The beginning一開始
Let it play. The water circles, and the white cubes begin to collect.
讓它播放。水繞著圈，白色的小方塊開始累積。
Earth and Weather · Unit 3 · Lesson 13 · 地球與天氣 單元三 第十三課
Why Is the Sea Salty?海水為什麼是鹹的？
Rain is not salty. Rivers are not salty. Yet all the rivers in the world run into the sea, and the sea is very salty. Where does the salt come from? In a 3D model, follow water as it goes around and around, and watch what happens to the salt it carries. Then work out how much salt is hiding in a bucket of seawater, and visit the old salt fields of Lukang.
雨水不鹹，河水也不鹹。可是全世界的河都流進海裡，海水卻非常鹹。鹽是從哪裡來的？在 3D 模型裡，跟著水一圈一圈地繞，看看它帶著的鹽後來怎麼了。然後算一算一桶海水裡藏了多少鹽，再去看看鹿港以前的鹽田。
Big idea · 一句話看懂
Water travels in a circle, but salt travels one way. Rain dissolves a tiny bit of rock, and rivers carry that tiny bit down to the sea. When the sun warms the sea, only the water rises into the air. The salt cannot follow, so it stays behind. Over a very long time, the tiny bits added up, and the sea became salty.
水走的是一個圈，鹽走的卻是單行道。雨水會溶掉一點點岩石，河流再把這一點點帶到海裡。太陽把海水曬暖的時候，只有水升到空中；鹽跟不上去，就留了下來。經過非常非常久的時間，這些一點點加在一起，海水就變鹹了。
3D Model · 3D 模型
Water Goes Around, Salt Stays 水一直繞，鹽留下來
Drag to turn the model, and scroll or pinch to zoom. The blue dots are water. Follow them down the river, across the sea, up into the air, over to the cloud, and down again as rain. The white cubes are salt. Follow them too. Where do they stop? Move the time slider and watch the sea. Then send the river into a lake that has a way out, and see what changes.
拖曳可以旋轉模型，滾輪或雙指可以縮放。藍色的點是水。跟著它們順著河流下去、越過海面、升到空中、飄到雲裡，再變成雨落下來。白色的小方塊是鹽，也跟著它們看看：它們停在哪裡？撥動時間滑桿，注意海的變化。接著讓河流流進一個有出口的湖，看看有什麼不一樣。
Drag to turn · 拖曳旋轉 Scroll or pinch to zoom · 滾輪／雙指縮放
This 3D model needs WebGL, which this browser does not support. The reading and the cards below still explain everything.
這個瀏覽器不支援 WebGL，無法顯示 3D 模型；下方的課文與卡片一樣能看懂。
- Blue dots: water
藍色的點：水 - Small gray-blue dots rising: water vapor
往上升的灰藍色小點：水氣 - White cubes: salt
白色小方塊：鹽
A teaching model. The 3.5% for today's sea is a real figure. Everything about time is only a picture: the real sea took an enormous length of time to become salty, and the curve in the model was drawn to show the idea. The model shows only the main source of salt, the rivers. Some salt also comes from hot springs and volcanoes on the seabed. River water does carry dissolved minerals, but far too few to taste.
這是教學用的模型。今天的海水鹽度 3.5% 是真的數字。和「時間」有關的部分都只是示意：真的海花了極長的時間才變鹹，模型裡的曲線是為了說明原理畫的。模型只畫了鹽最主要的來源，也就是河流；另外還有一些鹽來自海底的熱泉和火山。河水裡確實溶有礦物質，只是少到嘗不出來。
Model drawn by My Culture Connect as a teaching diagram. The ideas follow the U.S. National Ocean Service page Why is the ocean salty? and the other sources listed at the bottom of this page. · 模型由人師教育協會自繪示意；原理依美國國家海洋局「Why is the ocean salty?」與本頁最下方列出的其他出處。
Reading · 英文閱讀
13
Unit 13: Why Is the Sea Salty?
If you have ever swallowed a mouthful of seawater, you know how salty it is. But the rain that falls into the sea is not salty, and neither are the rivers that run into it. So how did the sea get its salt? The answer is a slow story, and it begins on land.
如果你曾經不小心喝到一口海水，就知道它有多鹹。可是落進海裡的雨水並不鹹，流進海裡的河水也不鹹。那海裡的鹽是怎麼來的？答案是一個很慢很慢的故事，而且要從陸地上說起。
Rainwater can dissolve rock. It does this very, very slowly, but it never stops. As rain runs over the ground and soaks through it, it picks up tiny amounts of minerals. Streams carry these minerals to rivers, and rivers carry them to the sea. There is so little in a river that you cannot taste it at all.
