8th Class

Some Natural Phenomena

Synopsis

• High speed winds are accompanied by reduced air pressure.

• Air moves from a region of high pressure to low pressure.

• A thunderstorm occurs due to strong, upward rising winds along with swift movement of the falling water droplets carried with lightning and sound.

• A thunderstorm may develop into a cyclone or a hurricane with wind speed being as high as \[\text{200}\,\text{km}\,{{\text{h}}^{-1}}.\]

• A tornado is a dark, funnel shaped cloud that reaches the ground from the sky. A tornado may form within cyclones and can reach a speed up to \[\text{300}\,\text{km}\,{{\text{h}}^{-1}}.\]

• Electroscope is an instrument used to detect the presence of electric charge on a body.

• An electrical charge can be transferred from a charged object to another through a metal conductor.

• The process of transferring charge from a charged body to the earth is called earthing.

• Lightning takes place when large amount of accumulated charges in the clouds passes onto the earth through atmosphere.

• Lightning conductors are used to protect tall buildings from the effect of lightning.

• An earthquake takes place due to disturbance inside the earth's crust.

• The weak zones on the earth's crust, prone to earthquakes, are known as seismic or fault zones.

• The power of an earthquake is expressed in terms of its magnitude on a scale called the Richter scale. Higher the magnitude, greater is the damage.

• Seismographs are instruments which record tremors produced by the earth.

• Lightning, cyclones and earthquakes can cause extensive damage to mankind and properties. We should take necessary steps to protect ourselves during such natural calamities.