約12個板塊構(gòu)成。就像在海上漂流的島嶼一樣，這些板塊在極端高溫的地下巖漿上漂移。地球內(nèi)部的熱量在各個地方不均勻，由此導(dǎo)致了板塊運動。
當(dāng)大洋板塊與大陸板塊碰撞時，稍薄的大陸板塊就會漂在大洋板塊之上。這樣，大洋底受到了擠壓，含有鹽分的巖石，連同生物的貝殼和骨骼，被埋在了地球深處。
所以，這就是咸的海洋不會變得更咸的原因。
If you go to the seaside, you will know that seawater does the same to your clothes, because it also has a lot of salt in it.
Water evaporates from the surface of the sea but the salt remains. Have you ever thought about whether the seas will keep getting saltier? The answer is no. The oceans have stayed at about 3.5 per cent salt content for hundreds of millions years. It maintains a constant level of salt in different ways.
evaporate v. 蒸發(fā)
Pick up a clamshell and weigh it in your hand. It is heavy. All creatures need sodium to live and most need calcium to build bones and shells. The clam, like all sea creatures, gets its sodium and calcium from seawater. When creatures die, their salt is locked up in bones and shells, which drop to the bottom of the sea.
clamshell n. 蛤殼 sodium n. 鈉 calcium n. 鈣 clam n. 蛤
Reactions between seawater and rocks are not just one way. Sea salt not only dissolves from rocks, it also reacts with the rocks of the ocean crust and volcanic lava. The reactions take some of the salts in seawater away from the sea.
dissolve v. 溶解 react v. 起反應(yīng) crust n. 外殼 lava n. 熔巖
The outer hard crust of Earth is made up of a dozen or so hard plates that drift on extremely hot, soft rock like floating islands on a sea. The heat within Earth is not the same everywhere and the plates move due to the heat.
drift v. 漂流
When an ocean plate bumps into a land plate, the less dense land plate floats over the ocean one. The ocean floor gets pushed under, and its salty rocks, along with shells and bones, are lost deep within Earth.
dense adj. 密集的 float v. 漂浮
So, that's why the seas are salty but don't get any saltier.
中文：
你有沒有注意到，夏天的時候，汗水干了之后會在T恤衫上留下一些痕跡？其實，這些痕跡是由極少量的鹽留下來的。
海水含有大量的鹽分，因此也會在人的身上留下同樣的痕跡。
海水蒸發(fā)掉了，而鹽留在了海里。你有沒有想過海水會變得越來越咸？答案是否定的。億萬年以來，海洋的鹽度始終保持在3.5%左右。海洋恒定的鹽度是由諸多原因造成的。
撿起一個蛤殼，在手里掂量一下它有多重。感覺很重。一切生物的生存都需要鈉，而且大部分生物都需要鈣質(zhì)來生成骨骼和貝殼。如同所有的海洋水族一樣，蛤從海水里攝取鈣質(zhì)。而水族們死后沉入海底，它們體內(nèi)的鹽分就被固定在骨骼和貝殼里。
海水和巖石之間的化學(xué)反應(yīng)并非是單向的。巖石溶解產(chǎn)生海鹽，而同時，海鹽又與大洋地殼中的巖石和火山熔巖進行化學(xué)反應(yīng)，從而把一部分鹽分從海水中帶走。
地球外部的堅硬外殼由大約12個板塊構(gòu)成。就像在海上漂流的島嶼一樣，這些板塊在極端高溫的地下巖漿上漂移。地球內(nèi)部的熱量在各個地方不均勻，由此導(dǎo)致了板塊運動。
當(dāng)大洋板塊與大陸板塊碰撞時，稍薄的大陸板塊就會漂在大洋板塊之上。這樣，大洋底受到了擠壓，含有鹽分的巖石，連同生物的貝殼和骨骼，被埋在了地球深處。
所以，這就是咸的海洋不會變得更咸的原因。