Transcript Natural Geologic Hazards

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 $3.9billion
http://highered.mcgrawhill.com/sites/0072402466/student
_view0/chapter16/animations_and
_movies.html#
Some Earthquake damage
• Paso Robles, 2004
• Loma Prieta, 1989
• Northridge, 1994
http://earthquake.usgs.gov/eqce
nter/recenteqsus/
Earthquake theory
http://earthquake.usgs.gov/eqcenter/re
centeqsus/
• Stresses build up
due to plate motion
• Rocks distort and
store more energy
• Rocks rupture, an
earthquake occurs
• Final offset along
the fault
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
• Mt. Lassen vents
• Hawaiian volcanic
flow
• Hawaiian
Visitor’s
http://www.sci.sdsu.edu/volcano/
Center
Volcano Cross section
Partial 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/visua
lization/collections/tsun
ami.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
http://www3.interscience.wiley.com:8100/legacy/college/strahler/04712380
07/animations/ch15_animations/animation1.html
• 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…)
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
B
C
D
Cross section of beach cliff
Wave begins undercutting the base of a cliff
Cliff falls due to removal of supporting base
Newly exposed cliff is subject to ongoing erosional attack