Classification of natural disasters

A natural hazard is an extreme natural phenomenon that threatens human lives, activities, the environment of life, and property. Natural disasters are the destructive events caused by natural factors. They lead to heavy financial, environmental or human losses. The resulting loss depends on the ability of the affected population to resist the hazard. Due to considerably higher hit rate and global warming natural disasters often occur in the world. There are more than 700 of them each year.

Natural disasters are classified according to their cause and their speed of onset. According to their cause natural disasters are divided into geological, climotological and environmental natural disasters. The examples of geological natural disasters are earthquakes, landslides, volcanic eruptions, avalanches, etc. Floods, tsunamis, hurricanes, tornadoes, storms are considered climotological natural disasters. Environmental natural disasters include droughts, famine, pest infestation, desertification, deforestation.

According to their speed of onset natural disasters are classified into sudden and slow natural disasters. Earthquakes, floods, volcanic eruptions, avalanches are natural disasters, which occur suddenly. Slow natural disasters are usually the result of adverse weather conditions combined with poor land use. They include droughts, famine, environmental degradation, etc.

Natural disasters have a great impact on a society. Thousands of people are affected by natural disasters every year. The biggest visible consequence of natural disasters is the physical damage. Homes, buildings, facilities, installations as well as vehicles are destroyed within a short period of time. That’s why international law requires that states should take all necessary measures to ensure the protection and safety of persons.

Questions on Text A

1. What is a natural disaster?

2. What does the resulting loss in the event of a natural disaster depend on?

3. How are natural disasters classified?

4. What is the classification of natural disasters according to their cause?

5. Could you name any geological natural disasters?

6. How are natural disasters classified according to their speed of onset?

7. Could you name any sudden natural disasters?

8. Which slow natural disasters do you know?

9. What are the consequences of natural disasters?

10. What are the reasons of natural disasters’ increase?

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Text B

Tornadoes

A tornado is one of the most destructive natural disasters. The most extreme tornadoes can reach wind speeds of more than 300 mph, stretch more than two miles across, and stay on the ground for dozens of miles.

The main characteristics of a tornado are shape, size, colour and rotation. A typical form of a tornado is a funnel. However, tornadoes can appear in many shapes and sizes. Small, relatively weak landspouts can be visible as a small swirl of dust on the ground. Large single-vortex twisters, often violent, are known as wedge tornadoes or wedges. Tornadoes in the dissipating stage can appear like narrow tubes, or ropes and are called rope tornadoes.

Tornadoes, depending on the environment in which they form, can have a wide range of colors. For example, tornadoes forming in a dry environment can be nearly invisible, marked only by swirling debris at the base of the funnel. Funnels which pick up little or no debris can be grey to white.

Another characteristic of a tornado is rotation. Tornadoes normally rotate cyclonically. Approximately 1% of tornadoes rotate in an anticyclonic direction in the northern hemisphere.

There are at least two scales for rating the strength of tornadoes. They are the Enhanced Fujita and TORRO scale. The Enhanced Fujita scale (EF) rates tornadoes by caused damage from 0 to 5. For example, an EF0 tornado is the weakest one. It damages trees, plants, crops but not substantial structures. An EF5 tornado is of the strongest category. It rips buildings off their foundations and can deform large skyscrapers. The TORRO scale (T) ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.

The United States experiences by far the most tornadoes of any country, and has also suffered the most intense ones. The time of year is a big factor of the intensity and frequency of tornadoes in the United States. On average, in the United States as a whole, the month with the most tornadoes is May, although tornadoes can occur at any time of year. They tend to occur in the afternoons and evenings. Over 80% of all tornadoes strike between noon and midnight. They can happen in groups and destroy the whole city.

Date: 2016-04-22; view: 1749