Hazards Flashcards
Event
People unaffected
Hazard
People potentially affected
Disaster
People affected
What influences hazard impact
Development, hazard intensity, distribution, magnitude, incidence
Geophysical hazards
Caused by land processes
Atmospheric hazards
Extreme weather events originating in the atmosphere e.g. tropical storms, heatwaves, wildfires
Hydrological hazards
Water-related e.g. floods, landslides, droughts
El Nino Southern Oscillation
Fluctuates between El Nino (opposite to normal conditions, winds reverse, warm water and low air pressure towards S America increasing rain, high Australian pressure causes drought), neutral, and La Nina (exaggerates normal) every 3-7y. Recently exceptional El Nino events
Hurricanes damage
Strength does not lead to damage as cell size, unreliable forecasting, rain, movement speed and sequencing
Earthquakes damage
Most frequent hazard but massive differences in effects, frequency not increasing but human vulnerability is
Volcanoes damage
Much less significant impact and loss of life than other hazards, affect 95000/yr
Tsunami damage
Impact limited geographically as at the edges of some oceans but 2004 sent waves round world due to Indian Ocean bathymetry and 9.2 earthquake size, 5m waves in India 1700km from epicentre
Multiple hazard zones
High human concentration (coastal and in NEEs), near plate boundaries, high concentration between tropics
What are the responses to hazards
Fatalism, prediction, adaptation, mitigation, management, risk sharing
Physical factors affecting response
Severity, accessibility, hazard type, time, weather, fauna and flora, frequency
Human factors affecting response
Politics, population density, money, accessibility, knowledge, development
Who controls response
Government, academics, insurers, planners, relief agencies, emergency services, communities
Hazard cycle
Hazard, emergency, recovery, reconstruction, disaster free period
Limited response success example
Kashmir Earthquake 2005, Pakistan refused aid from India as at war over area and army slow, US criticised as didn’t raise enough, 80000 deaths as poorly built schools and hospitals. Challenges as war zone, Winter, mountainous
Response success example
Boscastle flood 2004, no casualties as fast response close to RAF station
Matrix risk
Likely impact and probability determine whether red, amber or yellow warning
Hazard management cycle
Preparation phase, response phase, recovery phase, mitigation phase. Implemented preparation in Cockermouth after 2009 flood
Effect of community preparedness and education
Disaster reduction most effective at community level as meets specific local needs, cheaper than emergency relief
Technology in risk preparation
Remote sensing, GIS in plans and hazard maps for reduction, communication, Pacific ocean has well maintained tsunami warning systems, Indian ocean has none as LICs and NEEs but after 2004 USA and Japan installed some
Park response model
1: modify cause and event. 2: hazard event. 3: search, rescue and care. 4: relief and rehabilitation. 5: recovery (improvement)
Compositional layers
Different chemical structure
Mechanical layers
Act physically differently
Crust
Thin outer layer (5-70km). Continental known as sial, thicker, less dense, granitic. Oceanic known as sima, thinner, denser, balsatic
Mantle
Rich in iron and magnesium, mainly peridotite, 2900km
Core
Made of iron and nickel, 3450km
Lithosphere
Solid, divided into 7 large and many small tectonic plates, upper mantle and crust
Asthenosphere
Rocks become plastic as solid from pressure despite temp so flow, peridotite
Outer core
Semi liquid, mainly iron, spins with Earth’s rotation to form magnetic field
Inner core
Solid, iron and nickel, radioactive decay supplies heat, convection currents
Convection currents
Unlikely to move plates as not large enough and 2/3 surface moves faster than mantle
Ridge push (gravitational sliding)
Mantle material pushed into a plate gap, forcing them apart and up, gravity pushes down, allows sea floor spreading
Slab pull
Drives convection currents. Newly formed oceanic lithosphere at mid ocean ridges less dense than asthenosphere but denser with age so subducted on collision with continental plate
Constructive/divergent boundary
Mid Atlantic Ridge between Eurasian and North American plates. Gravitational sliding, earthquakes and volcanoes
Triple Junction: continental rifting
East African rift valley due to S extension of Arabian and African plate divergence and rifting from mantle plume: African plate will split to Nubian and Somalian. Continental filled with oceanic, earthquakes, and volcanoes
Oceanic-continental convergence
