Hazards Flashcards
Event
People unaffected
Hazard
People potentially affected
Disaster
People affected
Physical factors influencing hazards development
An area’s level of development (Haiti v Christchurch), location (due to human), type, frequency, magnitude
Climatic hazards
Cyclones, tornadoes, droughts, floods
What affects climatic hazards
Rainfall intensity and distribution, El Nino, time, proximity to ITCZ, land use and catchment morphology
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
Tectonic and geomorphic hazards
Earthquakes, volcanoes, tsunamis, avalanches, mass movement
Tectonic and geomorphic hazards affected by
Plate boundary, heavy snow/rain, magma type, hills and escarpments, local topography and land use
Hurricanes damage
Strength does not lead to damage as cell size, unreliable forecasting, rain, movement speed and sequencing e.g. Jeanne category 2 in Florida where hazard fatigue
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
Tropical storms where
20 degree to 5 degree latitudes
Multiple hazard zones
High human concentration (coastal and in NEEs), near plate boundaries, high concentration between tropics
Multiple hazard zone examples
Philippines experiences cyclones, earthquakes, floods, tsunamis, volcanoes, 240/km2 population density
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
Risk management cycle
Preparation phase, response phase, recovery phase, mitigation phase. Implemented in Cockermouth after second 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: crust, mantle, core
Mechanical layers
Act physically differently: lithosphere, asthenosphere, outer core, inner core
Crust
Thin outer layer (5-70km). Continental known as sial, thicker, less dense at 2.7gcm-3, granitic. Oceanic known as sima, thinner, denser 2.9 gcm-3, 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
Outer core
Semi liquid, mainly iron, spins with Earth’s rotation to form magnetic field
Inner core
Solid, iron and nickel, 5000 degrees, 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
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 Pacific 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 plate at 9-16 cm/yr. Himalayas from accretionary wedge, Tibetan Plateau, volcanic intrusion, earthquakes, crust 2x average thickness at 75km
Oceanic-oceanic convergent
S American plate moving W from Mid-Atlantic Ridge spread and 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 e.g. 1990s Montserrat
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 e.g. San Francisco
Trench example
San Andreas fault, N American and Pacific 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, Kauai oldest above water
Hot spot/constructive margin vulcanism
Red eruptions, silica poor runny lava so effusive, basalt, no volcanic ash as effusive
Destructive margin vulcanism
Grey eruptions, cooler as friction heat only causes partial melt and silica rich so viscous and explosive, large ash clouds, andesite
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 to form a large gently sloping shield volcano
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
Vulcano Island, 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
Volcanic Explosivity Index
A 1-8 scale describing explosivity, technically not top but 8 supervolcano, based on volume material ejected
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
Lava fountains have drops of lava that solidify
Volcanic ash
From explosions blasting apart rocks, creates sludge, very sharp so respiratory issues, collapse buildings as heavy, block Sun, largest 25km so caught in jet stream and Volcanic Winter
Pyroclastic flow
6-700 degrees gas, rock and ash clouds after ash clouds drop travelling over 200mph as heat ground so remove friction e.g. 1991 Mt Unsen Japan killed 43
Volcanic gas clouds
Landslides release CO2 from bottom of lakes in volcanic vents e.g. 1986, Lake Nios 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 distribution across belts example
2 major belts: circumpacific and alpide
Earthquake distribution across rifts example
East African rift valley
Earthquake distribution across hotspots example
Solomon islands
Earthquake distribution across faults example
N Anatolian fault
Earthquake distribution across conservative boundaries
N American and Pacific moving in same direction, Pacific faster
Earthquake distribution across convergent boundaries
Not on subducting side if destructive, more spread out on continental as more brittle e.g. Indian and Eurasian
Focus
Point energy released from
Epicentre
Point on surface directly above focus
Type of earthquakes at conservative boundaries
Plates slide past each other for shallow focus (more damage) earthquakes e.g. San Andreas fault with Pacific 6mm/yr and N American 2mm/yr plates
Type of earthquakes at continental-oceanic convergent boundaries
Wadati-Benioff zone, up to 600km deep earthquakes e.g. Kuril islands subduction zone
Type of earthquakes at continental-continental convergent boundaries
Crustal thickening and deformation over a large area so a broad zone of shallow earthquakes e.g. 2005 Kashmir earthquake
Type of earthquakes at divergent boundaries
<30km deep shallow earthquakes at a narrow zone close to spreading ridge, low magnitude, extensional faults
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
How to protect from wildfires unnaturally
Resilient landscapes, fire adapted communities, innovative fire management
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
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 scale
1-5 Saffir Simpson Scale off windspeed
