Chapter 16: Chance and Catastrophes

Hazards, Disasters, and Catastrophes

• Natural processes are physical, chemical, and biological changes that modify the landscape.– Common denominators of vastly destructive

natural events are transport of material (water, air, and earth) and expenditure of energy.

Earthquake

• Earthquakes result when the rocks that are under stress from the internal earth processes that produce our continents and ocean basins rupture.– mostly at depths of 10 to 15 km along faults

• Earthquakes release vast amounts of energy.– they can release more energy than a large

nuclear explosion.

Volcanic Eruption

• Volcanoes are the result of extrusion at the surfaces of molten rock (magma). – May be explosive and violent, or they may be less

energetic lava flows.

– Generally occur at boundaries between tectonic plates

– Some volcanoes also occur in more central parts of tectonic plates where hot spots deep below heat the rocks.

• E.g. Yellowstone National Park and the Hawaiian Islands.

Landslides

• A general term for the down slope movement of soil and rock. – Occur when the driving forces that tend to move

materials down a slope exceed the resisting forces that hold the slope material in place.

– Resisting forces are produced by the strength of the material on slopes.

– The dominant driving force on slopes is the weight of slope materials influenced by the force of gravity. The steeper the slope and the heavier the slope materials, the greater the driving forces.

Landslides

– Human processes that add to or increase the slope angle increase the drive forces.

– Resisting forces reduced by increasing the amount of water on or in a slope, or by removing vegetation that reduces the root strength of the soil or rock.

Hurricane

• A hurricane is a tropical storm with circulating winds in excess of 120 km (74 mi) – Move across warm ocean waters of the tropics.

• Hurricanes gather and release huge quantities of energy– Water is transformed from liquid in the ocean

to vapor in the storm

Tsunami

• A series of large ocean waves produced after the ocean water is suddenly disturbed vertically by processes such as – Earthquakes, volcanic eruptions, submarine

landslides, or the impact of an asteroid or comet– Over 80% of all tsunamis are produced by

earthquakes.

Wildfire

• A rapid, self-sustaining, biochemical oxidation process that releases light, heat, carbon dioxide, and other gases and particulates into the atmosphere.

• Fuel is rapidly consumed during wildfires – helps maintain a balance between plant productivity

and decomposition in ecosystems.

• The primary cause is vegetation built up– When microbes are not able to decompose plants fast

enough to balance the carbon cycle.

Tornado

• A tornado is a funnel-shaped cloud of violently rotating wind – Extends downward from large cells of thunderstorms to

the surface of Earth. – May occur when a cold air mass collides with a warmer

one. • Water vapor in the warmer part of the atmosphere is forced

upward where it cools and produces precipitation. • As more warm air is drawn in, the storm clouds grow higher

and thunderstorm activity increases in intensity.

– Tornadoes concentrated in the Plains States

Flood

• The inundation of an area by water.• Produced by a variety of processes ranging from

– Intense rainstorms to melting of snow, storm surge from a hurricane, tsunami, and rupture of flood protection structures, such as levees or dams.

• River flooding– Shapes the landscapes through erosion and deposition.

– Erosion has produced features as small as gullies and as large as the Grand Canyon of the Colorado River.

Heat Wave

• A period of days or weeks of unusually hot weather– A recurring weather phenomenon related to

heating of the atmosphere and the moving of air masses.

• Hypothesized that human-induced global warming has increased the number and intensity of heat waves in recent years.– Now considered the most deadly of all weather

hazards

Drought

• A period of months, or years, of unusually dry weather.– Related to natural cycles of wet years that

alternate with series of dry years. – Thought to be related to the heating of ocean

waters and the moving of major air masses.

Hazards, Disasters, and Catastrophes

• These processes are natural– Become hazards, disasters or catastrophes when

people interact with or live and work where they occur.

• Natural hazard– Any natural process that is a potential threat to

human life and property.

Hazards, Disasters, and Catastrophes

• Disaster– A hazardous event that occurs over a limited

time span in a defined geographic area

• Catastrophe– A massive disaster that requires significant

expenditure of money and time for recovery.

Fundamental Concepts Related to Natural Hazards

• How natural processes and hazards, might be reduced, minimized or eliminated:– Natural processes have service functions.– Hazards are predictable.– Linkages exist between hazards.– Linkages exist between different hazards and

between the physical and biological environment.

Fundamental Concepts Related to Natural Hazards

– Hazards that previously produced mostly disasters are now producing catastrophes.

– Risk from hazards can be estimated.– Adverse effects of hazards can be minimized.

Natural Process Have Natural Service Functions

• Dust storms carry nutrient rich soil

• Landslides may form lakes.

• Physical processes linked to a varied landscape– W/o diversity in land diversity of life would be

reduced.

Linkages Exist

• Understanding the links between hazards and between the physical and biological environment is an important part of understanding the consequences of natural hazard.

• Hazards can be linked– Volcanic eruption-landslides

– Landslides-flooding

– Hurricanes-flooding-landslides

– Submarine earthquake-tsunamis

Linkages exist

• Links to biological environment– Global scale; comet-extinction– Regional scale; hurricane-beach erosion and

vegetation destruction– Wildfires remove vegetation-landslides– Erosion-loss of fish habitat

Risk from Hazards Can Be Estimated

• Acceptable risk– The risk that individuals or society are willing

to take– E.g. millions of people choose to live in CA

even though high probability of earthquakes

Impact and Recovery from Disasters and Catastrophes

• Direct effects– People killed, injured, dislocated, made

homeless or otherwise damaged by the event.

• Indirect event follow a disaster– Donations, shelter, taxes to help finance

recovery and emotional distress.– May effect society as a whole

What does the Future Hold with Respect to Disasters and Catastrophes?

• Anticipating hazards rather than simply reacting to them will help minimize economic losses and reduce pain and suffering.– E.g. large earthquake in China