雨水會溶解岩石。它溶得非常非常慢，但是從來不停。雨水流過地面、滲進土裡的時候，會帶走極少量的礦物質。小溪把這些礦物質帶到河裡，河流再把它們帶到海裡。河水裡的礦物質少到你完全嘗不出來。
Now think about what happens next. The sun warms the sea, and water rises into the air as vapor. But only the water rises. The minerals cannot turn into vapor, so they stay in the sea. The vapor becomes cloud, the cloud becomes rain, and the rain washes a little more out of the rocks. The water goes around again and again. The salt makes the trip only once.
接下來想一想會發生什麼事。太陽把海水曬暖，水變成水氣升到空中。可是升上去的只有水。礦物質沒辦法變成水氣，所以留在海裡。水氣變成雲，雲變成雨，雨又從岩石裡洗出一點點。水就這樣一圈又一圈地繞；鹽卻只走這麼一趟。
This has been going on for an enormous length of time, and tiny amounts add up. Today, about 3.5% of the weight of seawater is salt. If you dried up one liter of seawater, about 35 grams of salt would be left. Most of it is the same kind of salt that we put on food.
這件事已經持續了極長的時間，一點點累積起來就很可觀。今天，海水的重量裡大約有 3.5% 是鹽。把一公升的海水曬乾，大約會剩下 35 公克的鹽。其中大部分，就是我們加在食物裡的那種鹽。
Is the sea still getting saltier? Scientists think that it is not. Salt leaves the sea too, very slowly. Some is used by living things, and some ends up buried in the seabed. For a very long time, about as much salt has left as has arrived, so the sea has stayed about the same.
海水還在繼續變鹹嗎？科學家認為沒有。鹽也會離開海水，只是非常慢：有些被生物用掉，有些最後被埋進海底。很久很久以來，離開的鹽和進來的鹽差不多一樣多，所以海水的鹹度大致沒有變。
People have used this for a very long time. If the sun can lift water out of the sea and leave the salt behind, then we can let the sun make salt for us. Let seawater into a shallow pond, wait for the sun and the wind to dry it, and collect what is left. Taiwan made salt this way for more than three hundred years, on the sunny coast of the southwest and, for a time, at Lukang in Changhua.
人們很早就懂得利用這件事了。既然太陽可以把水從海裡帶走、把鹽留下來，那就可以讓太陽來幫我們做鹽。把海水引進淺淺的池子，等太陽和風把它曬乾，再把剩下的東西收起來。台灣用這個方法曬鹽曬了三百多年，主要在陽光充足的西南沿海；彰化的鹿港也曾經有過鹽田。
Read aloud · 課文朗讀
Questions · 閱讀理解
Where does the salt in the sea come from?
Rainwater slowly dissolves tiny amounts of minerals from rocks on land, and rivers carry them to the sea.
Why does the salt stay in the sea when the water leaves?
Water leaves the sea by turning into vapor. Salt cannot turn into vapor, so it stays behind.
How much salt is in one liter of seawater?
About 35 grams, which is about 3.5% of the weight of the water.
Words & Phrases · 生字及片語
salt(n.)鹽Please pass the salt.請把鹽遞給我。salty(adj.)鹹的Seawater is too salty to drink.海水太鹹了，不能喝。dissolve(v.)溶解Sugar dissolves in hot tea.糖會溶在熱茶裡。mineral(n.)礦物質Rocks are made of minerals.岩石是由礦物組成的。fresh water(n.)淡水Rivers and most lakes hold fresh water.河流和大部分的湖裡是淡水。seawater(n.)海水Seawater stings your eyes.海水會讓眼睛刺痛。taste(v.)嘗；嘗起來This soup tastes too salty.這碗湯嘗起來太鹹了。pond(n.)池子；池塘Salt is made in a shallow pond.鹽是在淺淺的池子裡做出來的。
Quick Check · 小測驗
1. Where does most of the salt in the sea come from?
2. What happens to the salt when seawater turns into vapor?
3. About how much salt is in one liter of seawater?
4. Why are most lakes not salty?
5. How do people get salt from the sea?
Work It Out · 算算看
How much salt is left? 曬乾之後剩多少鹽？
Choose a kind of water, choose how much of it to dry up, and see how much salt is left in the pan.
