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Catastrophic Events
Two Categories of Catastrophic Events
Weather Related
Tornados
Hurricanes
Flooding
Wildfires
Tectonic Related
Earthquakes
Volcanoes
Tsunamis
Tornado (a.k.a twister, cyclone)
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Counterclockwise column of rotating air extending from
cumulonimbus cloud
Per square foot, is the most destructive atmospheric
event
Rated by wind speed (F1 to F5) Fujita Scale
“Tornado season” = April, May, June
Tornadoes that form over water are called
“waterspouts”
Behavior of a tornado is unpredictable
Typical tornado will:
1. Occur between 3-7 pm
2. Travel 4 miles
3. Be 300-400 m wide
4. Travel 25-40 mi/hour
5. Have wind speeds up to 300 mi/hr
6. Produce extremely low pressure
7. Be dark due to debris picked up
Safety Rules
Rule #1: Take immediate action!
 Move away from tornado’s path

Tornado’s path
Move away at a right angle
Lie flat in nearest ditch, etc.
At home seek shelter in basement or
under heavy table in middle of house
Tornado
A violently rotating column of
air (vortex), hanging from a
cumulonimbus cloud, with
circulation that touches the
surface of the earth
Tornado Facts
Tornados can occur almost anywhere in
the world
Duration: a few minutes
Diameter (Avg.): 0.4 km
Length of path (Avg.): 6 km
Funnel can travel from 0 mph up to ~70
mph, usually travels at 30 mph
99% of all tornados in Northern
Hemisphere rotate counterclockwise
Texas is #1 for frequency of tornados per
year
Tornado Myths
A highway overpass is a safe place to
take shelter under during a tornado
Opening windows during a tornado will
help balance the pressure between the
inside and outside of the house and
may prevent destruction of the
structure
One should seek shelter in the
southwest corner of a house or
basement.
Tornado Oddities
Tornados are reported to routinely carry
objects many miles and have:
sucked the frogs out of a pond and
dropped them on a town
carried a necktie rack with 10 ties attached
40 miles
carried a flour sack 110 miles from a mill
Tornados also drive objects into other
objects and have:
Driven splinters into an iron fire hydrant
Driven straw and grass into telephone poles
When Tornados Occur
Anytime of the year- usually in
the spring, summer, and fall
Most tornados occur during
late spring in the month of
May
Between the late afternoon
and early evening is when
most tornados are spawned
The most dangerous time for
formation during evening
hours
A typical late
afternoon tornado
Songer http://www.pitt.edu/~super1/lecture/lec0761/005.htm
Where Tornados Occur
Tornado Alley covers the Great Plains states
Tornado Wind Speed
In 1971, Dr. Fujita
developed a way of
measuring the winds of a
tornado. He reasoned
that there was a link
between wind speed and
the damage caused by a
tornado. There are 6
categories of tornados
(F0 – F5)
F0 Category
(Weak) winds (40-72) mph , little damage
Damage: tree branches snapped, chimneys
toppled, signs torn down
F3 Category
(Strong) winds: (158-206) mph, severe
damage
Damage: most trees uprooted, trains
overturned, roofs torn off, walls demolished
F5 Category
(Violent) winds: (261- 319) mph, incredible damage;
rare
Damage: bark peeled off trees, houses lifted off
foundations, vehicles travel greater than 100 m
through the air
Tropical Cyclone
Nicknames
1. Atlantic: hurricane
2. SE Asia, Japan: typhoon
3. Australia: willy-willy
4. Indian Ocean: cyclone
Tropical Cyclone
Rated by wind speed (category 1 to 5)
Starts and grows over warm ocean water
Composed of bands of thunderstorms
spiraling counterclockwise around a low
pressure center
What is a hurricane?
Violent
cyclonic storm
that develops
in the tropical
region
Wind speeds
are > 74 mph
Source: http://earthobservatory.nasa.gov/
Newsroom/NewImages/images.php3?img_id=680
What conditions must be present for a
hurricane to develop?
Source: http://lwf.ncdc.noaa.
gov/oa/reports/fran/fran.html
Warm ocean
temperatures (>80˚ F)
up to 60m deep
Little to no wind shear
Low pressure system
at least 5˚ North or
South of Equator
Rotation caused by
winds
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Characteristics
Several hundred miles wide
Last many days (even weeks)
Winds from 74-200 mi/hr
Contains an “eye”
a.
b.
c.
d.
Small region of low pressure
Surrounded by highest winds
Calm, peaceful, sunny weather
Last for about 1 hour as hurricane passes by
Rotation and Pressure
In which direction does a hurricane
rotate?
COUNTERCLOCKWISE
Is the barometric pressure inside the
hurricane high or low?
LOW
When is Hurricane Season?
st
1
June
through
November
31st
Hurricane Anatomy
Source: http://hurricanes.noaa.gov/prepare/structure.htm
Inside a Hurricane
Comparison of Terms
Tropical Disturbance
Group of thunderstorms in the tropics that are
present for
at least 24 hours
Tropical Wave
lack of circulation, winds <25 mph and every
direction
Tropical Depression
closed circulation but disorganized, winds at least 25
mph
Comparison of Terms
Tropical Storm
Shower and thunderstorm moves over closed
circulation,
winds greater than 39 mph
Hurricane
Eye is developed, winds > 74 mph
What is the Scale Used to Categorize
Hurricanes?
Saffir-Simpson Scale
Category Max Wind Speed
(mph)
Min. Surface
Pressure (mb)
Storm Surge m
(ft)
1
74-96
> 980
1-1.7 (3-5)
2
97-111
979-965
1.8-2.6 (6-8)
3
112-131
964-945
2.7-3.8 (9-12)
4
132-155
944-920
3.9-5.6 (1318)
5
> 155
< 920
> 5.7 (>19)
Source: http://kids.earth.nasa.gov/archive/hurricane/saffir-simpson.html
What causes the damage in a
hurricane?
Winds
Flooding
Storm Surge
What is a storm surge?
Large wall or
dome of water
that rushes into
the coastline as
a result of a
hurricane
making landfall
To the right are
the areas
affected by
high storm
surges
Souce: http://www.wkrg.com/hurricanecenter/surge/SE.jpg
Danger from Hurricanes
In the US, most
people that die
from hurricanes
are killed by
fresh water
flooding.
Think Back!
Fresh water
flooding was the
number one
cause of death in
the United
States.
Do you remember
from the graph the
number two cause
of death by
hurricane in the
U.S.?
THE WIND!
Take a look at
this piece of
wood that was
driven into the
palm tree.
Safety
Rules
 Prepare for high winds

