Earthquake
– An earthquake is shaking caused by sudden movements of
rocks in the Earth's crust. They can be extremely violent.
Earthquakes are usually quite brief, but may repeat. Shaking and
ground rupture are the main effects created by earthquakes,
principally resulting in more or less severe damage to buildings and
other rigid structures.
Tsunami
– A tsunami is a series of fast moving waves in the ocean
caused by powerful earthquakes or volcanic eruptions. A tsunami has
a very long wavelength. It can be hundreds of kilo meters long.
Usually, a tsunami starts suddenly. The waves travel at a great
speed across an ocean with little energy loss. They can remove sand
from beaches, destroy trees, toss and drag vehicles, damage houses
and even destroy whole towns.
Volcano
– A volcano is a rupture in the crust of a planetary-mass
object, such as Earth, that allows hot lava, volcanic ash and gases
to escape from a magma chamber below the surface. Earth's volcanoes
occur because its crust is broken into 17 major, rigid tectonic
plates that float on a hotter, softer layer in its mantle.
Therefore, on Earth, volcanoes are generally found where tectonic
plates are diverging or converging.
Tornado
– A tornado is a violently rotating column of air that is
in contact with both the surface of the earth and a cumulonimbus
cloud. They are often referred to as twisters. The most extreme
tornadoes can attain wind speeds of more than 480 km/h. Tornadoes
have been observed on every continent except Antarctica. An EF0
(Enhanced Fujita Scale) tornado will probably damage trees but not
substantial structures, whereas an EF5 tornado can rip buildings off
their foundations leaving them bare and even deform large
skyscrapers.
Forest Fire
– A forest fire is an uncontrolled fire in an area of
combustible vegetation that occurs in the countryside. A forest fire
differs from other fires by its extensive size, the speed at which
it can spread out from its original source, its potential to change
direction unexpectedly and its ability to jump gaps such as roads,
rivers and fire breaks. The four major natural causes of forest fire
ignitions are lightning, volcanic eruption, sparks from rockfalls
and spontaneous combustion. They are caused by humans as well.
Famine
– A famine is a widespread scarcity of food, caused by
several factors including crop failure, population imbalance or
government policies. This phenomenon is usually accompanied or
followed by regional malnutrition, starvation, epidemic and
increased mortality. Some countries, particularly in sub-Sahara
Africa, continue to have extreme cases of famine.
Floods
– A flood is an overflow of water on land which is usually
dry. Sometimes a river receives too much extra water, either from
heavy rain or other natural disasters. When this happens, the water
overflows from its normal path in the river bed and onto dry land.
This is called a flood. Extreme flooding can also be caused by a
tsunami or a large storm that will cause the sea to surge inland.
Floods often cause damage to homes and businesses if they are in the
natural flood plains of rivers.
Hurricane
– A hurricane is a circular air movement over the warm
ocean waters in the warm part of Earth near the equator. Most
hurricanes create strong winds and heavy rains. While some
hurricanes stay out in the sea, others pass over land. This can be
dangerous because they can cause a lot of damage. When hurricanes
reach land, they may break things. Sometimes they kill people and
destroy cities.
Avalanche (Snow Slide)
– An avalanche (also called a snowslide) is a rapid flow of
snow down a sloping surface. Large avalanches may carry stones,
boulders and trees with them. They may bury people under them. If
the people are not found rapidly enough by rescue teams they will
die of suffocation (not getting enough air) or of hypothermia
(freezing cold).
Droughts
– A drought is a period of below-average precipitation in a
given region, resulting in prolonged shortages in its water supply,
whether atmospheric, surface water or ground water. A drought can
last for months or years. It can have a substantial impact on the
ecosystem and agriculture of the affected region.
Lightning
– Lightning is a powerful electrical discharge made during
a thunderstorm. The electric current is very hot and causes the air
around it to expand very quickly, which in turn makes thunder.
Sometimes it happens between clouds. Sometimes (in the rain) it goes
from cloud to ground. If it goes from cloud to ground, it can strike
a person. Around 2000 people are struck by lightning each year.
Cyclone
– A cyclone is a large scale air mass that rotates around a
strong centre of low pressure. They are usually characterised by
inward spiraling winds that rotate counter clockwise in the Northern
Hemisphere and clockwise in the southern. Cyclone is the general
term for a variety of low pressure system types, such as tropical
cyclones, extra tropical cyclones and tornadoes.
Land Slide –
A landslide, also known as a landslip, is a form of mass
wasting that includes a wide range of ground movements, such as
rockfalls, deep failure of slopes and shallow debris flows.
Landslides can occur in underwater, called a submarine landslide.
Landslides occur when the stability of the slope changes from a
stable to an unstable condition. A change in the stability of a
slope can be caused by a number of factors, acting together or
alone.
Meteor (Striking Earth)
– A meteor is what you see when a space rock falls to
Earth. It is often known as a shooting star or falling star and can
be a bright light in the night sky, though most are faint. If it
hits the ground, it is then called a meteorite, and a large one
sometimes leaves a hole in the ground called a crater. Meteors
sometimes hurt people and property. Large meteorite strikes may have
played a part in several of the mass extinctions.
Snow Storm
– Snowstorms are storms where large amounts of snow fall.
Snowfalls in excess of 6 inches (15 cm) are usually universally
disruptive. A massive snowstorm with strong winds and other
conditions meeting certain criteria is known as a blizzard.
Snowstorms are usually considered less dangerous than ice storms.
However, the snow can bring secondary dangers. Snowstorms can
produce cornices and avalanches.
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