natural disasters
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Natural Disasters. Major Concept: Earth is a dynamic planet How do physical events in the environment affect our health. - PowerPoint PPT PresentationTRANSCRIPT
Natural Disasters
Major Concept:• Earth is a dynamic planet• How do physical events in the environment
affect our health
Although we cannot prevent most natural disasters, there are steps that scientists, engineers, governments, and citizens can take to resist damage and deal with the aftermath.
A landslide caused by the Great Sichuan Earthquake in Sichuan Province, China
EarthquakesEarth’s crust is broken
into large pieces called tectonic plates, which float on a layer of molten rock.
The plates move in different directions
Earthquakes tend to occur along active plate boundaries.
Earthquakes can damage structures and trigger landslides and tsunamis.
Plate TectonicsPlates move at the rate of a few centimeters per year – about the same rate as your fingernails grow.
Asthenosphere convection currents cause the continental plates to move
Plate TectonicsThere are three types of plate boundaries.
Convergent Plate Boundaries
This is when the plates collide
Divergent Plate BoundariesThis is when the plates separate
Transform BoundaryWhen plates slide by each other
California’s San Andreas Fault is a Transform Boundary
San Andreas FaultThe Pacific Plate
(left) west side moves north
The North American Plate (right) east side moves south
WEST
EAST
Oceanic - Oceanic Convergence
Continent - Continent ConvergenceA continent-
continent collision is like a train wreck - both sides end up taking severe damage. Neither side wants to subduct.
The entire Alpine-Himalayan mountain system from Spain to Thailand is behaving this way.
Seismograph
The 1994 Northridge Earthquake
The last major earthquake in Southern California occurred almost twenty years ago
Big quakes release more energy
Earthquakes are found along plate boundaries
Openings in Earth’s crust that eject molten lava and other materials
Ash and gases from volcanic eruptions can block sunlight, causing temperatures to drop.
Eruptions can trigger landslides and mudflows.
Molten lava can cover and destroy surrounding land.
Volcanoes
Did You Know? In 1991, Mount Pinatubo erupted in the Philippines, covering the area around the volcano with a layer of volcanic
materials up to 180 m (600 ft) thick.
VolcanoesMost of the Earth’s active volcanoes on land are located around the Pacific Rim
“Hot Spots”Hawaii and Yellowstone
StormsA storm is a violent disturbance in the
atmosphere4 major types of storms:
ThunderstormsTornadoesHurricanesWinter Storms
A meteorologist is a scientist who studies weather and tries to predict it
Storms
Tornadoes: Rotating funnels of air that can travel over 400 km (250 mi) per hr
Hurricanes: Storms that form over tropical oceans, with winds over 119 km(74 mi) per hour
Thunderstorms: Produce lightning and thunder, usually with heavy rain Did You Know? Hurricane Katrina, which struck
New Orleans in 2005, caused more than $80 billion in damage and killed 1800 people.
ThunderstormsA thunderstorm is a small storm often
accompanied by heavy precipitation and frequent thunder and lightning.
Form in large cumulonimbus clouds (also called thunderheads) on hot, humid afternoons
ThunderstormsWarm, humid air rises
rapidly and the air cools, forming dense thunderhead clouds
Heavy rain falls, sometimes along with hail
Within the thunderhead cloud there are strong updrafts and downdrafts
ThunderstormsLightning heats the air to 30,000oCThunder is the sound of the rapidly heated
air expanding suddenly and explosivelyLight travels faster than sound so you see
lightning before you hear thunder
LightningLightning is a sudden spark, or
electrical dischargePositive and negative charges jump
between parts of a cloud, or between nearby clouds, or between a cloud and the ground
Calculating Lightning DistancesWatch the sky for a flash of
lightning. Count the number of seconds until
you hear thunder. Divide the number of seconds by 5
to calculate the distance the storm is away from your location in miles (or divide by 3 for kilometers).
TornadoesA tornado is a rapidly whirling, funnel-
shaped cloud that reaches down from a storm cloud to touch Earth’s surface
Tornado FormationWarm, moist air flows in at the bottom of a
cumulonimbus cloud and moves upwardA low pressure area forms inside the cloudWarm air rotates as it meets winds blowing
in different directions at different altitudes
Tornado Alley is an area of the United States that has a high frequency of tornadoes because cold, dry air moves south from Canada to meet warm, humid air from the Gulf of Mexico
5 states that cross Tornado Alley are:TexasOklahomaKansasNebraskaIowa
The Fujita Tornado Damage ScaleTornadoes are ranked on the Fujita scale by
the amount of damage they cause
Tornado SafetyA tornado watch is an announcement
that tornadoes are possible in your area. Stay tuned to the radio or television news.
A tornado warning is an announcement that a tornado has been sighted. Take shelter immediately!
The safest place to be during a tornado is in a storm shelter or the basement of a well-built building
Hurricanes A hurricane is a tropical cyclone that has winds of 119 km/h or
higher Hurricanes form in the Atlantic, Pacific, and Indian Oceans In the western Pacific Ocean, hurricanes are called typhoons A hurricane begins over warm ocean water as a low-pressure
area, or tropical disturbance. A hurricane draws its energy from the warm, humid air at the
ocean’s surface As the air rises and forms clouds, more air is drawn into the
system Inside the storm are bands of very high winds and heavy rains Winds spiral inward toward the area of lowest pressure at the
center
Hurricane Formation
HurricanesHurricanes last longer than other storms, usually
a week or moreAfter a hurricane passes over land, it no longer
has warm, moist air to draw energy from so it loses strength
A storm surge is a “dome” of water that sweeps across the coast where a hurricane lands
For safety during a hurricane, people are told to evacuate
Evacuate means to leave the area immediately
Winter StormsAll year round, most precipitation begins in
clouds as snowA large amount of humid air that cools below
0oC can produce a winter stormBlizzard = Blowing snow and reduced visibilityMain Hazards
Vehicle accidentsHypothermiaExertionImmobility
Avalanches
Masses of snow that slide down a slopeConditions favoring avalanches:
Slope greater than 30 degreesUnstable snowpackHeavy snowfallWarm temperatures
Did You Know? A big North American avalanche can contain 230,000 m3 of snow—about the equivalent of 20 football fields filled with snow 3 m (10 ft) deep.
ImpactsMain direct impacts
are deaths, injuries, and economic losses to communities affected.
Indirect impacts include wider economic losses to tourism industry, transport delays, and wider spatial economic losses.
Contributing factorsHeavy rainfall on snow
(more likely in Scotland than the Alps!)
Deforestation - reducing slope stability
Vibrations – skiers or more dangerous earth movements
Long cold winters then heavy snow falls in spring. i.e. slip plane created.
Snow-pack StressSnow lying on a slope is subject to stress : gravity is pulling it downwardsadhesion and weight is keeping it “stuck” to the
slope.Often these stresses are delicately balanced, and a
slight change can bring about failure, particularly where the snow-pack is under tension.
Powder snow avalanches
No warning.Up to 200mphUp to 50
tons/m 2 forceOccur at any
time in season.Example :Galtu
r, Austria.
Wet snow avalanchesUsually late in
season.Slow moving (5-
15mph).Considerable
weight of wet snow (up a million tonnes).
Example : Odda, Norway.
Slab avalanchesSlab avalanches
are most common occurrence.
Often started by human error.
Most frequent cause of death amongst skiers, snowboarders, and power-skiers.
Speeds up to 100mph.