Prepare for flooding (greatest source of
damage)
a.
b.
Up to 20 in. of rain
Flooding by coastal water
3. Prepare for thunderstorms
 4. Have on hand stored food, water,
blankets, candles, matches, radio, etc.
 5. Seek shelter

Plate Tectonics
What is Plate Tectonics
The Earth’s crust and upper mantle
are broken into sections called
plates
Plates move around on top of the
mantle like rafts
3 types of Plate Boundaries
Divergent Boundaries
Convergent Boundaries
Transform Fault Boundaries
Divergent Boundaries
Boundary between two plates that are
moving apart or rifting

RIFTING causes SEAFLOOR
SPREADING
Causing Volcanic activity
Mid Ocean Ridge
Convergent Boundaries
Boundaries between two plates
that are colliding
 
Creating Subduction Zones
Causing Volcanic Activity
Volcanoes
Magma
Deep within the Earth, under
tremendous pressure and at great
temperatures, rock exists as a hot
liquid called magma. This molten
rock is found in pockets called
magma chambers.
Magma Chambers
Lava
When the magma reaches the surface,
it is called lava.
In some places, lava can build up to
form a cone-shaped mountain.
The opening from which lava erupts is
the vent. Volcanoes often have more
than one vent.
Lava
Volcanic Eruptions
During volcanic eruptions, many rock fragments
are blown into the air. The smallest particles are
called volcanic dust. (less than 0.25 mm)
Volcanic Ash ( 0.25 -5mm) falls to the Earth and
forms small rocks.
Volcanic bombs (a few cm to several meters) are
molten and harden as they travel through the air.
Volcanic dust and ash
Volcanic Bombs
Types of Volcanoes
Different types of volcanic eruptions form
different types of volcanoes.
Cinder cones
Shield volcanoes
Composite volcanoes
Shied volcano
Can be 28,000 ft
Composite volcano
up be 8,000 ft.
Cinder volcano
Up to 1,000 ft.
Volcanic Activity
Volcanoes are rather unpredictable.
Some erupt regularly, others have
not erupted in modern history.
Scientists classify them as active,
dormant or extinct.
Volcano Safety
Volcanoes are impossible to control but there
are some things you can do to help.
Create a disaster plan (emergency plans)
Make reinforcing structures
Build protective walls that move lava away
Evaluate the risk (build in a safer place)
Educate yourself about volcanic hazards
Have an evacuation plan
Listen to warnings
Transform Fault Boundaries
Boundary between two plates that
are sliding past each other
EARTHQUAKES along faults
San Andreas Fault, CA
New Madrid Fault
Earthquakes
Earthquakes
An earthquake is the shaking and
trembling that results from the sudden
movement of part of the Earth’s crust.
The most common cause of
earthquakes is faulting. During faulting,
energy is released. Rocks continue to
move until the energy is used up.
Seismic Risk Map of the U.S.
Tsunamis
Earthquakes which occur on the ocean
floor produce giant sea waves called
tsunamis. Tsunamis can travel at
speeds of 700 to 800 km per hour. As
they approach the coast, they can
reach heights of greater than 20
meters.
Picture of Banda Aceh before and after 2004 Tsunami
The Seismograph
Invented in 1893 by John Milne, a seismograph
detects and measures seismic waves.
A weight attached to a spring remains nearly still
even when the Earth moves. A pen attached to
the weight records any movement on a roll of
paper on a constantly rotating drum. The drum
moves with the Earth and affects the line.
The Seismograph
Seismologists
Seismologists study earthquakes. They can
determine the strength of an earthquake by the
height of the wavy line recorded on the paper.
The seismograph record of waves is called a
seismogram.
The Richter scale is used to calculate the
strength of an earthquake.
The Richter Scale
The amount of damage created by an
earthquake depends on several factors.
The earthquake’s strength
The kind of rock and soil that underlie an area
The population of the area
The kind of buildings in the area
The time at which the earthquake occurs
Volcano and Earthquake Zones
Most major earthquakes and
volcanic eruptions occur in three
zones of the world. Scientists
believe that there is a great deal of
movement and activity in the
Earth’s crust in these three zones.
Ring of Fire
One major earthquake and volcano
zone extends nearly all the way around
the edge of the Pacific Ocean. This
zone goes through New Zealand, the
Philippines, Japan, Alaska and along
the western coasts of North and South
America. The San Andreas fault is
part of this zone.
Mediterranean Zone
A second Major earthquake and
volcano zone is located near the
Mediterranean Zone and extends
across Asia into India. Many countries
in the zone, including Italy, Greece and
Turkey, have violent earthquakes.
Many volcanic eruptions also occur in
this zone.
Mid-Atlantic Ridge Zone
The third major earthquake and
volcano zone extends through
Iceland and to the middle of the
Atlantic Ocean. There is under the
ocean a long range of volcanic
mountains called the Mid-Atlantic
Ocean Range.
Volcanic Zones