Andes due to collision of S American and Nazca plate. Mountains (obduction forms an accretionary wedge), volcanoes (andesitic magma from subduction liberating seawater locked in crust), earthquakes (Benioff zone), Atacama trench
Continental-continental convergence
Himalayas due to collision of Indian and Eurasian plates and subduction of Tethys ocean floor plate dragging Indian. Himalayas from accretionary wedge, Tibetan Plateau, volcanic intrusion, earthquakes, crust 2x average thickness at 75km
Oceanic-oceanic convergent
S American plate meets warmer Caribbean, less dense so subducts forming Puerto Rico Trench and obduction has accretionary wedges forming Caribbean islands form a volcanic island arc parallel to the trench, earthquakes, andesitic magma eruptions
Conservative
San Andreas fault between N American and Pacific plates, 1300km long, right lateral strike slip fault as Pacific moving NW faster, shallow focus earthquakes
Trench example
Atacama, S American and Nazca plates
Volcanic arc example
Andes, Nazca and S American plates
Island arc example
Caribbean islands, S American and Caribbean plates
Fold mountains example
Himalayas, Indian and Eurasian plates
Rift valley example
East African rift valley, African plate
Mid ocean ridge example
Mid Atlantic Ridge, N American and Eurasian plates
Mantle plumes
Hot molten rock plumes from the mantle-core boundary to the Moho e.g. Hawaii
Icelandic volcano
Molten balsatic lava effusions flow from long parallel fissures
Icelandic volcano example
Skaftareldar, Iceland
Hawaiian volcano
Fluid lava flows from a volcano’s summit and radial fissures
Hawaiian volcano example
Mauna Kea, Hawaii
Strombolian volcano
Moderate bursts of expanding gases eject lava clots in nearly continuous small eruptions
Strombolian volcano example
Stromboli volcano, Italy
Vulcanian volcano
Moderate gas explosion laden with volcanic ash to form clouds
Vulcanian volcano example
Gran Cratere, Italy
Pelean volcano
Explosive outbursts generate dangerous pyroclastic flows
Pelean volcano example
Mount Pelee, Caribbean
Plinian volcano
Very violent as gases boil out of magma, caving it out to form ash clouds causing static electricity lightning
Plinian volcano example
Mount Vesuvius, Italy
Phreatic eruptions
Steam driven eruptions from when water is heated by volcanic activity, very dangerous and hard to predict
Phreatic eruption example
Mt Unzen, Japan, 1991
Volcano spatial distribution
Constructive, hotspots (silica poor red eruptions) and destructive (silica rich seabed grey)
Volcano magnitude: Volcanic Explosivity Index
A 1-8 scale describing explosivity, technically not top but 8 supervolcano, based on volume material ejected
Volcano frequency
50-60/month
Volcano regularity
Type at each boundary regular
Volcano predictability
Long-term with regularity and short-term with warning signs
Lava flows
High viscosity slow e.g. 2002 Mt Nyiragongo exploded a petrol station, low viscosity follow terrain e.g. 1973 Heinaey Iceland threatened harbour so sprayed saltwater to divert
Volcanic bombs (tephra)
Lava fountains have drops of lava that solidify
Volcanic ash (tephra)
From explosions blasting apart rocks, creates sludge, very sharp so respiratory issues, collapse buildings as heavy, block Sun, Volcanic Winter
Pyroclastic flow (nuee ardente)
6-700 degrees gas and tephra travelling over 200mph as heat ground so remove friction e.g. 3km after Merapi
Volcanic gas clouds
Landslides release CO2 from bottom of lakes in volcanic vents e.g. 1986, Lake Nyos suffocated everyone in valley village
Lahars
Volcanic mudflow from eruptions melting snow and mixing with ash e.g. 1985 Nevado del Ruiz, Colombia, eruption caused a huge rainstorm so lahar into Armero town, killed 23000/29000
Jokullhaup
Glacial outburst flood from eruption melting bottom of glacier, massive e.g. Eyjafjallajokull, 2010, peak flow 2-3000 m3/s
Supervolcano caldera formation
Vents around edges cause caldera collapse e.g. Lake Taupo, New Zealand
Earthquake
A sudden, violent ground shaking of the ground caused by sudden energy release in the Earth’s lithosphere that creates seismic waves
Why do earthquakes occur
Lithosphere rigid and brittle so can fracture
Earthquake spatial distribution
2 major belts: circumpacific and alpide, along all boundaries and hotspots e.g. Solomon islands
Earthquake frequency
Occur every day at boundaries
Earthquake regularity
No pattern and random so irregular
Earthquake predictability
Nearly impossible, some microquake indication, can’t predict magnitude
Shockwaves
Energy released from the sudden jolt that vibrates through the ground
Tsunamis
Water displaced from underwater plate movement
