Natural Geologic Hazards
A visual tour of worldwide natural geologic hazards
Earthquakes
• Earthquakes can be powerful movers of the Earth’s crust
• Annual cost of damages in the US alone is $3.9billionhttp://highered.mcgraw-hill.com/sites/0072402466/student_view0/chapter16/animations_and_movies.html#
Some Earthquake damage
• Loma Prieta, 1989
• Paso Robles, 2004
• Northridge, 1994
http://earthquake.usgs.gov/eqcenter/recenteqsus/
Earthquake theory
• Stresses build up due to plate motion
• Rocks distort and store more energy
• Rocks rupture, an earthquake occurs
• Final offset along the fault
http://earthquake.usgs.gov/eqcenter/recenteqsus/
Volcanic Eruptions
• There are approximately 3000 active volcanoes
• About 50 volcanoes erupt every year
• 80,000 people have been killed by volcanoes since 1900
• Mt. St. Helens caused about $1billion in damage
• Hawaiian volcanic flow
• Mt. Lassen vents
• Hawaiian
Visitor’s
Center
http://www.sci.sdsu.edu/volcano/
Volcano Cross sectionPartial melting of rock occurs at subduction and
divergent plate boundaries and at hot spots*• Magma flows upward through weaknesses in
the lithosphere
Tsunami
• Tsunami hit California coastlines in 1946, 1952, 1957, 1960 and 1964
• Over 80 tsunami have been reported in the last 100 years
• Damage estimate for the 1964 tsunami was over $10million.
• Crescent City Tsunami, April, 1964
• Banda Ache devastation, Dec 24, 2004
Tsunami formation
• Ocean floor before the earthquake
• Earthquake occurs. Faulting pushes Earth upwards
• Tsunami is generated. Waves move outward.
• Tsunami wave height grows towards shore
http://serc.carleton.edu/NAGTWorkshops/visualization/collections/tsunami.html
Landslides
• Aka mudslides. avalanches, hillside creep, lahars
• Can be fast or slow, dry or watery
• Average US annual losses are $2billion and 25 ~ 50 deaths
Evolution of Landslides
• Landslides occur due to gravity pulling weak material downhill
• Steeper slopes = greater downward pulling-effect
• Weakened rock enhances potential of sliding (rain, water, earthquakes, volcanic blasts, ice, weight etc…)
http://www3.interscience.wiley.com:8100/legacy/college/strahler/0471238007/animations/ch15_animations/animation1.html
Coastal Erosion• 85% of California’s
shoreline is actively eroding
• El Nino winter poses the greatest threat to coastlines due to increased storms
• Ca damages of $116million for the winter of ’82~’83
Coastal erosion
Processes of Coastal Erosion
A Cross section of beach cliff
B Wave begins undercutting the base of a cliff
C Cliff falls due to removal of supporting base
D Newly exposed cliff is subject to ongoing erosional attack
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