Know More..

Category Geology

Why do Mountains explode?

A volcano is a special kind of mountain that actually builds itself! It is made of red-hot rock that pushed up out of a crack in the earth.

A volcano begins deep inside the earth when the force of hot gas pushes melted rock up. With a loud, deep rumble, the ground begins to shake and burst open. Fiery hot rock can shoot into the air, and melted rock may flow out of the earth. With the volcano, there may be earthquakes and explosions. Huge clouds of smoke and ash may fill the air.

The melted rock is called magma. Magma that pours out onto the earth’s surface is called lava. Some lava is as thick as syrup, and some is as thin as soup.

As thin lava stops flowing and cools, it hardens into smooth sheets of rock. Thicker lava cools into rough, jagged sheets.

As more lava pours out of the earth, it falls on the cooled rock. As the ash and rock pile up, a new mountain forms. It forms a cone-shaped mountain with a deep tunnel down its middle.

Picture Credit : Google

Why mountains are there?

Some mountains are no more than steep hills covered with grass and trees. Others rise high into the atmosphere with snow-covered peaks. Often mountains stretch out in long chains called mountain ranges.

Mountains are formed over long periods by tremendous forces in the earth. These forces move parts of the earth’s crust in different ways, making different kinds of mountains.

Mountain ranges are important because they influence the climate and water flow of the land around them. How do they do this? Air cools as it reaches high altitudes. And cold air holds less water than warm air does. So as the warm air turns cooler near the tops of the mountains, it releases water in the form of rain or snow. This rain or snow feeds nearby rivers and streams. Mountains are also important as homes for plants and animals and as a source for minerals.

Scientists say the earth’s mountains are millions of years old. The youngest mountains have rugged, sharp peaks. Older mountains are smoother, with rounded tops. These older mountains have been worn down by wind and rain over millions of years.

But all mountains begin to wear away, or erode, even while they are rising. Rainfall washes away tiny pieces of rock. The wind carries away dust and earth.

Water seeps into cracks in the rock and freezes. Ice takes up more space than water, so it forces the cracks open. This happens over and over until rocks break off and fall down the mountainside. After millions and millions of years, all of these forces wear away the mountains.

There are five different kinds of mountains.

Fold Mountains form when sections of the earth’s crust meet head-on. This makes layers of rock in the crust crumple and fold. They often make wave-like patterns.

Fault-block Mountains form when earthquakes make the earth’s crust break into large blocks that are tilted or pushed out of place.

Dome Mountains form when forces inside the earth push the earth’s crust up into a huge bulge or dome.

Erosion Mountains form when rivers or glaciers flow over a high, flat area of rock. They wear it away to form peaks and valleys.

Volcanic Mountains form when molten rock from deep within the earth erupts. It pushes up through the earth and piles up on the surface.

Picture Credit : Google

Describe the plates of Earth?

The Earth’s Plates

It may seem that the earth’s crust is one gigantic piece of rock. But the outer shell of the earth is divided into about 30 large and small pieces that fit together like a puzzle. These pieces are called tectonic plates.

The plates move on a very hot layer of rock within the mantle. The plates move very slowly, only from 1.3 to 20 centimetres per year.

The continents sit on top of the plates. When the plates move, they take the continents with them. But the plates aren’t only under the continents. They are also under the ocean floor. They are under water on the continents, such as lakes and rivers, too.

Under land, the plates are about 100 kilometres thick in most places. In some places in the world’s oceans, they may be less than 8 kilometres thick.

As the plates move, the continents and oceans slowly change. Scientists think that in 50 million years, South America and Africa will be further apart. They think the Atlantic Ocean will be wider, and the Pacific Ocean will be smaller.

Picture Credit : Google

Who Studies the Earth?

Some of the world’s best detectives are the people who study the earth. They are called geologists.

Geologists help us learn about the earth’s resources and how to care for them. They tell us how to preserve these resources and to use them properly when we must. Some geologists study where to build homes, bridges, and dams safely. These scientists also work to protect people from earthquakes, floods, and other natural disasters.

Geologists may be found chipping rocks on a mountainside or drilling on the ocean floor. Sometimes geologists work indoors. They X-ray rock samples, do research and tests on computers, or make maps of places they want to explore.

Geologists may travel all over the world. They search mountains, swamps, deserts, and the bottom of the ocean, so that we can learn more about the earth. They may tramp through rain forests, go underground into mines, or climb around an icy glacier.

Geologists and many other kinds of scientists uncover the secrets of the earth in different ways. Sometimes such scientists are called earth scientists.

Environmental geologists work to solve problems of pollution. They search for the best ways to get rid of hazardous waste – materials that are dangerous to our health.

Meteorologists study the weather and the air that surrounds the earth. They predict weather conditions.

Mining geologists study the earth’s rocks and ways to remove them.

Mineralogists identify and study the 3, 000 or so kinds of minerals found on the earth.

Petroleum geologists search for oil and natural gas on land and beneath the ocean floor.

Seismologists study the motion of the earth. They watch for earthquakes. Most earthquakes occur underwater.

Geochemists study the chemicals in the earth’s crust, its waters, and its atmosphere and why they are there.

Palaeontologists study fossils of animals and plants to learn about the earth’s past.

There are many kinds of earth scientists, but they have one thing in common. They all enjoy studying the earth and want to uncover its secrets.

Picture Credit : Google

What is Oil?

Maybe you have used oil on your bicycle chain to keep it from squeaking. Did you know that oil was once part of the earth? It starts as a thick dark liquid called crude oil that is found between layers of rock deep inside the earth’s crust. Crude oil is also called petroleum.

Crude oil is a fossil fuel. This means that it started forming millions of years ago from dead plants and animals that had lived in the ocean. Over millions of years, these dead plants and animals piled up on the ocean floor. Thick layers of sand and soil covered them. The sand and soil squeezed together under their own weight and the weight of the water pressing down on them. They were pressed so hard that they turned into rock. Scientists believe that the weight of the rock helped turn the piles of dead plants and animals into oil.

People today use oil for many things. They use oil to heat homes and to run cars, planes, trains, ships, and trucks. They also use oil to make such things as medicines and plastics.

Oil companies get oil by drilling into the earth’s crust. They pump out the oil that is trapped under the earth’s surface. They even pump oil from under the ocean floor.

Because of its many uses, oil has become very valuable. But it takes millions of years for the earth to make more oil, so we need to make sure we don’t waste it.

Picture Credit : Google

What are Fossils?

Imagine a giant dinosaur moving along a lakeshore 80 million years ago. It is searching for food. The dinosaur sees some plants and wades out to them. But before it reaches the plants, it steps into a deep hole filled with soft, wet mud. The dinosaur sinks deeper and deeper into the mud, and the dinosaur drowns.

Over time, the soft parts of the animal’s body rot away. Only its bones are left, covered by mud. For many years, layers of sediment pile on top of the mud and pack it tightly around the bones. Eventually, the packed mud turns to clay. After many more years pass, the clay turns to rock.

During all this time, minerals in the water of the lake fill the hollow places in the bones. The minerals harden and the skeleton of the dinosaur is preserved. The bones in the rock are called fossils.

There are other ways for fossils to be made. And, fossils exist for many kinds of living things – from bugs to plants to woolly mammoths – not just for dinosaurs.

Picture Credit : Google

Why are deserts dry?

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

Which lake is the biggest?

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

Where do rivers begin?

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

Why does the sea flow in and out?

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