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Natural Disasters

Tornadoes, Hurricanes, Earthquakes and stuff

sam yu

on 5 December 2012

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Transcript of Natural Disasters

Natural disasters - Natural Disasters -Natural Disasters - Natural Disasters- Natural Disasters - Natural Disasters - Natural Disasters - Natural Disasters - Natural Disasters Lets start with
Tornadoes Tornadoes Are violently rotating counter-clockwise columns of air Are similar to hurricanes but wind-speeds are faster, and the destruction path of tornadoes is more concentrated. Damage done
by a tornado is rated on the
Fugita Scale,
F0 being the least damage
and F5 the most. There is an area in the united
states known as tornado alley
which comprises mainly of Texas, Kansas, Oklahoma
and Nebraska. Tornadoes hit these parts the most The chances of a F5
tornado are incredibly
small, they occur only
about 0.1% of the time. Tornadoes also last for
a much shorter period and the path of a tornado unlike a hurricane is unpredictable. How are they created? Scientists don't have a complete understanding, but they believe they are associated by a super-cells (simply referred as a rotating thunder-storms).
Rarely, the base of the tornado is a cumulus cloud. An interesting fact about tornadoes is that they can transform into similar weather phenomenon Related phenomenon Waterspouts The super-cell tornado hovering above the body of water is less strong then its counterparts. The tornado does not suck up water, but the liquid appearance is caused by condensation. Water spouts are quite rare Dust-Devils Are tornadoes occurring on dry, sandy
land, like this one in Arizona, They are
strong, well built, and long-lived, but they rarely are big enough to pose a threat to
people and property. The wind-speed of a dust-devil
is much slower than a regular tornado Fire-whirl These are tornadoes that spawn most commonly during a wild-fire. Are dangerous, having wind speeds up to 160 miles per hour and lasting up to 20 minutes. They have caused damage and deaths in the past. Sounds scary eh? Steam-devil Usually form over hot geysers and
basins like in Yellow Stone National
Park, but can form in lakes or other
bodies of water as well. They dissipate
quickly if away from its source, and are
fairly harmless. Are rare like water spouts Moving on: Earthquakes Earthquakes Earthquakes Are seismic waves released by tectonic plates
or a collapse within the Crust of the Earth. The power of a earthquake is rated on the
Richer scale, from 1-10 The most powerful earthquake in recorded history of all time struck chile and the power of it was 9.5 The most powerful earthquake
(not in recorded history) that ever
struck Earth happened about 65 million years ago, when a meteorite that wiped out all the dinosaurs landed in the Gulf of Mexico. Creating enormous tidal waves and one EPIC earthquake. Seismic waves
that are released
during a earthquake
are split into 3 groups. P-waves
Surface waves The three
types of waves are; P waves -compresses the crust -travels 6km/second -fastest traveling wave S waves (shear waves) - creates a up and down motion
as it passes through the crust -travels 4 km/second -usually second to arrive Surface waves - travels the slowest - causes the most damage
do to its long duration There are two types of surface waves Rayleigh waves,
Love waves Rayleigh waves The rolling motion created beneath
the crust makes the ground go up
and down. Love waves creates a horizontal side to side
motion. Causes more damage than
Rayleigh waves. Volcano eruptions Volcano Eruptions What is it? It is lava (from the mantle) spewing out of a weak spot, crack or hole in Earth's crust Can be a hill or mountain
formed by lava Depending on the viscosity of the lava,
in the volcano, it can
either flow gently out
of the opening of an
volcano, if it's not viscous. Or explode out
if it is. One of the most famous
volcano eruptions was
Mount Vesuvius in AD 79
in the city Pompeii More famous
eruptions include Mt. St Helens
in 1980 and the eruption of Krakatoa in 1883,
both notable and devastating eruptions. The four
types of volcanoes are; Strato-volcanoes -the dome of the volcano
is made from alternating
layers of ash and igneous
rock -erupt violently and explosively -usually created from the subduction of two
plates(two plates collide and one plate is forced under the other) Shield volcanoes - enormous, wide and gently sloped volcanoes - non-explosive eruptions - made from layers of basalt:
igneous rock formed by thin lava Cindercone Volcanoes - Are the smallest of the volcanoes

-made from layers of ash and rock

- Known to erupt violently and explosively

More cindercone volcanoes then any other type Submarine Volcano -Volcanoes that form on the ocean floor - magma rises out and cools rapidly in ocean water, forms igneous rock - This build-up of igneous rock can form
islands such as Hawaii Can be either active:
can erupt, Dormant: hasn't erupted in a long time or extinct: will never erupt again Now, Hurricanes Back to the start Hurricanes Hurricanes -high speed winds swirling around
a low pressure center. -occur in the Atlantic: hurricanes that occur in the pacific ocean
are called typhoons and cyclones occur in
the Indian Ocean. Hurricanes that are in the Northern Hemisphere spin clock-wise, Southern Hemisphere hurricanes spin counter-clockwise. A hurricane first begins
as a tropical depression Then, as wind speeds increase,
it progresses into a tropical storm After that, the storm can be considered
a hurricane beginning on category one The damage of a hurricane is
rated on the Saffir-Simpson Damage Scale ; Category one Category two Category three Category four and Category five hurricanes are also
given names, such
as Andrew and David The hurricane
damage scale
bases on two
: Wind-speed, and Storm Surge: which are waves of water created by wind Great and notable
hurricanes Hurricane Katrina -caused property damage
of over 80 billion dollars - arguably the most devastating
hurricane that ever hit the U.S - the rescue crew and FEMA failed to
provide support for the citizens of New
Orleans and chaos ensued -Hit New Orleans The 1970 Bhola Cyclone -Killed over 500,000 people -Struck mainly Bangladesh -Most of the deaths were
due to the storm surge that
flooded many low-lying islands -though rated category 3 on
the Saffir-Simpson Scale The 1935 labor day
hurricane - Had the lowest low pressure
center ever in history -weird fact: 200 world war 1 veterans were killed -caused extreme damage in
the Florida Keys More natural disasters tsunamis famines droughts blizzards avalanches mud slides seche floods limnic eruptions dust storms heat waves wild and bush fires cataclysmic meteors epidemics maelstroms
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