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AP Environmental
Science
Mr. Grant
Lesson 21
Earth’s Physical Systems:
Matter, Energy, and Geology
Geological And Natural Hazards
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Objectives:
• Define the terms tsunami.
• List major types of geological hazards and describe ways
to mitigate their impacts.
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Define the terms tsunami.
Tsunami: An immense swell, or wave, of ocean water
triggered by an earthquake, volcano, or landslide, that
can travel long distances across oceans and inundate
coasts.
Japan Tsunami (March 2011)
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List major types of geological hazards and describe
ways to mitigate their impacts.
• The circum-Pacific belt, or “ring of fire”, spawns most of the
world’s volcanoes and earthquakes.
• Earthquakes result from movement at faults and plate boundaries.
We cannot prevent them, but we can build structures and cities in
safer ways.
• Volcanoes arise from heating by magma at rifts, subduction
zones, or hotspots.
• Landslides and other forms of mast wasting can occur on small
or large scales; damage can be minimized by understanding their
risks.
• Tsunamis can flood coastlines and cause immense damage.
Early warning systems will be key in minimizing future losses.
• We often worsen impacts from natural hazards, but we can
reduce them through better land use practices.
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Geologic and natural hazards
• Some consequences of plate tectonics are hazardous
• Plate boundaries closely match the circum-Pacific belt
- An arc of subduction zones and fault systems
- Has 90% of earthquakes and 50% of volcanoes
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Earthquakes result from movement
• Earthquake = a release of energy
(pressure) along plate boundaries
and faults
• Can be caused by enhanced
geothermal systems
- Drill deep into rock, fracture it
- Pump water in to heat, then
extract it
• Can do tremendous damage to life
and property
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Buildings can be
built or retrofitted
to decrease damage
Volcanoes
• Volcano= molten rock, hot gas, or
ash erupts through Earth’s surface
- Cooling and creating a
mountain
• In rift valleys, ocean ridges,
subduction zones, or hotspots
(holes in the crust)
• Lava can flow slowly or erupt
suddenly
• Pyroclastic flow: fast-moving
cloud of gas, ash, and rock
- Buried Pompeii in A.D. 79
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Volcanoes have environmental effects
• Ash blocks sunlight
• Sulfur emissions lead to sulfuric acid
- Blocking radiation and cooling the atmosphere
• Large eruptions can decrease temperatures worldwide
- Mount Tambora’s eruption caused the 1816 “year
without a summer”
• Yellowstone National Park is an ancient supervolcano
- Past eruptions were so massive they covered much
of North America in ash
- The region is still geologically active
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Landslides are a form of mass wasting
• Landslide = a severe, sudden mass wasting
- Large amounts of rock or soil collapse and flow
downhill
• Mass wasting = the downslope movement of soil and
rock due to gravity
- Rains saturate soils and trigger mudslides
- Erodes unstable hillsides and damages property
- Caused by humans when soil is loosened or exposed
• Lahars = extremely dangerous mudslides
- Caused when volcanic eruptions melt snow
- Huge volumes of mud race downhill
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Mass wasting events can be colossal and
deadly
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Tsunamis
• Tsunami = huge volumes of water are displaced by:
- Earthquakes, volcanoes, landslides
• Can travel thousands of miles across oceans
• Coral reefs, coastal forests, and wetlands are damaged
- Saltwater contamination makes it hard to restore
them
• Agencies and nations have increased efforts to give
residents advance warning of approaching tsunamis
- Preserving coral reefs and mangrove forests
decreases the wave energy of tsunamis
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One dangerous tsunami
• On December 26, 2004 an earthquake off Sumatra
triggered a massive tsunami that hit Indonesia,
Thailand, Sri Lanka, India, and African countries
- Killed 228,000 and displaced 1–2 million more
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We can worsen impacts of natural hazards
• We face and affect other natural hazards: floods, coastal
erosion, wildfire, tornadoes, and hurricanes
• Overpopulation: people must live in susceptible areas
• We choose to live in attractive but vulnerable areas
(beaches, mountains)
• Engineered landscapes increase frequency or severity of
hazards (damming rivers, suppressing fire, mining)
• Changing climate through greenhouse gases changes
rainfall patterns, increases drought, fire, flooding, storms
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We can mitigate impacts of natural hazards
• We can decrease impacts of hazards through
technology, engineering, and policy
- Informed by geology and ecology
• Building earthquake-resistant structures
• Designing early warning systems (tsunamis, volcanoes)
• Preserving reefs and shorelines (tsunamis, erosion)
• Better forestry, agriculture, mining (mass wasting)
• Regulations, building codes, insurance incentives
discourage developing in vulnerable areas
• Mitigating climate change may reduce natural hazards
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