Natural Disasters Final
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What is a hazard?
A type of threat that hasn't happened yet, but there's potential for some serious damage
What is a natural disaster?
- -Causes significant property damage
- -Kills people
- -A natural event that has a negative effect on humans
What is a great natural disaster?
- -Effects many people
- -Covers a large area
- -Has a long recovery
- -Requires external assistance
What is mitigation?
Activities to reduce losses from future disasters, including prevention and protection
What are the methods of mitigation?
- Alter-modify the hazard
- Adapt-modify structures
- Avert-redirect the hazard
- Avoid-stay away
Who is Alfred Wegener?
He proposed the idea of continental drift and the supercontinent called Pangaea
Who is Harry Hess and Robert Dietz?
They proposed mantle convection, seafloor speaking, and lithospheric plates
What are some of the evidences that Alfred Wegener used and how do they support plate movement?
- -The fit of the continents
- -Matching geology (location of glaciers, fossils, and rock types)
What are some of the modern evidences for plate tectonics and how do they support plate movement?
- -Seafloor spreading
- -Mid ocean ridges
- -Magnetic stripes
What are the layers of the Earth?
- -Inner (solid) and outer core (liquid)
- -Mantle (mesosphere has stiff rocks, asthenosphere is soft plastic, lithosphere is hard like rock)
What are the types of plate boundaries?
Convergent, divergent, transform
What features do you find at each type of plate boundary? Why?
-Convergent (trenches) plates create volcanoes and earthquakes. Divergent plates are mostly volcanoes. (mid ocean ridges) Transform plates earthquakes
- -Convergent: earthquakes are deep and huge, volcanoes are big and dangerous. Means coming together
- -Divergent: earthquakes are weak and shallow, volcanic activity is mild. Means going away
- -Transform: earthquakes are shallow and intermediate strength, no volcanoes. Means sliding across
What happens in subduction zones? AKA convergent plates
-Largest earthquakes, tsunamis, volcanoes
What is a hypocenter/focus?
Point where initial rupture occurs beneath the surface of the fault
What is an epicenter?
Point on earth's surface directly above focus, usually not on the fault
What is a scarp?
Where the fault plane broke the earth's surface, exposed area
What are the different fault types?
- -Normal fault: hanging wall moves down(divergent)
- -Reverse/thrust fault: hanging wall moves up (convergent)
- -Strike-slip fault: hanging wall moves laterally(transform)
How do you distinguish between a right and left lateral strike-slip?
- -Stand on a fault
- -Look down the fault line
- -What side moved toward you
What are the four types of waves? How are they different?
- Body Waves:P waves-parallel and compression called primary, moves 6km/s
- S waves-shear waves, called secondary, moves perpendicular to the wave, travels 3km/s
- Surface WavesLove waves-side to side movement, bad for buildings, most destructive
- Rayleigh waves-rolling surface, moves up and down
What is elastic rebound theory?
- The earth builds up energy and nice it is released the earth can't reset
- Ex. Rubber band
What are the main factors that contribute to shaking?
L and R waves
What does magnitude measure? How is it measured?
- -Richter scale or seismograph
- -Based on wave amplitude and ground displacement
What are the differences between Richter and Moment scales?
Richter scales are based on wave amplitude and ground displacement while moment scales are based on rupture dimensions
How do we triangulate earthquakes?
Calculates where the earthquake started by looking at 3 points
How does liquefaction occur?
- -Related with earthquakes
- -Water ills in the pore space between grains and eliminates all grain to grain contact
- -Whatever is on top will sink
- -Ground behaves like a liquid
- -Things less dense will rise
What are the key ingredients to liquefaction?
How does tsunamis, fires, and landslides relate to earthquakes?
-Ground shakes and cause land to move, tsunami's because of displace of the seafloor, fires due to breaking of gas pipes
What are the factors that affect shaking in earthquakes?
- -Distance to epicenter/fault
- -Depth of focus (hypocenter)
- -Direction of rupture
- -Local geology
What are the building types we discussed and how can you identify each of them?
- Unreinforced masonry buildings (old brick buildings)- Brick pattern, narrow windows
- Soft story (garage story)- Built on stilts or a garage
- Modern seismically safe home- Modern homes are up to code
What are the three types of volcanic rocks?
