Natural disasters in the world and their impact on inflicted societies.




A natural disaster is the consequence of a natural hazard which affects human activities, like an earthquake, a tsunami or eruptions. In recent years, the number of natural disasters in Europe has increased. The human and material damages have become more comprehensive. About 3 million people have in the later couple of decades lost their lives caused natural disasters, and over a billion people have got their lives ruined based on these catastrophes.
Developing countries are more exposed than for instance countries like Norway.


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Earthquake



An earthquake is sometimes called a tremor or temblor. It is a result of a sudden release of energy in the Earth’s crust that creates seismic waves. This type of earthquakes is called tectonic earthquakes. Earthquakes caused eruption occurs very infrequently indeed. These natural events can cause massive damage and destruction. To register earthquakes we use seismographs, which measure the intensity after Richter scale. A temblor with magnitude 3 or lower is usually unnoticeable, but with magnitude 7 the tremor will cause serious damage over large areas. The place where an earthquake is released is called hypocentre or focus. The most dangerous earthquakes have its hypocentre quite near the earth’s surface, about 60 km.When an earthquake arises, it disperses a shock wave from the hypocentre. As a consequence of an earthquake we have three different outcomes, a longitudinal wave that makes the particles in stones to vibrate back and forth. We also have transverse waves that make the particles to swing across the wave direction. The last types of wave are long waves that are created when the other waves reach the surface. The long waves give the most intense blow, but the longitudinal waves are the quickest and can be registered first. Over a million people have died and values for several hundred billion dollars have been lost as a result of earthquakes, over the last few centuries. Earthquakes are regarded as the most destructive of all natural disasters. In 1964 an earthquake in Alaska caused the Pacific-mantel to move suddenly under the North American-mantel. These sudden displacements made the earth shake in seven minutes. It opened huge cracks, apartment buildings fell together, and 115 people drowned in the seismic sea wave that arised. Even though the shaking makes houses collapse, the biggest damages is caused by secondary reasons, like fires caused by electric short circuit, spoiled gas main etc.


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Tsunami



The word Tsunami is Japanese and means harbour wave.
A tsunami is a dangerous water level change which occurs suddenly and it is very hard to alert. A Tsunami can occur when there is earthquake, eruption, landslide, explosion or fallout from space.
The greater the depth of the ocean is the faster the wave will move.

How a tsunami is generated:

A tsunami is generated when the earthquakes in the collision zone and the water is pushed up.


26 of December there was an underwater earthquake with a power of 9.0 outside the island Sumatra. The tsunami waves washed the shores in Thailand, Malaysia, India, Sri Lanka, Maldives and Indonesia. 200 000 thousand people died.





Volcano



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image is from naturkatastrofer.no

Volcanoes are Lava Mountains which is a result of motion in the magma of the inner earth. The magma has been squeezed up to the surface through holes in the earth’s crust. Magma is mountain in liquid condition, with a temperature at 1090 and 1200 C°. We estimate that there is about 500 and 600 volcanoes which are in activity. You may recon that a volcano is extinct when there are no longer signs for outburst. Volcanoes with permanent moderate activity characteristics with constant lava flow that make up seas (volcanoes on Hawaii) or they frequently sling out tailings or more and less solidification of lava. The magma in sleeping volcanoes contains very little water and silicon oxide, while lava in the more active volcanoes is rich on silicon oxide and steam. The explosive volcanoes have often a conical form, because thick lava doesn’t run down far before it coagulates. Volcanoes with permanent activity and thinly liquid lava, like the volcanoes on Hawaii, which can send theirs lava flow far away with a speed near to 40 km/h. These kinds of volcanoes are even and often have several outburst gaps.
Volcanoes play an important role when it comes to liberate gas to the atmosphere. Volcano soli is highly fertile. But the volcanoes can do great damage, and outbursts are often disasters. They may cause earthquake and tidal wave.Observational station is built on volcanoes located close to inhabited areas, so that science men should be able to warn about the outburst. The earthquakes can be predict on basis of movement in the magma and changes in the temperature, pressure and the composition of the gas that stream out of holes in the volcano. Satellites are also used to monitor volcanoes, but it is still difficult to predict the outbreaks, and each volcano has its distinctive characteristic and whim.


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image from http://www.jimhollisteragency.com/FloodInsurance.html


Flood


A flood is an overflow or an expanse of water that submerges land, a deluge. This often happens in connection to snow melting and by long-lasting or very strong rainfall. Floods can also occur in rivers, when the strength of the river is so high that the water flows out of the river banks, particularly at bends or meanders and causes damages to homes and businesses along such rivers.
Flood is among the most usual and most expensive natural disasters reckoned in economic losses and human suffering. As much as 90 % of the damages associate with natural disasters, except from drought, is caused by flood. Floods kill nearly twice as much people in USA every year, as the tornado and the hurricanes do together.
Under intense rain it occurs that the rivers flow with huge rate. With its power it can wash away parts of buildings or the pavements in the streets. This type of flood is very usual in cities because with the big areas with asphalt, the water will not be absorbed in the ground. This can result in rivers with powerful stream in the streets and the basements to death traps when they get filled with water.
It is several factorize to why flood take place, but the intensity and duration to the rain is two of the most important.
A flood can create huge damage, either if the water cascade through the landscape and wipes away various objects, or if the water remain on the ground and cause water damages to the buildings. It can also release catastrophic mud-landslides.



SOURCES:

Introduction (Eirin)
Text: http://www.regjeringen.no/nn/dep/ud/Tema/Humanitart-arbeid/Naturkatastrofer.html?id=434482
http://no.wikipedia.org/wiki/Naturkatastrofe


Earthquake (Eirin)
Text: http://www.ngi.no/en/Areas-of-research-and-development/Earthquakes/
http://no.wikipedia.org/wiki/Jordskjelv

Picture: www.fareastgizmos.com

Tsunami (Camilla)
Text: Met.no og wikipedia.com
Picture: http://urbanlegends.about.com/library/bl_tsunami_picture.htm

Vulkano (Camilla)
Wikipedia.com

Flood (Eirin)
Text: http://no.wikipedia.org/wiki/Flom
http://www.atmosphere.mpg.de/enid/1Flom_Tordenv_r/-_Plutselige_flommer_4cf.html