My Science School

Deserts are the driest places on Earth. In some deserts it doesn’t rain for years at a time. In others, it never rains at all. Some deserts are also scorching hot. In the daytime, the sand’s hot enough to fry an egg on.

Can sand dunes move?

Strong winds blowing across the desert pile the sand up into giant heaps, or dunes. The biggest stand 200 metres tall. The dunes creep forward every year and can bury whole desert villages.

Amazing! The Sahara Desert is the biggest, sandiest desert in the world. It covers about a third of Africa.

Are all deserts sandy?

No, they’re not. Only about a quarter of all deserts are sandy. Most deserts are rocky or covered in gravel and stones. Some deserts have high mountains or strange-shaped rocks towering up from the ground.

Is it true? Mushrooms grow in the desert.

Yes. Well mushroom-shaped rocks. They’re carved into shape by sand blown by the wind, like a giant piece of sandpaper.

Picture Credit : Google

The biggest freshwater lake on Earth is Lake Superior in North America. It covers 82,350 square kilometres. That’s almost as big as Austria. Lake Superior is one of five huge lakes called the Great Lakes.

Amazing! The Dead Sea in the Middle East is so salty; you can float on the surface. No fish can live in it.

Is it true? There’s a monster in Loch Ness.

Maybe. Some people say Nessie is a type of prehistoric reptile that lives in the lake. Others say this is nonsense. What do you think?

Where is the highest lake?

Lake Titicaca in South America is the highest lake on which boats can sail. It’s 3,810 metres up in the Andes Mountains. People who live around the lake build boats from lake reeds.

How are lakes made?

Some lakes formed long ago, in hollows scraped out by ice. These filled with water as the ice melted. Some lakes form in the tops of volcanoes or when a river cuts through a bend.

Picture Credit : Google

Rivers begin as fast-flowing streams high up on mountainsides. Some streams bubble up from underground. Others flow from lakes or trickle from the tips of icy glaciers when they start to melt. The start of a river is called its source.

Amazing! The world’s shortest river is D River in Oregon, USA. It’s a titchy 37 metres long. Is the Nile or the Amazon the longest river?

The Nile in Egypt is the longest river on Earth. It flows for 6,695 kilometres. The Amazon in South America is just 295 kilometres shorter.

How high are waterfalls?

The highest waterfall in the world is Angel Falls in Venezuela. It plunges 979 metres down the side of a mountain. Angel Falls are 20 times higher than the famous Niagara Falls in North America.

Is it true? Rivers flow into the sea.

Yes. Most rivers flow into the sea at their deltas. But some rivers flow into lakes and a few flow into deserts.

Picture Credit : Google

Twice a day, the sea washes on to the shore at high tide. Then it flows back out again at low tide. The tides are caused by the Moon and Sun pulling the sea into giant bulges on either side of the Earth.

Amazing! If all the coasts were straightened out, they’d stretch round the Earth 13 times. At 90,000 kilometres, Canada has the longest coast.

Why are beaches sandy?

Sand is made from tiny fragments of rock and shells, crushed up by the wind and water. Sand is usually yellow or white. But some sand is black because it contains volcanic rock or coal.

How are cliffs carved out?

Along the coast, the rocks are worn away by the force of the waves. As the waves crash against the shore, they carve out cliffs, caves and high arches. Sometimes an arch collapses, leaving a stack, or pillar, of rock.

Is it true? White horses swim in the sea.

Yes. But they’re not real horses. They’re the white, foamy tops of the waves as they gallop towards the shore.

Picture Credit : Google

The sea is absolutely huge! Salty sea water covers about two-thirds of our planet so there’s far more sea than land. The sea lies in five oceans — the Pacific, Atlantic, Indian, Arctic and Southern Oceans.

Amazing! The first person to set sail around the world was Ferdinand Magellan. He set off from Spain in 1519. Magellan died but one of his ships made it back three years later.

Which is the biggest ocean?

By far the biggest ocean is the vast Pacific. It alone covers a third of the Earth. At its widest point, between Panama and Malaysia, it stretches almost halfway around the world.

Is it true? The Arctic is the warmest ocean.

No. The Arctic’s the coldest ocean of all. For most of the year, it’s covered in ice.

Why is the sea salty?

The sea’s salty taste comes from ordinary salt. It’s the same stuff you sprinkle on your food. The rain washes the salt out of rocks on land, and then rivers carry it into the sea. The people in the picture are collecting salt left after sea water dries.

Picture Credit : Google

Icebergs are giant chunks of ice that break off the ends of glaciers and drift out to sea. Only about a tenth of an iceberg shows above water. The rest is hidden under the sea. This makes them very dangerous to passing ships and boats.

Amazing! In 1912 the luxury liner, Titanic, hit an Iceberg and sank in the North Atlantic. It was on its maiden (first) voyage from Southampton to New York.

Which was the biggest iceberg?

The biggest iceberg ever was seen near Antarctica. It was about the size of Belgium! The tallest iceberg was more than half as high as the Eiffel Tower in Paris.

Which is the longest glacier?

Glaciers are enormous rivers of ice that flow slowly down a mountainside. The Lambert-Fisher Glacier in Antarctica is over 600 kilometres long. It’s the longest glacier in the world. About a tenth of the Earth is covered in icy glaciers.

Is it true? Baby icebergs are called calves.

Yes. When a baby iceberg breaks off a glacier, it is called ‘calving’. Even smaller icebergs are called ‘bergy bits’.

Picture Credit : Google