Oceans and Land
FoundationOceans cover about seventy per cent of the Earth, more than land, and the atmosphere wraps the Earth like a coat — that is why Earth is called the Blue Planet.
- The Earth's surface has oceans and land.
- Oceans cover about seventy per cent — more than land.
- A globe is a model that helps us see oceans and land.
文體小知識：說明文把知識講得清清楚楚。這一篇帶你從太空照片和地球儀，認識海洋、陸地和包圍地球的大氣。
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1We all live on Earth. Earth is big and round, like a giant ball. In photos taken from space, most of the Earth is blue — that is the colour of the oceans. The green and yellow parts are land, where we live, grow crops and build cities. Learning about oceans and land opens the first page of knowing our Earth.
2Scientists have worked out that oceans cover about seventy per cent of the Earth's surface, while land covers only about thirty per cent. The oceans are huge and wide — the Pacific, the Atlantic and the Indian Ocean. On land there are mountains, plains, rivers and forests, as well as our cities and villages. Because oceans cover more than land, Earth is also called the Blue Planet.
3To see it clearly, we can look at a globe. A globe is a model of the Earth: blue stands for oceans, and other colours stand for land and countries. Turn the globe and you will find the blue parts are far bigger than the land. Astronauts looking at the Earth from space also see a huge blue ocean first — what a splendid sight.
4Around the Earth is an invisible layer of air called the atmosphere, like a protective coat. The atmosphere gives us air to breathe, blocks some harmful light from the sun, and burns up small rocks that fly towards the ground. With the atmosphere, the oceans and the land, the Earth becomes a wonderful home for people, animals and plants.
1Summary 重點摘要
Oceans cover about seventy per cent of the Earth, more than land, and the atmosphere wraps the Earth like a coat — that is why Earth is called the Blue Planet.
2Vocabulary cards Vocabulary
The planet we live on; big and round like a ball.
The huge salty water covering most of the Earth's surface.
The dry part of the Earth's surface, with mountains, plains and cities.
The outermost layer of something; the Earth's surface has oceans and land.
A model of the Earth that helps us see where oceans and land are.
The layer of air around the Earth, like a protective coat.
A person who travels into space and takes photos of the Earth.
Another name for the Earth, because oceans cover most of it.
To keep something safe from harm.
3Step by step Steps
- Step 1: Get to know our EarthWe all live on the Earth. The Earth is big and round, like a giant ball, but people, animals and plants live only on its surface. The surface is not the same everywhere: some parts are water, some are land, and above them are clouds and air. To know the Earth, start with photos taken from space, then turn a globe and look at the shapes of the land and oceans. Knowing the Earth is our first step in exploring the world, and it helps us treasure this beautiful home.
- Step 2: Study photos and a globePhotos of the Earth taken by astronauts are great learning materials. In the photos the Earth is round and mostly blue — the colour of the oceans; the green and brown parts are land, and the white parts are clouds. A globe is a model of the Earth: blue stands for oceans, and other colours stand for countries and land. Turn the globe and you will see the blue parts are much bigger than the land. Looking at photos and a model is like seeing the Earth from space, with oceans and land clear at a glance.
- Step 3: Oceans cover more than landScientists have worked out that oceans cover about seventy per cent of the Earth's surface, and land only about thirty per cent. In other words, if we split the surface into ten parts, about seven parts are ocean and only three are land. The oceans are huge and wide — the Pacific, the Atlantic, the Indian Ocean and more; the sea beside Hong Kong is only a tiny part of them. Since oceans cover more than land, the Earth looks like a blue planet from space — the oceans are its greatest feature.
- Step 4: What is on the landThough land is smaller than the oceans, it is where we live. On land there are mountains, plains, valleys and deserts, rivers and lakes running through, plus forests and grasslands full of plants. People build houses, schools and roads on land, forming cities and villages; animals and plants also find their homes there. In Hong Kong there are more hills than flat land, so most of our buildings and roads stand on the flat land along the coast. Knowing the land helps us see why we must plan for it and care for it.
- Step 5: The atmosphere — Earth's protective coatAround the Earth is a thick layer of air called the atmosphere. We cannot see or touch it, yet it is very important, like a protective coat for the Earth. It gives us air to breathe; it blocks some of the sun's harmful light and heat, keeping the Earth neither too cold nor too hot; and small rocks flying towards the Earth burn up in the atmosphere, protecting living things below. Without the atmosphere, the Earth would become a cold, dry and unfit place to live, and people, animals and plants could hardly survive.
- Step 6: The Blue Planet is our homeHaving learned about the oceans, the land and the atmosphere, we can see why the Earth is so special. Seen from space, oceans cover most of the surface, making the Earth a beautiful blue planet; on land there are mountains and plains that feed people, animals and plants; and outside, the atmosphere protects everyone like a coat. In the solar system, only the Earth has all these conditions for life. So we must know the Earth and care for it, keeping this blue planet beautiful as the shared home of us and generations to come.
5Worked example Example
Example: An astronaut takes photos of the Earth from space, and the planet looks mostly blue. Why do people call the Earth the Blue Planet?
- Looking at the Earth from space, the first thing we see is a huge stretch of blue — the colour of the oceans.
- Scientists have worked out that oceans cover about seventy per cent of the surface, far more than land.
- Land covers only about thirty per cent and shows up green and yellow in the photos — clearly smaller.
- Blue oceans cover most of the surface, so the Earth is called the Blue Planet.
- Answer: Because oceans cover about seventy per cent of the surface, more than land; seen from space, the blue oceans stand out most, so the Earth is called the Blue Planet.
6Common mistakes Mistakes
7Quick check Quick check
Q1Which covers more of the Earth's surface?
Q2How much of the surface is land?
Q3What model helps us observe the Earth?
Q4What is the layer of air around the Earth called?
Q5Why is the Earth called the Blue Planet?
8Recap Recap
- The Earth's surface has oceans and land.
- Oceans cover about seventy per cent — more than land.
- A globe is a model that helps us see oceans and land.
- The atmosphere wraps the Earth and protects living things.
- With oceans covering most of it, the Earth is the Blue Planet.