Ruth's Natural Disasters Page

Ruth's
Natural Disaster Page

Mountains of Fire
A volcano is a special kind of mountain that actually builds itself. Scientists think that far down in the Earth, where it is fiercely hot, there are pockets of melted rock. It is thought that the pressure of gas pushes this melted rock (called magma) up out of the ground. Once magma comes out of the ground it is known as lava. Lava may be thick like syrup or as thin as watery soup. It cools into a black, gritty rock. It is this rock that builds the volcano. As the lava pours out of the Earth, it piles up into the shape of a cone, with a tunnel running down its middle. The more lava that comes out, the higher and wider the volcano gets.
Volcanos can erupt in different ways. One kind shoots a stream of glowing lava high into the air, like a giant, fiery fountain. Mauna Koa in Hawaii is one of these. Another type of volcano shoots out solid chunks of red-hot rock and cinders. Some volcanos pour rivers of lava through cracks in their sides. And some volcanos blow themselves to pieces. In 1883 a volcano on the Indonesian island of Krakatoa exploded. The tsunami created by the explosion killed more than 36000 people.

Mountains of Fire

A volcano is a special kind of mountain that actually builds itself. Scientists think that far down in the Earth, where it is fiercely hot, there are pockets of melted rock. It is thought that the pressure of gas pushes this melted rock (called magma) up out of the ground. Once magma comes out of the ground it is known as lava. Lava may be thick like syrup or as thin as watery soup. It cools into a black, gritty rock. It is this rock that builds the volcano. As the lava pours out of the Earth, it piles up into the shape of a cone, with a tunnel running down its middle. The more lava that comes out, the higher and wider the volcano gets.

Volcanos can erupt in different ways.

One kind shoots a stream of glowing lava high into the air, like a giant, fiery fountain. Mauna Koa in Hawaii is one of these.

Another type of volcano shoots out solid chunks of red-hot rock and cinders.

Some volcanos pour rivers of lava through cracks in their sides.

And some volcanos blow themselves to pieces. In 1883 a volcano on the Indonesian island of Krakatoa exploded. The tsunami created by the explosion killed more than 36000 people.

When the Earth shudders
"The mountains seems to walk!"
That is what one Chinese writer said about a terrible earthquake that he saw. During a violent earthquake, the ground shivers and shakes and rumbles. Whole sections of land get pushed out of place, so that mountain truely seem to 'walk'.
Earthquakes happen where the plates of the Earth's crust are moving in different directions. The rock in the crust begins to bend because of the pressure, just as a stick will bend if you press on it. Suddenly the rock snaps and breaks, just as the stick would snap if you kept bending it. Like the ripples on a pond, the breaking of the rock sends shivers through the ground, making the ground quiver and quake.
If the earthquake happens under the ocean it causes waves that travel through the water. They move in the same way that ripples travel out from a pebble thrown into a pond. Waves made by earthquakes are called tsunami. Far out at sea, where the water is deep, tsunami may pass under a ship and hardly be noticed. But when the tsunami reach a long shallow shore, they may grow as high as thirty metres as they rush up the beach. This happened in 1755, when a tsunami fifteen metres high wrecked the city of Lisbon on the coast of Portugal.
It also happened in 1998 when a tsunami killed thousands of people at Aitape on the north coast of Papua-New Guinea.

The Eye of the Storm
Tornados are storms that always start over the land. But there is another type of storm which always starts over the warm, tropical oceans.
If this type of storm starts near the West Indies, it is called a hurricane. If it starts over the Pacific Ocean near Asia, it is called a typhoon. If it starts near Australia, it is called a tropical cyclone.
Tropical cyclones are a different shape from tornados. They look like a huge doughnut - a great circle of storm clouds hundreds of kilometres wide. In the middle is a hole where the air is perfectly calm. This hole is called the eye of the cyclone.
No-one knows exactly what causes these storms. They begin over the ocean, near the Equator, where the air is very hot, wet and still. As great masses of this warm, wet air rise up, towering rain clouds form. Sometimes something happens to start the clouds whirling.
A tropical cyclone is a great, whirling circle of wind and rain. The wind of a tropical cyclone is very powerful. It may blow at 330 kilometres an hour. It causes huge ocean waves that rush ahead of the cyclone. If these waves reach land they can cause sudden floods. If a cyclone blows over land the wind can tear up big trees by their roots and push over houses and over buildings.

Floods
When the rain has been pouring down for hours, the water in rivers gradually begins to flow faster as more and more rain water drains into them. The level of the water in the river rises, creeping higher and higher up the river banks. Sometimes, if enough rain has fallen, the rivers are so swollen that they "burst their banks" and begin to flow out over the land on both sides of the river.
When land that is normally dry becomes covered in water, we say that it is flooded. If a river overflows and covers the land where people are living, it can cause a lot of damage. The amount of damage depends on how suddenly the flood happens.
In February 1998, the people in southeast Queensland had some warning that a flood was coming. They put down sand bags to stop the flood water going into their homes but the flood was so high that it ran over the sand bags and into their houses and shops, leaving lots of mud and rubbish for the people to clean up.

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