選一種水，再選要曬乾多少，看看盤子裡會剩下多少鹽。
1 · Which water? · 哪一種水？
A liter of water is counted here as one kilogram, which is close enough. One teaspoon of salt is taken to be about 6 grams. The Dead Sea figure is from 2011. Never taste water from the sea or from an experiment unless an adult says it is safe.這裡把一公升的水當成一公斤來算，差不了多少。一茶匙的鹽以大約 6 公克計。死海的數字是 2011 年的。沒有大人確認安全之前，不要嘗海水或實驗用的水。
Left in the pan · 盤子裡剩下
35 grams of salt · 公克的鹽
About 6 teaspoons · 大約這麼多茶匙
Try It in the Model · 在模型裡試試
Four moments 四個時刻
Watch one white cube all the way from the mountain. Does it ever go up into the cloud?
盯著一顆白色的小方塊，從山上一路看下來。它有沒有哪一次升到雲裡去？
Long ago很久以前
The sea already holds much more salt than any river.
海裡的鹽已經比任何一條河都多得多。
The sea today今天的海
Thirty-five grams in every liter, and holding steady.
每公升 35 公克，而且維持不變。
A lake with a way out有出口的湖
The same river, the same salt. But here the salt flows out again.
同樣的河，同樣的鹽，可是在這裡鹽又流出去了。
Go Further · 延伸閱讀
The water's round trip 水的來回旅程
Earth and Weather · Lesson 6 · 地球與天氣 第六課Why Does It Rain?為什麼會下雨？The upward half of the trip: from the sea to the cloud.旅程往上的那一半：從海到雲。Go to the lesson · 前往這一課 →Earth and Weather · Lesson 11 · 地球與天氣 第十一課How Do Rivers Shape the Land?河流怎麼改變大地？Rivers carry sand and mud that you can see, and minerals that you cannot.河流帶著你看得見的泥沙，也帶著你看不見的礦物質。Go to the lesson · 前往這一課 →
Salt by the Numbers · 鹽的數字
Six numbers about the salty sea 六個和鹹鹹的海有關的數字
From one liter of seawater to the last salt field in Taiwan.
從一公升的海水，到台灣最後一座鹽場。
3.5%salt · 是鹽
On average, about 3.5% of the weight of seawater is dissolved salt.平均來說，海水的重量裡大約有 3.5% 是溶在裡面的鹽。
35 gper liter · 每公升
Dry up one liter of seawater, and about 35 grams of salt are left.把一公升的海水曬乾，大約剩下 35 公克的鹽。
85%of it · 其中
Chloride and sodium, the two parts of ordinary table salt, make up about 85% of everything dissolved in the sea.溶在海水裡的東西，大約 85% 是氯和鈉，也就是一般食鹽的兩個成分。
97%of the water · 的水
The ocean holds about 97% of all the water on Earth. Nearly all of the world's water is salty.海洋裝著地球上大約 97% 的水。世界上幾乎所有的水都是鹹的。
34.2%salt · 是鹽
The Dead Sea, measured in 2011. That is almost ten times as salty as the ocean.這是死海 2011 年的鹽度，差不多是海水的十倍。
338years · 年
Taiwan made salt by drying seawater in the sun for this long. The last harvest was at the Qigu salt fields in Tainan in May 2002.台灣曬鹽的歷史有這麼長。最後一次收鹽，是 2002 年 5 月在台南的七股鹽場。
Salt Stories · 鹽的故事
Halley's idea, the Dead Sea, the salt fields of Lukang, and the last harvest 哈雷的想法、死海、鹿港的鹽田，還有最後一次收鹽
Four stories about where salt goes and where it stays.
四個故事，講鹽去了哪裡、又留在哪裡。
1715
Halley's idea哈雷的想法
Edmond Halley is famous for a comet, but he also thought about the sea. In 1715 he suggested that rain washes salt and other minerals out of the ground, that rivers carry them to the sea, and that they build up there as more arrives. Three hundred years later, that is still the heart of the answer.
哈雷最有名的是那顆彗星，不過他也想過海的問題。1715 年他提出：雨水把鹽和其他礦物質從土地裡洗出來，河流把它們帶到海裡，新的不斷加進來，就越積越多。三百年後，這仍然是答案的核心。
Lake · 湖
A lake with no way out沒有出口的湖
The Dead Sea lies in a hot, dry valley, and it is really a lake. A river flows in, but nothing flows out. The only way water can leave is by evaporating, so the salt has been collecting there, just as it does in the ocean. The lake is now almost ten times as salty as the sea, and a swimmer floats on it like a cork.
