.:.Natural Disasters.:.



Natural disasters occur when a natural hazard affects the environment. It can cause human losses, financial and environmental losses.





What are hurricanes?

hurricane.jpgA hurricane is formed when a thunderstorm in the tropical area can grow into a huge, almost massive, hurricane under some certain weather conditions. Several tropic like thunderstorms are able to rotate around a certain area of low air pressure.This is a Tropical depression. If the depression greatly increases so winds reach 39 miles per hour, this is a tropical storm. If wind speeds are increased to more than 74 miles per hour, it's a tropical cyclone,also known as the hurricane. A study found it interesting that out of 608 storms, 50 turned into tropical storms. A storm will increase in strength if there is a supply of warm, moist air to form it. Warm, moisture filled air is found above warm, tropical oceans. Once they are created, hurricanes take the energy from a warm ocean to become increased with strength. While a hurricane stays over warm water it continues to grow in size. A hurricane fades away when it moves from the tropical area. When a hurricane is in high latitudes, where there is cool water, it loses power. When there are no more supplies, moist air by the ocean surface energizes, or feeds, the storm so it shrinks. It weakens by traveling over land too. The spinning of the storm is because of the Coriolis Effect, an item of the Earth's rotation. This causes the air to be drawn into the center of the lowest pressure point to curve. The inside ai r has to go somewhere, so it rises as it circulates. This rising air cools and condenses, creating clouds. Hurricanes don't occur near the equator because there isn't a Coriolis Effect.


How does a tornado from?
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A tornado is a violent and whirling wind that extends from a cumulonimbus cloud. Sometimes known as a twister, a tornado has a width of a few meters but can be anywhere from a meter to a kilometer long when touching ground. It can travel from a human step to a kilo meter in length at a time, causing great damage in the process. Tornadoes form when two masses of humidity and temperature differing in heat meet.


These are some tornadoes found in the Eastern United States.





Tsunami In Malaysia - Funny home videos are a click away
What is a tsunami?

A tsunami is a series of waves caused by movement under the water. The movement is usually caused by underwater earthquakes. Sometimes, tsunamis are mistaken to be tidal waves, but they are not caused by tidal action at all. To generate a tsunami, the earthquake would most likely be underwater. In deep oceans, tsunamis have very little amplitude (wave height). Wavelengths are up to 1,000 kilometers long, with speeds as fast as a jet liner.



How do earthquakes form?

Earthquakes form under Earth's surface, two sides of a fault that constantly
move, related to one another. This is known as fault slip. The moving of the sides is very rough and is joined by a gradual build-up of energy inside the
earthquake-gallery-3.jpgrocks along the fault. Eventually, the strain gets a lot of pressure. The fault then ruptures, releasing all the energy that was built up. This energy is released as vibrations known seismic waves. It's actually seismic waves that cause destructive effects that are combined with the earthquakes. The location on a fault that the pressure first contrasts at is called the hypocentre, and the position above it on the surface of the Earth is called the epicenter. When the seismic waves reach the surfaces of the earth, they give rise to strong ground, called mountains, causing buildings and other hand-made structures to shake or collapse completely. Earthquakes cause landslides, volcanic eruptions, and even new land mass formations.




How do forest fires occur?

Forest fires are started by either human causes or nature causes. Natural causes
forest_fire.jpgare usually started by a zap of light

ning, a spontaneous combustion, or a dry fuel such as sawdust or leaves. Other cases are by human causes, such as smoking, recreational, or equipment.
There are three elements needed for a forest to
burn: heat, oxygen, and fuel. Without these elements, the fire goes out.
Occasionally the fire will reach out to a more abundant area of trees. Once the fire enters the combustion stage, it can be three main types of fires: smoldering, flaming combustion, and glowing combustion. A smoldering fire is one that emits smoke but has no flames and isn't self-sustained. A flaming combustion is a fire that has present flames. A glowing combustion is a later stage of a fire and is classified by a slower rate of combustion and blue flame.




Avalanche.jpg
How do avalanches occur?

Snow builds up to the point where it cannot support its weight. It then falls
down the mountain. An avalanche usually occurs when a person or thing lands on the weakest point of the mountain.
Most avalanches begin when heavy snow covers a less dense layer. The bottom
layer of colder snow with more air pockets is the reason for the dense difference, while the top layer is getting warmer and melting. When snow blows, it can form areas of snow hanging over the edge of a mountain. When something heavy moves the snow, the weak layer gives out, and top layer falls.




How do volcanoes form and erupt?

Volcanoes form usually when two tectonic plates push against each other, causingvalcono.jpg friction in the surface. The plates then push the ground up, forming a volcano.
Volcanoes erupt when the build-up of magma and ash suddenly becomes too unbearable and the volcano spews, creating a stream of extremely hot lava running down the volcano sides and exploding from the top. After an explosion,
the volcano then waits for the lava to dry, creating more mountainous area for the volcano. Never get near a volcano after it erupts...the lava's temperature gets up to a range of 1300-2400 degrees Fahrenheit!




flood.jpg
How are floods caused?

Floods are usually caused by a huge down pour. If there is a thunderstorm, then that also causes a flood, along with tornadoes. Floods are common around places that are moist and lush. They occur when a huge amount of rain pours down for a long period of time. The ground and drains get so full that they overflow and water spews into the streets and other areas.



drought.jpg
How do droughts occur?

Droughts are changes in the weather where there is very little rain or snow for a long period of time and there is also very little food. A drought is when an area has less than 0.25 millimeters of rain, storms, etc. for over 15 days. Droughts aren't normally known as disasters. They are just normal areas where extremely hot, sunny weather occurs. They are only classified as disasters when they last for long periods of time, and when a numerous amount of people are effected.




Information brought to you by: Google.com/search
www.windows2universe.org/earth/tsunami1.html
eo.ucar.edu/webweather/hurricane2.html
www.earthquakes.bz/howdoearthquakesform.html
www.nhm.ac.uk › Nature online › Earth › Natural disasters
www.naturaldisasters.ednet.ns.ca/Projects/Avalanche/bja.htm
www.familyonbikes.org/educate/lessons/volcanoes.htm
library.thinkquest.org/C003603/english/.../causesoffloods.shtml
answers.yahoo.com › Science & Mathematics › Weather
library.thinkquest.org/10136/tornado/torntq.htm