Natural Disasters

Tornadoes

I. Introduction

Can occur in many parts of the world, but are found most frequently in the US east of the Rocky mountains during spring and summer (typically april-june)

Definition: a violently rotating column of air extending from a thunderstorm to the ground.

Commonly called a twister

FYI: IN AN AVERAGE YEAR, 800 TORNADOES ARE REPORTED IN THE US ALONE RESULTING IN AT LEAST 80 DEATHS AND 1,500 INJURIES

II. What Causes tornadoes? Formed from thunderstorms that are in front of a cold

front moving east. These thunderstorms often produce large hail, strong

winds, and tornadoes. Tornadoes in the late winter, early spring are most often

caused by this particular weather pattern and can occasionally result in large outbreaks

During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.

II. What causes tornadoes Along the front range of the Rocky Mountains, in

the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other conditions are right, these storms can produce tornadoes.

Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore

III. How do Tornadoes form?

Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.

III. How do Tornadoes form?

Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical

III. How do Tornadoes form?

An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation

III. How do Tornadoes form?

A lower cloud base in the center of the photograph identifies an area of rotation known as a rotating wall cloud. This area is often nearly rain-free. Note rain in the background

III. How do Tornadoes form?

Moments later a strong tornado develops in this area. Softball-size hail and damaging "straight-line" winds also occurred with this storm

IV. 3 Classifications of Tornadoes1. Weak• 69% of all tornadoes• Less than 5% of tornado deaths• Lifetime 1-10+ minutes• Winds less than 110 mph

IV. 3 Classifications of Tornadoes2. Strong• 29% of all tornadoes• Nearly 30% of all tornado deaths• May last 20 minutes or longer• Winds 110-205 mph

IV. 3 Classifications of Tornadoes3. Violent• Only 2% of all tornadoes • 70% of all tornado deaths• Lifetime can exceed 1 hour• Can cause damage up to 30

miles

FUJITA SCALE OF TORNADO INTENSITY

Rating Wind Speed Damage

F-173 - 112 mph

Rips shingles off roofs; flips mobile homes.

F-2113 - 157 mph

Upturns and flips boxcars.

F-3158 - 206 mph

Exterior walls and roofs blown off homes. Metal buildings collapsed or severely damaged. Forests and farmland destroyed.

F-4207 - 260 mph

Few walls left standing. Large concrete blocks launched far distances.

F-5261 - 318 mph

Homes flattened with all debris removed. Schools, motels, and other larger structures damaged considerably with exterior walls and roofs gone. Top floors demolished.

Facts1. Can occur anywhere2. Can occur anytime3. No place is completely safe from

tornadoes

Recall: If there are more than 800 a year, why don’t we know about that many?

V. Impact on Environment No known positive impacts Because tornadoes often cause

destruction no matter how big or small it is, there are several environmental concerns 1. Harmful substances can be released

or emissions released in brush fires 2. Soil erosion, water pollution 3. If an area that is older that contains

asbestos or lead paint, can cause severe problems for humans and wild life

Hurricanes

I. How do Hurricanes Form? Hurricanes usually form in the summer

or early autumn when several key atmospheric ingredients come together

Common Name: Cyclone MYTH: HURRICANES ONLY NEED WARM

WATER TO FORM IF THIS WERE TRUE, HURRICANE SEASON

WOULD BE ALL YEAR LONG IN THE TROPICAL REGIONS

II. Conditions for Hurricane Formation• 1. Pre-existing Disturbance or low

pressure area must have formed in the low levels of the atmosphere to start winds converging and uplift.

• 2. Warm Water to a sufficient depth to support the energy that a hurricane will need. The temperature needs to be about 26.5º Celsius or 80º Fahrenheit to a depth of about 50 meters or 150 feet deep.

II. Conditions for Hurricane Formation• 3. Low Stability will allow deep convection or

cumulonimbus clouds to build to great heights in the atmosphere. A stable air mass will inhibit cloud development and not allow for significant cloud growth to support the deep convection needed for a hurricane to develop.

• 4. Coriolis Force The disturbed area of weather needs to be at least 4-5º away from the equator. This is the approximate distance from the equator for the Coriolis force to achieve a gradient wind balance to sustain the low pressure area. FYI: CORIOLIS FORCE IS A

FORCE THAT IS DEFLECTED FROM ITS PATH AND IS A RESULT OF THE EARTH’S ROTATION

II. Conditions for Hurricane Formation• 5. Moist Mid Level of the atmosphere. If there is

dry air aloft it will weaken or choke off the updrafts in the cumulus clouds.