死海位在一個炎熱乾燥的谷地裡，它其實是一個湖。有河流進去，卻沒有任何水流出來。水唯一能離開的方法就是蒸發，所以鹽一直在那裡累積，和海洋的情形一樣。這個湖現在差不多是海水的十倍鹹，人在上面像軟木塞一樣浮著。
Changhua · 彰化
The salt fields of Lukang鹿港的鹽田
Lukang was once a busy port, but its harbor slowly filled with sand. In 1900, a businessman from Lukang named Koo Hsien-jung received permission to turn the tidal flats on the coast into salt fields. Others followed, and in 1914 Lukang was for a time the largest salt field in Taiwan. The land was not well suited to it, though. After a great flood in 1959 the fields were closed, and it took six years to wash the salt out of the soil so that it could be farmed.
鹿港曾經是熱鬧的港口，可是港灣漸漸淤淺了。1900 年，出身鹿港的辜顯榮獲准把沿海的海埔地開闢成鹽田。後來又有人跟著開闢，到了 1914 年，鹿港一度成為全台灣最大的鹽場。不過這裡的先天條件並不理想。1959 年八七水災之後，鹽田正式分期廢曬，花了六年才把土裡的鹽分洗掉，改成農田和魚塭。
2002
The last harvest最後一次收鹽
The largest salt fields in Taiwan were at Qigu, in Tainan. In May 2002 the workers there gathered salt for the last time, and more than three hundred years of making salt in the sun came to an end. The empty ponds did not stay empty for long. They have become wetlands, and many kinds of birds now live there.
台灣最大的鹽場在台南的七股。2002 年 5 月，那裡的鹽工最後一次收鹽，三百多年的曬鹽歷史就此結束。空下來的鹽田並沒有空很久：它們變成了濕地，現在是許多鳥類棲息的地方。
Myth vs. Fact · 常見迷思
Four things people get wrong 四個常見的誤會
✗ Myth · 迷思Rivers are fresh, so they cannot be where the salt comes from.河水是淡的，所以鹽不可能是河流帶來的。
✓ Fact · 事實Rivers carry a tiny amount of dissolved minerals, too little to taste. It has been arriving for an enormous length of time, and it does not leave when the water evaporates.河水裡溶有極少量的礦物質，少到嘗不出來。可是它流了極長的時間，而且水蒸發的時候，這些東西不會跟著離開。
✗ Myth · 迷思When seawater evaporates, the rain that falls later is salty.海水蒸發以後，下的雨也是鹹的。
✓ Fact · 事實Only the water turns into vapor. The salt stays in the sea, so rain is fresh.只有水會變成水氣，鹽留在海裡，所以雨水是淡的。
✗ Myth · 迷思The sea gets saltier every year.海水一年比一年鹹。
✓ Fact · 事實Scientists think its saltiness has stayed about the same for a very long time, because salt also leaves the sea slowly.科學家認為海水的鹹度很久以來大致沒有變，因為鹽也會慢慢地離開海水。
✗ Myth · 迷思If you are thirsty at sea, you can drink a little seawater.在海上口渴的時候，可以喝一點海水。
✓ Fact · 事實Seawater is far too salty for the human body. Never drink it.海水對人體來說太鹹了。絕對不要喝。
Remember It · 記憶口訣
The salty sea in a sentence 一句話記住海水為什麼鹹
Rain dissolves rock雨水溶掉岩石
Only a tiny bit at a time.
一次只有一點點。
Rivers carry it down河流帶下去
Too little to taste.
少到嘗不出來。
Only water goes up只有水升上去
The salt stays behind.
鹽留了下來。
Tiny bits add up一點點會累積
Thirty-five grams in a liter.
一公升裡有 35 公克。
Classroom Activity 1 · 課堂活動一
Make a Salt Field 做一塊小鹽田
You need · 準備材料
- A cup of warm water, two teaspoons of salt, and a spoon一杯溫水、兩茶匙的鹽，還有一支湯匙
- A dark plate or a dark baking tray, and a sunny windowsill一個深色的盤子或烤盤，還有一個曬得到太陽的窗台
Steps · 步驟
- Stir the salt into the warm water until you cannot see it anymore. Where did it go?把鹽攪進溫水裡，一直攪到看不見為止。鹽跑到哪裡去了？
- Pour a thin layer of the salty water onto the dark plate.把鹽水倒在深色的盤子上，薄薄一層就好。
- Leave the plate in the sun. Look at it every day, and do not touch it.把盤子放在太陽下。每天看一看，不要去動它。
- When the water is gone, look closely at what is left. What shape are the pieces?水不見了以後，仔細看看剩下的東西。它們是什麼形狀？
The water left as vapor, and the salt stayed. A magnifying glass will show you tiny cubes. A shallow layer dries much faster than a deep one, which is why salt ponds are so shallow.
