Catastrophic Events

Two Categories of Catastrophic EventsWeather Related

TornadosHurricanesFloodingWildfires

Tectonic RelatedEarthquakesVolcanoesTsunamis

TornadoTornado (a.k.a twister, cyclone)

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 pm2. Travel 4 miles3. Be 300-400 m wide4. Travel 25-40 mi/hour5. Have wind speeds up to 300 mi/hr6. Produce extremely low pressure7. Be dark due to debris picked up

Safety Rules Rule #1: Take

immediate action! Move away from

tornado’s pathTornado’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 FactsTornados can occur almost anywhere in the worldDuration: a few minutesDiameter (Avg.): 0.4 kmLength of path (Avg.): 6 kmFunnel can travel from 0 mph up to ~70 mph, usually travels at 30 mph99% of all tornados in Northern Hemisphere rotate counterclockwiseTexas 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 structureOne 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 towncarried a necktie rack with 10 ties attached 40 milescarried a flour sack 110 miles from a mill Tornados also drive objects into other objects and have:

Driven splinters into an iron fire hydrantDriven straw and grass into telephone poles

When Tornados Occur

Anytime of the year- usually in the spring, summer, and fallMost tornados occur during late spring in the month of MayBetween the late afternoon and early evening is when most tornados are spawnedThe 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 damageDamage: tree branches snapped, chimneys toppled, signs torn down

F3 Category

(Strong) winds: (158-206) mph, severe damageDamage: most trees uprooted, trains overturned, roofs torn off, walls demolished

F5 Category

(Violent) winds: (261- 319) mph, incredible damage; rareDamage: bark peeled off trees, houses lifted off foundations,

vehicles travel greater than 100 m through the air

Tropical Tropical CycloneCycloneNicknamesNicknames

1. Atlantic: hurricane2. SE Asia, Japan: typhoon3. Australia: willy-willy4. Indian Ocean: cyclone

Tropical Tropical CycloneCyclone

Rated by wind speed (category 1 to 5)Starts and grows over warm ocean waterComposed of bands of thunderstorms spiraling counterclockwise around a low pressure center

What is a hurricane?Violent cyclonic storm that develops in the tropical regionWind 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?

Warm ocean temperatures (>80˚ F) up to 60m deepLittle to no wind shearLow pressure system at least 5˚ North or South of EquatorRotation caused by winds

Source: http://lwf.ncdc.noaa.gov/oa/reports/fran/fran.html

Characteristics Several hundred miles wide Last many days (even weeks) Winds from 74-200 mi/hr Contains an “eye”

a. Small region of low pressureb. Surrounded by highest windsc. Calm, peaceful, sunny weatherd. 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?

June 1st throughNovember

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 Depressionclosed 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

HurricaneEye is developed, winds > 74 mph

What is the Scale Used to Categorize Hurricanes?

Saffir-Simpson ScaleCategor

yMax 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 (13-18)

5 > 155 < 920 > 5.7 (>19)Source: http://kids.earth.nasa.gov/archive/hurricane/saffir-simpson.html

What causes the damage in a hurricane?

WindsFloodingStorm 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 HurricanesIn 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. Up to 20 in. of rainb. 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 TectonicsThe Earth’s crust and upper mantle are broken into sections called platesPlates move around on top of the mantle like rafts

3 types of Plate Boundaries

Divergent BoundariesConvergent BoundariesTransform Fault Boundaries

Divergent BoundariesBoundary between two plates that are moving apart or rifting

RIFTING causes SEAFLOOR SPREADINGCausing Volcanic activity

Mid Ocean Ridge

Convergent BoundariesBoundaries between two plates that are colliding

Creating Subduction ZonesCausing 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 EruptionsDuring 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 VolcanoesDifferent types of volcanic eruptions form different types of volcanoes.Cinder conesShield volcanoesComposite volcanoes

Shied volcanoCan be 28,000 ft Composite volcano

up be 8,000 ft.

Cinder volcanoUp 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 SafetyVolcanoes 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 planListen to warnings

Transform Fault Boundaries

Boundary between two plates that are sliding past each otherEARTHQUAKES 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 SeismographInvented 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

SeismologistsSeismologists 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 ScaleThe amount of damage created by an earthquake depends on several factors.The earthquake’s strengthThe kind of rock and soil that underlie an areaThe population of the areaThe kind of buildings in the areaThe 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