Category Geology

How can you find the parts of the world’s ocean?

The World’s Ocean

Do you think the earth’s surface has more land or more water? Would you believe that most of the planet is covered with water? It’s true. The land we live on, even the giant continents, are really just like big islands in a huge ocean.

Different parts of the ocean have different names, although all these parts combine to form one giant body of water. The two biggest parts are the Pacific and Atlantic oceans. There are also the Indian and Arctic oceans. Some people call the water near the South Pole the Antarctic Ocean. Can you find these parts of the world’s ocean on the globe?

Where did the ocean come from? Many scientists say that billions of years ago the outside of the earth was cool, but the inside was fiercely hot. The heat inside the earth caused chemicals to rise to the surface. Some of these chemicals formed water. Over millions of years, the water filled the low parts of the earth.

Picture Credit : Google

What makes waves?

On a quiet day, you can hear the waves roll in and splash near the shore. On a stormy day, they thunder.

Waves are made by wind blowing along the top of the water. The water seems to be moving forwards – but it only moves up and down. A cork floating on the water would bob up and down as a wave moved under it. This is because the water in a wave does not move forwards. Only the shape of the wave moves forwards.

When a wave reaches land, it “breaks”. The bottom of the wave drags on the ground where the water is shallow. The top keeps going. It spills onto the beach, and then slides back again. This is the only place where the water in a wave moves forwards and back. Everywhere else it just moves up and down.

The biggest waves of all are made by earthquakes under the ocean floor. These waves are called tsunamis. Hundreds of kilometres from shore, a tsunami may only reach 30 or 60 centimetres. People on a ship at sea may not even feel it. But as a tsunami approaches land, it can form a wall of water more than 30 metres high.

Picture Credit : Google

What are glaciers?

All that ice

A glacier is a large mass of ice that flows slowly over land in cold Polar Regions and high mountain valleys. Glaciers begin as snow on a mountaintop. As more snow falls, the weight of the new snow squeezes the snow already there. The snow on the bottom of the pile turns to ice. The ice becomes a glacier.

There are two kinds or glaciers. One is like a river of ice that slides down from the top of a mountain. The other is like frosting on a cake. It may cover entire mountain ranges and even whole continents.

When a glacier reaches the edge of the frozen land, a large crack will appear in it. With a loud noise like thunder, a huge piece of the glacier falls into the sea and floats away. This piece is called an iceberg.

The land called Antarctica, around the South Pole, is covered by a giant glacier. A sheet of ice that is more than 1.6 kilometres thick covers Antarctica. Under much of this ice is land with mountains, valleys, and plains.

Picture Credit : Google

Which are the various parts of the sea?

The Bottom of the Sea

The sea floor has many mountains, plains, deep valleys, and even volcanoes! Its mountain ranges are longer and wider than those on land. Its valleys are longer and deeper, too.

The earth’s surface is covered with a rocky crust. The high parts are the continents and islands, and the low parts are under the sea. The deepest parts are long, narrow valleys called trenches. Earth’s deepest trench is almost 11 kilometres deep in one spot.

Large mountains rise from the sea floor. In some places, they rise high enough to appear above the water. Many of these mountains are volcanoes. Hawaii is made up of volcanic islands.

Great mountain ranges in the oceans are called ridges. Iceland is part of a ridge in the middle of the Atlantic Ocean. Smaller ridges are found in the Pacific Ocean.

Isn’t it surprising that you can find all of these different kinds of land at the bottom of the sea?

Picture Credit : Google

What are Deserts?

The glowing sun glares down on a vast sea of sand. As far as the eye can see, sand stretches in great brown ripples. The air is so hot it seems to shimmer as it rises from the sand. Not even the tiniest green plant is in sight.

Most people picture this endless, hot sandy land when they think of a desert. But there are many kinds of deserts. Some deserts are sandy places with very few plants. Others are flat plains with many kinds of plants. Some deserts are bare spots near seashore, while others are rocky areas high in the mountains. Some deserts are hot all year round. Others are hot or warm only in summer.

But one thing that is true of all deserts is that they are places where little rain falls. It does rain in deserts, but usually not much. Some parts of deserts get just a sprinkle every few years. Sometimes a desert is so hot that the rain dries up before it reaches the ground! In some deserts, heavy rain can cause sudden floods because the earth can’t soak up water fast enough.

Scientists say that some deserts were once green and fertile. Changes in climate made the rains stop and turned the land to desert.

The dry wind whispers as it passes over high, rocky deserts. Here there is little change. The rocks look the same year after year. But in a sandy desert, you might have a hard time finding the same spot from one year to the next. Hills of sand, called dunes, shift and change shape.

There are two kinds of dunes in the desert. One is usually crescent-shaped. A crescent is like a half circle. This dune builds up gradually into a long slope on the side from which the wind comes. It then drops steeply on the other side.

The second type of dune takes shape along the same direction that the wind blows. It has long, wavy ridges with the same kind of slopes on both sides.

Winds shift the sand from one shape to another. As desert sands shift, the dunes move. As the dunes move, they can cause a lot of damage to any buildings in their path. Desert towns sometimes disappear under shifting sand.

Picture Credit : Google

What are Plains?

Have you ever travelled across land where the sky seems bigger than the countryside around you? If so you probably saw a part of the earth called a plain. The land is so flat that you can see great distances all around.

Most plains are lower than the land around them, but they are not deep like a valley. Many people live on plains because the soil is good for farming. Also, building homes and roads is easier on the flat land of plains than it is in mountainous places.

Plains may be found along a coast or inland. Coastal plains are lowlands that stretch along an ocean’s shore. They might be elevated parts of the ocean floor. Or they can be formed by solid materials carried off by water from other coastal plains. Coastal plains usually rise from sea level until they meet higher land, such as mountains.

Inland plains may be found at high levels. The Great Plains, which cover part of the U.S.A. and Canada, slope upwards from about 600 to 1,000 metres above sea level. There they meet the Rocky Mountains.

Thick forests thrive in the damp air along coastal plains. Other plains, like those in which the sky seems so big, have few trees, but they have lots of grasses.

Picture Credit : Google