- Rhyolite-lighter color cause of iron, more silica Andesite-medium iron and silica
- Basalt-less silica, darker color
What is viscosity?
-The resistance to flow
What causes high viscosity?
High silica and lower temperatures
What causes an explosive volcanic eruption?
Viscous magma and high volatile content
Describe a composite volcano
- -High viscosity
- -High volatiles
- -High volume
Describe a shield volcano
- -Low viscosity
- -Low volatile
- -Large volume
Describe a cinder cone
- -Moderate viscosity
- -Moderate volatile
- -Low volume
Describe a lava dome
- -High viscosity
- -Low volatile
- -Low volume
What rock features could you get from a spatter cone?
- Low, steep sided hills or mound of welded lava fragments
- -Low viscosity, lots of gas
What is ash?
- -Broken up rock
- -It’s like sand and glass
What are the signs of an impending eruption?
- -Changes in gas emission
- -Ground bulging
- -temperature increase
What are lahars?
Snow melts and ash mixes with it
What are pyroclastic flows?
-Big explosion where the ash falls into the air
What are fumeroles?
Describe the case study of Kratkatau
- -Loudest sound ever (Heard over 2,000 miles away)
- -Vibrant sunsets
- -Led to Munch painting "The Scream"
- -Global temperature dropped by 2 degrees
- -Shock wave traveled the earth 7 times
Describe the case study of Eyjafjallajokull
- -No flights for about a week
- -Cost airlines about $1.7 billion
Describe the case study of Pinatubo
-Thousands saved due to forecast
Describe the case study of Mt. Tambora
- -Located by a subduction zone
- -Largest eruption in recorded history
- -Caused year without a summer
- -Mary Shelley wrote Frankenstein
- -Joseph Smith Senior moves to New York
Describe the case study of Versuvius
-Pryroclastic flow was a problem
Describe the case study of Rainer
-Lahars was a problem
How do you classify a landslide?
What is the rock and how did it move and how fast is it moving
What are the classifications of landslides?
- Slides:Slump- slow
- Glide- rapid
- Flow:Avalanche- very fast
- Creep- extremely slow
- Fall:Rockfall-extremely rapid
What is the factor of safety and how is it calculated?
- -It is one magic number
- -If it's above 1 then it stays
- -If it moves below one it moves
- -Factor of Safety = Resistance Force/Driving Force
What are the factors that contribute to landslides?
- -Dipping beds (rocks that are flat but tilted)
- -Saturated soil
- -Steep slopes
- -Lack of vegetation/rock/soil type
What are bedding planes?
Ancient fault surfaces which are weakness planes
What are daylighted beds?
When the beds are exposed
How does water affect the stability of a slope?
- -Water is heavy and adds weight
- -It forces particles apart like air hockey
- -Allows for material to flow
What is the role of the angle of repose?
- -It is the angle that the slope can handle before it falls
- -Sand is 35 degrees
What is the role of vegetation in slope stability?
- -It holds soil and rocks in place
- -They remove water from the slope
What is water infiltration?
- -Watering the grass starts to saturate the slopes
- -Spring gets the most water in the ground due to snow melting
What is wave undercutting?
-The waves corrode the base of the cliffs causing them to fall
What is frost wedging?
- -A process that occurs in the mountains in the Spring
- -The snow melts and in the day time it expands the rocks causing wedges so the rocks aren't touching anymore and they slide off
Describe the function of clay in landslides
- -The enemy
- -Low strength
- -Very slippery
- -Holds moisture
- -Angle of repose is 9-12 degrees
- -Shale is clay compressed
What does removing the toe do to a slope?
-Toe resists movement so a landslide happens
How can you identify landslides?
- -Hummocky (irregular ground surface)
- -Cracks or terraces (scarps) on hillside
- -Mouth of a canyon
- -Natural springs
What are the methods of mitigation for landslides?
- -Drainage control
- -Slope support/anchors
- -Retaining walls
- -Rock fall netting/mesh
- -Debris flow channels
What are the things necessary to make a good retaining wall?
