海はどうしてしょっぱい？ 青く見えるのはなぜ？ 深いところはどうなっているの？
左にしつもん、右にこども向けせつめい。広い海のひみつを、やさしく見てみよう。
Why is the sea salty? Why does it look blue? What is it like deep under the water?
Questions on the left, easy answers on the right. Let’s gently explore the secrets of the big, wide sea.
🌊うみの色Sea color🐬いきものSea life⚓うみの旅Sea trip🌏地球と水Earth & water
1QUESTION
どうして海はしょっぱいの？Why is the sea salty?
川の水はしょっぱくないのに…。River water is not salty, but sea water is. Why?
その塩分が長い時間かけて海にたまって、しょっぱい水になっているんだよ。
Sea water has a lot of salt dissolved in it.
As rain, rivers, and sea water keep going around and around,
a little bit of salt from rocks and soil mixes into the water.
Over a very long time, this salt builds up in the sea,
so the sea tastes salty.
🧂海水をゆっくり煮つめると、白い塩が出てくるよ。If you boil sea water slowly, white salt will remain after the water is gone.
だから遠くから見ると、海は青く見えるんだよ。
The sea is a very deep and wide world of water.
When sunlight goes into the sea, red and yellow light are taken in easily,
and more of the blue light comes back to our eyes.
That’s why, when we look from far away, the sea looks blue.
👀近くで見ると透明なのに、遠くで見ると青い！ 海の「見え方」のふしぎだね。Near you, water can look clear, but far away the sea looks blue. That’s a fun “how it looks” mystery.
3QUESTION
海はどれくらい深いの？How deep is the sea?
下まで見えないほどの深さ！It’s so deep we can’t see the bottom!
1番深い海は1万メートル以上あるといわれているよ！
The seas of the world have very different depths in different places.
In shallow places, an adult can stand with just their legs in the water.
But in the deepest places, it’s deep enough to fit a building taller than a big mountain.
The deepest part of the sea is said to be over 10,000 meters deep!
🌐海は「高い山をまるごと入れても足りない深さ」がある世界なんだ。The sea is a world so deep that even a very tall mountain could fit inside it.
4QUESTION
どうして海の波はいつも動いているの？Why are sea waves always moving?
大きな波は、強い風や台風でできることが多いよ。
Waves are made by the pushing force of the wind on the sea.
Sea water is connected in a big, wide area, so when the wind blows,
the water moves up and down and becomes waves.
Very big waves often come from strong winds or typhoons.
🌬️おふろの水に息をフッとかけると小さな波が立つ。それと少し似ているね。If you blow on bath water, you’ll see small waves. That’s a bit like what wind does to the sea.
5QUESTION
海にはどれくらい生き物がいるの？How many living things are in the sea?
海は地球最大のいのちの家なんだ。
There are so many living things in the sea that we cannot count them all!
Not only fish and crabs, but also jellyfish, dolphins, and whales,
and many tiny baby living things too.
The sea is the biggest home of life on Earth.
🐙図鑑や水族館で、海の生き物をさがしてみよう。名前と形をメモすると楽しいよ。Look for sea animals in books or at an aquarium. It’s fun to write down their names and shapes.
6QUESTION
海の水はどこへ行くの？Where does the sea’s water go?
海はなくならないの？Will the sea ever run out of water?
ANSWER
海の水は、太陽の力で空へ上って雲になり、
やがて雨や雪になって、また海や川へもどってくるんだ。
地球は水をぐるぐる回して生き物を守っているんだよ。
Sea water rises up into the sky with the help of the Sun,
becomes clouds, and later falls as rain or snow.
The water then goes back to rivers and the sea.
Earth protects life by keeping water moving in a big cycle.
💧「水の旅」を世界地図でたどってみると、海どうしのつながりが見えてくるよ。Follow the “journey of water” on a world map, and you’ll see how the seas are connected.
7QUESTION
潮の満ち引きはどうして起きるの？Why do tides go in and out?
海辺で水の高さが変わるふしぎ。At the shore, the water level keeps changing. Why?
これが満ち引き（みちひき）とよばれるふしぎな動き！
The sea’s water is pulled by the gravity of the Moon.
The water is pulled closer in some places and moves away in others,
so the water level goes up and down.
This up-and-down movement is the tide, called “high tide” and “low tide.”
🌙海辺の岩場に行くと、朝と昼で水の位置がどれくらいちがうか見くらべてみよう。At the seashore, compare where the water reaches in the morning and at noon. You’ll see the tide change.
8QUESTION
なぜ海はこんなに広いの？Why is the sea so wide?
地球の大部分が海！Most of Earth’s surface is sea!
ANSWER
地球が生まれたとき、たくさんの水が地表に集まったんだ。
その水が広がって、今の大きな海をつくった。
今では、地球の表面のだいたい7わりは海なんだよ！
When Earth was young, a lot of water gathered on its surface.
That water spread out and became today’s huge seas and oceans.
Now, about 70% of Earth’s surface is covered by the sea!
🌏地球儀を見て、「青いところ」と「陸のところ」をくらべてみよう。海の広さがすぐ分かるよ。Look at a globe and compare the blue parts with the land parts. You’ll quickly see how wide the sea is.
9QUESTION
海には、どんな「つぎの なぜ？」があるかな？What other “whys” about the sea can you think of?
好奇心は海より深い！Your curiosity can be deeper than the sea!
IDEAS
たとえば、こんな疑問も考えられるよ：
どうして深海はまっくらなの？
海の底はどうやって調べるの？
海に住む生き物はどうやって息をするの？
海はひとつにつながっているの？
For example, you might ask:
Why is the deep sea completely dark?
How do people study the bottom of the sea?
How do sea animals breathe under water?
Are all the seas of the world connected?
🔍水族館・図鑑・地図を使って、「海のつづき」を見てみよう。海のナゾはまだまだあるよ。Use aquariums, books, and maps to look for “more of the sea.” There are still many sea mysteries to explore.