Transcript Natural Disasters

Natural Disasters
Tornadoes, Flooding, and
Avalanches
Tornado Facts
• Mainly occur east of Rocky Mountains in
US
– Spring/summer
• 800 tornadoes reported nationwide
• Speeds up to 250 MPH; damage paths 150 miles long
Tornadoes – What Causes Them?
• Develop in warm, moist air as they are met
with cold fronts
• Creates atmospheric instability, which
causes a spinning updraft
Supercell Thunderstorms
• Long line of thunderstorms whose
updrafts/downdrafts are in perfect balance
• Deadly: Perfect conditions for many
tornadoes
Wall Cloud
• Rain-free clouds that accompany tornadoproducing thunderstorms
Waterspouts
• Tornadoes that form
over water
The “F” Scale
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F0: Winds less than 73 MPH
F1: 73-112 MPH
F2: 113-157 MPH
F3: 158-206 MPH
F4: 207-260 MPH
F5: 261-318 MPH
Floods
• Most often, caused by overflow of
rivers/lakes for a variety of reasons
• Farmhouses, vehicles and farmland ruined
• Can contaminate water
Why Live Near Water?
• Humans value the proximity to water
• Land cost is cheaper near water; easier
access to transportation
Flood Control
• Levees/Reservoirs
• In emergencies, sandbags
Benefits of Flooding
• Egypt benefits from silt/clay deposits; soil
becomes very fertile
• Indus/Ganges in Bangladesh
• Humans thrive off of rich soil for crops
Deadliest Flood
• China Flood, 1931
• Est. deaths: 400,000-4,000,000
• Left 80,000,000 homeless
Three Gorges Dam
• Built to help control flooding and control
China’s 3 main rivers