- -Has to be super strong
- -has to have drains
Describe the case study La Conchita
- -1995 didn't kill anyone
- -2005 killed 10 people
- -Retaining wall didn't hold
- -Filed lawsuit against county
- -15 inches of rain in 15 days
- -Rapid mudflow
Describe the case study of Vajont Dam
- -Italian government
- -Landslide fell into the dam causing water to rise over the dam
- -800 ft wave
- -2,000 deaths
What is base level and why is it important?
- -The lowest elevation to which a river will erode
- -Once it starts reaching base level it will start to meander
What is a drainage basin and what is its effect on flooding?
- -All the little rivers that drain into a big river
- -Bigger drainage basin means bigger flooding
What happens when a river is constricted? Widened?
- -Narrow stream means faster water and more erosion
- -Wider stream means slower water and more deposition
What is discharge?
-Volume of water that flows past a point in a given time
What is gradient?
-The slope of the stream channel
Describe a meandering stream
- -Happens at base level
- -Have good floodplains
What is an oxbow lake?
-Happens when a meandering lake erodes too much
Describe a braided stream
- -Happens at bottoms of mountains
- -Overloaded with sediment
- -Faster water
- -Well defined floodplain
Where does erosion occur in lakes?
-On the outside of the bend
Where does most of the deposits happen in the river?
-On the inside of the bend
What is the outside of the bend called?
Describe flash flood
- -Upstream flood
- -In more mountain area with braided stream
- -Large amounts of rainfall over a short period
- -Water gathers in canyons with high amounts of energy
- -Results in alluvial fan by dumping all the sediment at the bottom of the canyon
Describe regional flood
- -Downstream flood
- -Meandering stream
- -Lots of rain over a large area that increases water levels and can last for weeks
- -Low topography
What is negative feedback?
-When something stops or slows a process
What is positive feedback?
-Something that continues the ongoing bad cycle
What is avulsion?
-River finds a new course
What are levees?
-Barriers to keep the water out
Describe the case study Hannibal, Missouri
- -Planned for 30 ft flood, built 31ft levee
- -River rose to 32 ft
- -Water standing in flood plains 30-60 ft deep
Describe flood frequency
- -The longer the small chance it will happen
- -1 divided by the number year flood
- Example: 50 = 2%; 500 = 0.2%
Describe the case study Yellow River-China's Sorrow
- -It picks up a lot of sediment so it looks yellow
- -High silt conent
- -1887 naturally killed 2,000,000 people
- -Second deadliest natural disaster in history
- -1931 naturally killed about 4,000,000 people
- -Seven cyclones hit in one year
- -Deadliest natural disaster in history
- -1938 Military blows levees to stop Japanese, it didn't work, and they didn't warn their people
- -Killed about 900,000 of their own people
Describe the case study of Johnstown, PA
- -Two rivers surrounding city
- -Dam failed due to
- -Hunting and fishing club in charge of it, but didn't take care of it
- -Put up mesh net to catch fish but it blocked the spillway
- -Sold drainage pipes
- -Shaved the top of the dam for their carriages
- -Picked up lots of steel and factories burned
- -2,209 people died
- -American Red Cross came about with Clara Barton
Describe the case study Big Thompson
- -July 31, 1976
- -Night before 100th year of Colorado statehood
- -Raining in the mountains, not in valleys so people can't see
- -V shaped valley
- -12 to 14 in of rain in 4 hours
- -Flash flood
- -143 deaths
Describe the case study Cairo, Illinois
- -Between Mississippi and Ohio river
- -2011 getting ready to flood
- -Blew up levee to lead the flood to the farmers land instead of the city
What are the conditions for tornadoes?
- -Collision of air masses
- -High wind shear
- -Intense updraft
When is tornado season?
How do you measure tornadoes and what is it based on?
- -Enhanced Fujita Scale
- -Based on wind speed and damage
What is wind shear?
- -Wind blowing in different directions
- -Generates tornadoes
What lifts things up in a tornado?
What do you do if there is a tornado coming?
- -Get underground
- -Inside first floor bathroom of your house
What is the Coriolis effect?
-Atmospheric circulation combined with rotation of Earth
Describe low pressure and high pressure
- -Low pressure is severe weather
- -High pressure is cooler temperatures and clear skies
- -Cold front means higher pressure
- -Low pressure and warm front is sever weather
What fronts have to meet for a tornado to form?
