Transcript NATURAL DISASTERS NA1A

INDEX FOR YOU TO
KNOW 
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1 : INTRODUCTION
2 : FLOODS & DROUGHTS
3 : EARTHQUAKES
4 : HURRICANES
5 : GENERAL CONCLUSION
6 : THE END
INTRODUCTION
• We have always known about the high destructive
power that our planet has.
• Earhquakes, tsunamis, floods, droughts, hurricanes
have caused hundreds of thousands of deaths as
well as damage valuated in billions of dollars in the
last century. Many of them seem to have increased
in frequency and intensity.
• Is this a natural fact or, do human beings have
something to do with?
FLOODS
Floods
temporary covering of water
of land that is not normally covered by
water.
heavy rainfalls
Caused snow melt
by
hurricanes
tsunamis
Prevent
move away from rivers
WAYS OF PREVENTING FLOODS
FRANCE:
RESERVOIRS TO REMOVE
PRESSURE FROM THE SEINE
GREAT FLOOD, PARIS
1910
• LONDON:
protected from sea flooding by mechanical barries
• VENICE:
EXAMPLE
• FLOODING OF BIESCAS:
 7th of August of 1996
• JAPAN
– 11th of March 2010
DROUGHTS
• Droughts
extended period of months
or years when a region notes a deficiency in its
water supply.
reduction in water quality
consequences
famine
malnutrition &
dehydratation
migration
wars
wildfires
EARTHQUAKES AND TSUNAMIS
What is an Earthquake?
• Ground movement caused by the sudden
release of seismic energy due to tectonic forces.
The focus of an
earthquake is the
location of the energy
released inside the
Earth’s crust.
The epicentre is the point
on the Earth’s surface
directly above the focus.
Where that it takes place ?
• This commonly occurs due to
movement along tectonic plate
boundaries.
Magnitud
e
Earthquake Effects
Approx.
number each
year
< 2.5
2.5-5.4
Usually not felt, but recorded
900,000
30,000
Often felt, only minor damage
5.5-6.0
Slight damage to buildings and
other structures
500
6.1-6.9
May cause a lot of damage in very
populated areas
100
7.0-7.9
Major earthquake. Serious
damage.
20
> 8.0
Great earthquake. Can be totally
destructive near the epicentre.
1 every 5-10
years
• Magnitude 7.7 - 8.3
How do we mitigate the
hazard from earthquakes?
• Reinforcing buildings
• Education
• Disaster plans
Earthquakes and Tsunami’s
• An earthquake under the ocean has the
potential to form a tsunami.
• The earthquake must vertically displace
overlying water (extensional or
compressional faults - not transform)
Extension
Compression
Transform
2004 South Asian
Boxing Day event
• Biggest
earthquake in 40
years!
• Magnitude 9.2
• 150 km off the
west of Northern
Sumatra
• Generated a
disastrous tsunami
in 12 countries
Tsunami
Above: Countries most effected by
the tsunami
Animations of
the Boxing
Day tsunami
showing how
the tsunami
radiated from
the entire
length of the
1,600 km (994
miles) rupture.
A village
near the
coast of
Sumatra
lays in ruin
after the
tsunami.
A tropical cyclone is a storm system characterized by a large
low-pressure center and numerous thunderstorms that produce
strong winds and heavy rain.
“Tropical”comes from the fact that they usually develop in the
tropics, while “cyclone” comes from their typical shape: a round
amount (group) of rotating clouds and winds surrounding a clear
area in the center, known as “eye”.
Tropical cyclones are seasonal. In the northern hemisphere the
season is usually from August-November. In the southern
hemisphere the hurricane season is usually between March-May.
According to their winds speed, tropical cyclons
are clasiffied into three types:
If the wind speed is lower than 63 kph, then the
cyclone is known as tropical depression.
If it is between 63 and 118 kph, then it is called
tropical storm.
If its wind speed is higher than 118 kph, then the
cyclone is considered a hurricane.
The high insolation of the zones between tropics increases the
ocean’s temperature, making a lot of water to evaporate, mainly at
the end of the summer. The air above the ocean is heated too
and, as a result, convenction currents start when the air moves
from the cool zones, which have high atmospheric pressure, to
the hot ones. These currents, combined with high evaporation,
promote the formation of big storm clouds, which start spinning
due to air currents and the Coriolis effect.
As the pressure in the center
drops, the cyclone grows. If the
cyclone grows enough, in the
center it develops a low pressure
clear area known as “eye”, due to
the rotational forces that prevent
anything from staying there.
A typical hurricane structure
Hurricanes are the biggest, strongest and
so, most destructive type of tropical cyclone.
They can reach more than 700 km wide, and
have wind speeds over 300 kph.
For this reason, it isn´t odd that they are
one of the most destructive natural
disasters. It is estimated that about 10.000
people die every year due to tropical
cyclones some of which are hurricanes
Hurricanes destructive effects are mainly caused
by:
-Theirs strong, fast winds, that can reach speeds
over 200kph.
-Theirs heavy rainfalls, very likely to cause floods.
-The possibility to create tornadoes as a result of
the pressure differences inside the storm.
-The increase in the sea level when landfalling,
which causes floods and can cut off scape routes.
One good example of a highly destructive
hurricane was Hurricane Katrina.
THANK YOU
FOR
LISTENING!
By: Javier Casatorres
Mon-puo Lee Shu
Ana Casas