This document defines tsunamis as immense ocean waves triggered by earthquakes, volcanoes, or landslides that can travel long distances and flood coastlines. It lists the major types of geological hazards as earthquakes, volcanoes, landslides, and tsunamis. Earthquakes occur along faults from plate tectonic movement, while volcanoes form at plate boundaries from magma. Landslides and mass wasting endanger hillsides, and tsunamis can cause devastating damage from flooding. While natural hazards cannot always be prevented, their impacts can be reduced through measures like early warning systems, hazard-resistant infrastructure, and land use planning.

1. Geography
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Geological And Natural Hazards
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2. Objectives:
 Define the terms tsunami.
 List major types of geological hazards and describe ways to mitigate their
impacts.
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3. 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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4. 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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5. 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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6. 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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7. 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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8. 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 super volcano
– Past eruptions were so massive they covered much of
North America in ash
– The region is still geologically active
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9. 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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10. Mass wasting events can be colossal
and deadly
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11. 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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12. 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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13. 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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14. 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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