What are tornadoes?

Tornadoes are violent destructive whirlwinds whose force is concentrated into a much smaller area than that of a hurricane. They are very common in the central United States, where...

Which world cities are at risk from flooding?

Many of the world's cities are low lying and threatened by flooding. Bangkok, in Thailand, and Venice, in Italy, are typical old cities built by water because they relied on shipping....

What causes floods?

Flooding occurs when water cannot drain away fast enough in the rivers. In areas of non-porous rock, water runs off the land very quickly and streams and rivers soon overflow. Flooding...

How can people live in extreme climates?

Over millions of years, the human body has altered to suit the climate of the regions we inhabit. In general the hotter the region, the darker the skin of its inhabitants. Also...

Can sand dunes move?

Sand dunes can move slowly, causing deserts to spread over more fertile land. Continuous winds blow the sand to form crescent-shaped dunes. Sand from the top of the dune is blown farther...

Range of climates in the World

Mountains such as the Rockies in North America have a typical alpine climate, because of their height. They are very cold in winter, and the summers are brief. Alpine meadows are...

The desert process

Deserts were once green and fertile areas, until a climate change altered them permanently. Just a small reduction in rainfall causes plants to die off. Without plant roots to bind...

How can forecasters predict the weather?

Meteorologists use a wide range of instruments and techniques to help them track changes in the weather and to predict future weather conditions. Weather forecasters have used simple...

Thunderbolts

A lightning strike discharges about 100 million volts of electricity, and heats the air in its path to more than 33,000°C.The lightning strike travels at 299,792 km per second, which...

How are hailstones formed?

Hail is produced when particles of ice bounce up and down inside a cloud. In cold temperatures, water droplets inside a cloud will freeze into small pellets of ice. As these begin to...

Why do geysers spout hot water?

When water seeps through the ground and reaches magma, hot rock or volcanic gases, it boils violently. This produces steam that can shoot the water out of cracks, causing a geyser....

What is the Ring of Fire?

AII around the rim of the Pacific Ocean is a circle of places of volcanic activity known as the Ring of Fire. The Ring of Fire is caused by shifts in the giant plates that make up the...

How fast do volcanoes grow?

Unlike most geological happenings, the growth of a volcano can be very rapid. In 1943, a farmer in Mexico noticed smoke coming from a crack in the ground in his cornfield. Lava began...

What is a volcano?

Volcanoes are openings in the Earth's crust through which molten lava, red-hot rocks, steam and fumes pour out. We usually think of a volcano as a smoking mountain that erupts explosively...

What is a rockslide?

Rock is broken away from the mountainside by the effects of freezing. Rainwater enters cracks in the rock and as it freezes, it expands and opens the crack wider. As the thaw begins...

Why do clouds form near mountains?

Clouds form when damp air is forced upwards to pass over a mountain range. Air is forced up the face of the mountain because it is unable to go around it. There is usually a high wind...

Are climbers able to breathe at high altitudes?

The higher you climb, the thinner the air becomes, until there is not enough oxygen to support life. On the highest mountains, there is just about enough oxygen for life to survive...

Which are the highest mountains in the world?

The world's highest mountains are in the Himalaya-Karakoram range to the north of India. The Andes Mountains in South America cover a larger area but are not so high. The Himalayas...

On top of the world

After many years Mount Everest was finally conquered on May 29, 1953, when a Nepalese guide. Tenzing Norgay, and a New Zealander, Edmund Hillary, reached the highest point on the...

How are mountains formed?

There are three main ways in which mountains can be formed. Volcanoes form mountains when lava from deep inside the Earth cools and hardens on the surface. Other mountains are formed...

How are limestone caves formed?

Water can actually dissolve certain types of rock, eventually forming underground streams and caves. Carbon dioxide in the air dissolves in rainwater to form a very weak acid, which...

What is a delta?

As a river reaches the sea its flow becomes slower, forming an area known as a delta. As the water slows the tiny particles of silt carried by the current settle to the bottom, forming...

How does a river begin?

Most of the rainwater that falls on the land returns to the sea by way of rivers. Rainwater first soaks into the ground, but once the ground is saturated the excess water begins to...

Whirling to destruction

For centuries sailors have been in terror of being sucked into a whirlpool that would swallow them and their ships. Whirlpools happen when opposing currents meet, causing the water...