-Warm and cold
What type of air holds more moisture?
How are severe thunderstorms generated?
-Warm moist air that moves upward, it cools, condenses, and forms cumulonimbus clouds
What are supercells?
- -Really big thunderstorms
- -There's an updraft that rotates upward causing a wall cloud which turn into tornadoes
What is the crest and wavelength?
- -The crest is the top of the wave
- -Wavelengths are the distance between one crest to another
What happens if you have a steep beach?
-You have a plunging breaker (tall waves that surfers go on)
What happens when you have gentle slopes?
-It's called a spilling breaker
What is wave refraction?
Bending of the wave due to something in the way
What is a sea stack, sea arch, and sea cave?
- -A stack of rocks in the sea
- -An arch in the sea
- -A cave in the sea
What is a headland?
- -Something that will eventually erode
- -A piece of land sticking out in the ocean
What is longshore drift?
-Waves coming at an angle and pushes the sand along the shore
What is a spit and how is it created?
-A peninsula of sand caused by longshore drift
What are barrier islands?
- -Large supply of sand
- -Due to longshore drift
What are groins?
-Rocks that stick perpendicular to a shore (used to build beaches/adds sand)
What are breakwaters?
-Parallel to the shore (used to build beaches/sand)
What are jetties?
-Basically the same things as groins but they come in pairs and they keep the bays open
What are seawalls?
A seawall causes beach erosion by focusing energy a its base on the sand
What are the atmospheric layers?
- From bottom to top:
- (Change 6 degree per layer)
Where does extreme weather happen?
-In the troposphere and lowest part of the stratosphere
- -Visible form of energy transfer
- -Caused by electrical imbalance in cloud
What do you do if you see lightning?
- -Go inside
- -Don't use corded phone
- -Get away from trees
- -Stay close to ground and in fetal position
When is hurricane season?
June-November with August-October being the worst
What are the ingredients for a hurricane?
- -Warm water (at least 80 degree F is fuel)
- -High humidity
- -Low pressure
- -Low wind shear
- -Warm moist air rises and condenses
- -Condensing releases heat
- -Starts to create thunderstorms over the oceans
What is the eye, and eye wall of a hurricane?
- The Eye:
- -High pressure
- -Center of it
- -Clear day when eye passes over
- Eye Wall:
- -Low pressure
- -Just to the left of the eye
What is the worst quadrant of a hurricane?
What are storm surges?
- -Low pressure of hurricane acts like a plunger, pulling ocean up
- -High winds push the water, stacking it up
How do you measure hurricanes and what is it based on?
- Saffif-Simpson Hurriane scale
- Based on wind
Describe the case study of hurricane Katrina
- -They predicated it a couple months prior
- -75 miles across from the middle to the East side
- -The "fish bowl" city flooded from being 12 feet under water on both sides to 22 feet
- -85% of people got out
- -80% of New Orleans was flooded
- -Water stayed there for a month
- -Most expensive natural disaster in U.S. history at $125 billion
- -1,600 people died
Describe the case study Tri-State Tornado
- -3.5 hours
- -217 mile track
- -180 mph winds
- -Over 600 dead
What are the conditions for wildfires?
- -Dry conditions
- -Wind drafts(causes fire to spread)
- -Debris flows after
- -35 mph wind
- -Visibility less than 0.25
What is karst topography?
- -Dissolution of rocks
- -Limestone dissolves easily
Describe stalactites and stalagmites
- -On the ceiling
- -On the ground
What is a sinkhole?
-A cavern underground
What is subsidence?
-Removing water from an area that cause ground to fall/sink
What happens to clay when it gets wet?
-It expands and dries as it shrinks
Equations I need to know:
- T=D/R (Time equals distance divided by rate)
- Tsunami is
- Earthquake increase from one magnitude is 32x
What is lava?
-Hot molten rock erupted from a volcano
What is magma?
-Hot fluid below or within the earth's crust
At which tectonic settings would you find the three types of volcanic rocks?
Andesite and Rhyolite at convergent, Basalt at divergent
What is intensity and how do you measure it?
-It is the severity of the shaking and is measured with the Modified Mercalli Intensity Scale
What would you like to do?
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