Natural Hazards and Disasters
Natural Hazards and Disasters

Natural Hazards and Disasters

1.Earthquake.

.Definition.

“The sudden shaking or rolling of the earth of the earth s surface is called an earthquake”.

Actually earthquake occur daily around the world, but most of them are too mild to be noticeable.

Causes of Earthquake.

.Elastic Rebound Theory.

In 1906,Henry fielding Reid professor of Geology at John’s Hopkins university, presidented “elastic rebound theory”.

If a stretched rubber band is broken or cut, elastic energy stored in the rubber band during the stretching will suddenly be released. Similarly, the crust of the earth can gradually store elastic stress that is released suddenly during an earthquake.

This gradual accumulation and release of stress and strain is now referred to as the “elastic rebound theory”. Of earthquake. Most earthquake are the result of the sudden elastic rebound of previously stored energy.

2.volcanic Eruptions.

Definition.

” The sudden occurrence of a violent discharge of steam, gases and rock fragments at Earth surface”. Some important concepts associated with the description of volcano include.

A. Causes of volcanic Eruptions.

. Sea floor spreading.

Sea floor is broken when plates separated and basalt erupts out of fissure. Fissure extends down to asthenosphere. The Basalt magma rises in the gap to from ocean ridges and volcanoes.

3. Floods.

It is a natural event or occurrence where a piece of land that is usually dry land, suddenly gets submerged under water. Some floods can occur suddenly and recede quickly. Others take days or even months to build and discharge.

Floods occur at irregular intervals and vary in size, duration and the affected area. It is important to note that water naturally flows from high areas to low lying areas.

This means low lying areas may flood quickly before it begins to get to higher ground.

Types of Floods.

There are three major types of floods discussed as.

1.flash floods.

Flash flood is a rapid flood. It can occur in hours even in minutes. It is most destructive as it has no warning system and get the people by surprise. It usually occurs with heavy rainfall with slow moving thunderstorm.

2.Rapid on set floods.

It is usually take longer time than flash flood and the flood can last for a day or two. This is also destructive but lesser than flash flood as people get time to escape.

3.slow on set floods.

This kind is usually as a result of waterbodies over flooding their banks. They tend to develop slowly and can last for days and weeks.

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