Wednesday, April 15, 2009


Lightning is an atmospheric discharge of electricity usually accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms.[1] In the atmospheric electrical discharge, a leader of a bolt of lightning can travel at speeds of 60,000 m/s (220,000 km/h), and can reach temperatures approaching 30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known as fulgurites which are normally hollow and can extend some distance into the ground.[2][3] There are some 16 million lightning storms in the world every year.[4]
Lightning can also occur within the ash clouds from volcanic eruptions, or can be caused by violent forest fires which generate sufficient dust to create a static charge.[1][5]
How lightning initially forms is still a matter of debate:[6] Scientists have studied root causes ranging from atmospheric perturbations (wind, humidity, friction, and atmospheric pressure) to the impact of solar wind and accumulation of charged solar particles.[4] Ice inside a cloud is thought to be a key element in lightning development, and may cause a forcible separation of positive and negative charges within the cloud, thus assisting in the formation of lightning.[4]

Saturday, January 31, 2009


A tornado is a violent rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of up to 300 mph. They can destroy large buildings, uproot trees and hurl vehicles hundreds of yards. They can also drive straw into trees. Damage paths can be in excess of one mile wide to 50 miles long. In an average year, 1000 tornadoes are reported nationwide.

Thursday, January 29, 2009


Flooding is a coast to coast threat to the United States and its territories in all months of the year. National Flood Safety Awareness Week is intended to highlight some of the many ways floods can occur, the hazards associated with floods, and what you can do to save life and property.Flooding can be caused by a range of situations that include:
Seawater flooding – coastal areas may be flooded when a cyclone or severe storm causes a surge of sea water.
Tidal flooding – floods that are caused by high tides that coincide with higher than normal river levels.
Run-off from rivers and dams – flooding can be caused when river systems all need to carry more water at the one time following a snow-melt or when dams start to overflow.
Urban drainage – flash flooding is a serious problem in some cities when the drainage systems fail. People can be caught in stormwater drains, trapped in their cars or even swept off the roads by water.

Wednesday, January 28, 2009


Violent wind storms are called cyclones in Australia, and are known as typhoons and hurricanes in other countries.Tropical cyclones begin over warm tropical seas in areas of low atmospheric pressure. The warm, moist air begins to spiral and becomes a strong, circling, wind storm. In the centre of a cyclone, there is a calm area called the 'eye'. In the eye, the sky is clear and there is only a light wind blowing.
Cyclones can change direction suddenly, which makes it very difficult for meteorologists to forecast what will happen. Tropical cyclones bring heavy rain and cause high waves.
Cyclones cause damage
Cyclones move at up to 360 kilometres per hour, bringing heavy rain. The wind and rain causes lots of damage when the cyclone crosses over coastal lands.

Stormy skies

A storm is a time of bad weather , often with black clouds, heavy rain or hail, thunder and lightning , and very strong wind. In cooler areas of the world, storms usally happen along weather fronts. In hotter areas , storms develop because hot air rises and cools to make clouds and rain. The worst storms are hurricanes, which develop over land.


A volcano is a hole in the earth's crust through which hot, liquid rock pours out from inside the planet. As the rock cools down, it makes hills and mountains. Most volcanoes are found on the edges of the earth's plates. From time to time an active volcano erupts, or explodes. A volcano that has not erupted for many years is said to be extinct.
Mountain of lava
Below a volcano is a chamber, or pool, of red hot, liquid rock called magma. As pressure increases in the chamber, the magma is forced up to the surface through a central vent, or pipe. it erupts from the crater. On the surface, magma is called lava.

Tuesday, January 27, 2009


An earthquake is a sudden shaking of the earth's crust. Most earthquakes happen when the edges of plates slide past each other. The rocks jerk suddenly or shudder, making the surface of the earth shake. There are about half a million earthquakes each year, but only about a thousand because any serious damage. When earthquakes happen under the sea, they sometimes make enormous waves, called tsunami.

During an earthquake
The shock waves from an earthquake spread out from a point called the focus. The worst damage happens at a point on the earth's surface called the epicenter. It lies above the focus, often on a fault line.