• 6. Low Vertical Wind Shear from the surface to upper troposphere. This allows for the thunderstorm clouds to build to great heights. If the wind speed increases or changes direction with height, the cumulonimbus clouds get deformed can not sustain the hurricane heat engine.

• 7. Divergence in the upper Atmosphere allows for the transport of mass away from the hurricane.

III. Hurricane Strength Chart Known as the: Saffir-Simpson Hurricane

Scale Category One Hurricane (Sustained

winds 74-95 mph, 64-82 kt, or 119-153 km/hr). Very dangerous winds will produce some

damage

III. Hurricane Strength Chart- Category Two Hurricane (Sustained

winds 96-110 mph, 83-95 kt, or 154-177 km/hr). Extremely dangerous winds will cause

extensive damage Category Three Hurricane (Sustained

winds 111-130 mph, 96-113 kt, or 178-209 km/hr). Devastating damage will occur

III. Hurricane Strength Chart- Category Four Hurricane (Sustained

winds 131-155 mph, 114-135 kt, or 210-249 km/hr). Catastrophic damage will occur

Category Five Hurricane (Sustained winds greater than 155 mph, greater than 135 kt, or greater than 249 km/hr). Catastrophic damage will occur

Recent Hurricanes Hurricane Irene: category 3, made

landfall as a 1 Hurricane IKE: category 4, made landfall

as a strong 2 Hurricane Katrina: category 5, made

landfall as a strong 3

Environmental Impact In addition to impacting individuals, homes,

and communities, hurricanes also have a profound effect on the environment, especially estuarine and coastal habitats.

Hurricanes generate strong winds that can completely defoliate forest canopies and cause dramatic structural changes in wooded ecosystems.

Animals can either be killed by hurricanes or impacted indirectly through changes in habitat and food availability caused by high winds, storm surge, and intense rainfall

Earthquakes, Tsunamis & Flooding

I. What is an earthquake?An earthquake is what happens when

two blocks of the earth suddenly slip past one another.

The surface where they slip is called the fault or fault plane.

The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.

II. What causes an earthquake? There are many tectonic plates across

the earth surface, like a puzzle Where they are joined are called fault

lines They sit on mantle (lava) so they can

move around. The edges are rough so they sometimes get stuck. When they come unstuck the plates shake which causes an earthquake

III. How are earthquakes measured? The richter scale Each level on the richter scale is 10

times that of the previous level earthquakes in the last 30 days

IV. Recent Earthquakes Haiti (2010)-7.0 magnitude Japan (2011)-9.0 magnitude

FYI a magnitude 8.0 earthquake releases the energy of 6 million tons of TNT….

V. Environmental Impacts Human casualties and injuries as a result of the

infrastructure collapsing are the immediate concerns after a devastating earthquake.

Ecosystems and habitats are also impacted by earthquakes. For example, 23 percent of the giant panda bear habitat was lost during the Sichuan earthquake of 1976. This area is considered a hotspot for biodiversity since it is home to over 12,000 species of plants and 1,122 species of vertebrates.

Another impact to ecosystems in the wake of an earthquake comes from the resounding tsunamis that can be triggered by these events

V. Environmental Impacts Earthquakes can also cause

environmental concerns that can affect human health.

Aside from the devastation caused by large earthquakes, landslides and aftershocks can affect agricultural land, water sources, and sewage systems.

Debris and waste disposal in the aftermath of an earthquake can cause another concern for human health and the environment.

Tsunami

I. What are Tsunamis? A tsunami is a series of ocean waves

that are generated by a large-scale disturbance of seawater.

Most tsunamis are generated from earthquakes, but they can also occur after volcanic eruptions, landslides and meteor impacts.

Occur most frequently in the Pacific ocean, but can happen in any ocean.

IV. Environmental Impact With obvious devastation to the land,

marine life also gets disturbed Flooding is inevitable and Typhoid Fever

is an issue as well as other risks that come with flooding such as mold, mildew, and water pollution

Whole species can be wiped out as their habitats are destroyed.

V. Discussion Questions 1. How can a disaster cause another

disaster somewhere else? 2. What is the difference between a

hazard and a disaster? 3. How can the actions of humans cause

a disaster?