水變成水氣走了，鹽留了下來。用放大鏡可以看到一顆顆小小的立方體。淺淺的一層比深的乾得快得多，所以鹽田的池子都做得很淺。
Classroom Activity 2 · 課堂活動二
Float an Egg 讓蛋浮起來
You need · 準備材料
- A tall glass of water and a raw egg in its shell一個裝了水的高杯子，還有一顆帶殼的生雞蛋
- Salt and a spoon鹽和湯匙
Steps · 步驟
- Lower the egg gently into the glass of fresh water. What does it do?把蛋輕輕放進裝著清水的杯子裡。它怎麼了？
- Take the egg out. Stir in one spoonful of salt until it dissolves, and try the egg again.把蛋拿出來。加一匙鹽，攪到溶化，再把蛋放進去試試看。
- Keep adding salt, one spoonful at a time. Count the spoonfuls until the egg floats.繼續一匙一匙地加鹽。數一數加到第幾匙，蛋才浮起來。
- Why is it easier to float in the sea than in a swimming pool?為什麼在海裡比在游泳池裡容易浮起來？
Salt makes water heavier for its size, so it pushes up harder on things. Wash your hands after you handle the raw egg, and do not eat the egg afterward.
鹽讓同樣體積的水變重，所以把東西往上推的力量比較大。摸過生雞蛋之後要洗手，這顆蛋之後也不要吃。
Sources · 資料出處
Facts and numbers on this page were checked against these sources (October 2026). · 本頁的事實與數字依下列資料查證（2026 年 10 月）。
- Rocks on land are the major source of salts in seawater: rainwater erodes rock, and streams and rivers carry the ions to the ocean; some are removed by living things; other sources include vents and volcanic eruptions on the seafloor; chloride and sodium make up about 85% of the dissolved ions; average salinity is about 35 parts per thousand, or 3.5% by weight陸地上的岩石是海水中鹽類的主要來源：雨水侵蝕岩石，溪流與河川把離子帶進海洋；一部分被生物利用而移除；其他來源包括海底熱泉與海底火山噴發；氯與鈉約占溶解離子的 85%；平均鹽度約千分之 35，即重量的 3.5%NOAA National Ocean Service, “Why is the ocean salty?” ↗
- Seawater holds about 35 grams of dissolved salts per liter; Halley proposed in 1715 that rivers carry salt washed from the ground into the sea, where it builds up; ocean salinity has been stable for a very long time because salt is removed about as fast as it is added每公升海水約含 35 公克溶解的鹽；哈雷在 1715 年提出鹽由河流從土地帶進海洋並逐漸累積；海洋鹽度長期穩定，因為鹽被移除的速度與加入的速度大致相當Wikipedia, “Seawater” ↗
- The ocean contains about 97% of Earth's water海洋約占地球水量的 97%Wikipedia, “Ocean” ↗
- The Dead Sea: a salinity of 34.2% in 2011, 9.6 times as salty as the ocean; a lake whose water leaves only by evaporation; swimmers float easily死海：2011 年鹽度 34.2%，是海洋的 9.6 倍；湖水只能靠蒸發離開；人很容易浮起來Wikipedia, “Dead Sea” ↗
- Sea salt is made by evaporating seawater in shallow ponds海鹽是在淺池中蒸發海水製成的Wikipedia, “Sea salt” and “Salt evaporation pond” ↗
- The Lukang salt fields: opened after Koo Hsien-jung received permission in 1900; for a time the largest in Taiwan in 1914; closed in stages after the flood of 1959, and it took six years to wash the salt from the soil鹿港鹽場：1900 年辜顯榮申請獲准後開闢；1914 年一度為全臺最大鹽場；1959 年八七水災後正式分期廢曬，共花了六年洗去鹽分維基百科「鹿港鹽場」 ↗
- The Qigu salt fields: the largest in Taiwan and the last to close; the final harvest in May 2002 ended 338 years of making salt in the sun; the land has become wetland where many birds live七股鹽場：臺灣最大、也是最後一個鹽場；2002 年 5 月最後一次收鹽，結束臺灣 338 年的曬鹽史；鹽田土地成為許多鳥類的棲息地（七股鹽田濕地）維基百科「七股鹽場」 ↗