Liquefaction
Soil saturated and vibrations weaken it so subside when a large weight on it
Landslides and avalanches
Displace large volumes material
Focus
Point energy released from
Epicentre
Point on surface directly above focus
Body waves
Primary and secondary waves
Primary
Compressional
Secondary
Transverse waves do more damage as lateral movement
How body waves inform Earth’s structure
P waves travel through liquid and solid but different travel speeds and refraction, S wave shadow as can’t travel through liquid core
Surface waves
Rayleigh (up and down) and Love (side to side) waves after body
How are earthquakes measured
Seismometers, use vibrations if old fashioned and electromagnets if modern
Triangulation
Locates an earthquake using 3 stations as we know how fast P+S waves travel (P faster) so time between indicates distance but not direction so must triangulate
Moment Magnitude Scale
Logarithmic, measures energy release, 1 increase x32 energy
Modified Mercalli Scale
Qualitative, measures intensity, subjective, accounts for focus depths, measured with visible aspects, I to XII
Earthquake proofing
Building shape, automatic shutters and shut off, secure heavy objects, open areas for safe evacuations, good road access, earthquake safety training, cross bracing, sheer walls (steel bars), Taipei 101 66 tonne mass dampener
Wildfire
A large uncontrolled destructive fire that burns quickly over woodland/grassland
Ground fire
Ground burns slowly with no flame and little smoke
Surface fire
Leaf litter and low lying plants burn faster as more O2 available
Crown fire
Moves rapidly and intensely through canopy
Conditions needed for wildfires
Vegetation type, fuel characteristics, climate, fire behaviour (creeping or running)
Wildfire impacts
Some plants need fire to germinate, affects forest management, fire removes soil OM
Responses to wildfires
Spray water on house roofs to prevent burning, train civilians as auxiliary firefighters, controlled burning of firebreaks, lightning detection systems, land use planning ensures houses 30m from forest and in low density clusters
Megafires
Fires over 1000 acres, predicted to be 50% more by 2100
What % of new USA homes in flammable areas
60%
How to protect from wildfires naturally
Natural patchwork forests of older trees
LA fires damage
Mostly in Eastern Palisades, some fire resistant houses survived
LA fires causes
Santa Ana winds, Hollywood hill camper barbecues, prosecuted an electrics company for sparks
Amazon fires
2019, unusual as often too moist
Hurricanes
Atlantic, almost none in S
Typhoons
W Pacific, highest frequency
Cyclones
Indian Ocean and Australia
Where and when do tropical storms occur
Coasts, travel in trade wind direction, occur late Summer to Autumn, 5-30 latitudes but higher off N America
Where don’t tropical storms occur
Not in SE Pacific, S Atlantic, and equator
Tropical storm magnitude
1-5 Saffir Simpson Scale off windspeed
Tropical storm frequency
N hemisphere: Jun-Nov, S hemisphere: Nov-Apr, 2x 4-5 in 30y
Tropical storm regularity
Irregular as same areas but not route as depends on storm and climactic conditions
Tropical storm predictability
Of general route as satellite tracking of cloud formation and movement
What windspeeds
> 120 km/hr winds
What diameter
600km
What pressure
950 to 870mb
Formation conditions
Ocean water >27C (latent heat release), late Summer allows time to heat through, unstable atmosphere
Tropical disturbance
Associated with an easterly wave in the upper wind
Tropical depression
At least one closed isobar (band of atmospheric pressure)
Tropical storms
Sustained winds >37mph
Hurricane/ typhoon/ cyclone
Sustained winds >120 km/h
Hurricane formation
Warm air rises rapidly in low pressure conditions after evaporation, causing low pressure, self-propagating system, Coriolis effect causes air to spin around an eye, adiabatic cooling after air rises forms bands of cumulonimbus cloud, heat given off allows more evaporation
Frequency and strength correlation
If stronger, less frequent
Tropical storm trends in America
August: further out in Atlantic forming. September: widest area covered, forming in Gulf of Mexico. October: less area but further inland
Hazards
Wind, heavy rain, landslides, tornadoes, floods, storm surge (low pressure domes ocean surface)
What is needed to be a MHZ
Tectonic hazards, climactic hazards, vulnerable population
How are MHZs identified
2010 WB and Colombia project to allow planning (not if different priorities)
Where is the highest economic and mortality risk MHZ
Taiwan
What is the only HIC in the top ten most economically and mortality affected MHZs
Japan
