Hazards Flashcards
Hazards can be categorised into
Magnitude
Frequency
Duration
Spatial concentrations
Speed of onset
Risk
The probability of a hazard occurring and creating loss
The exposure of people to a hazardous event presenting a potential threat to themselves, their possessions and the built environment in which they live
Vulnerability
Risk and ability to cope
HICs may be less vulnerable as they have more money to recover
Hazard
A threat which ahs the potential to cause injury, loss of life, damage to property, socio-economic disruption or environmental degradation. Can be caused by either natural or human processes
Natural hazards
Hazards which occur in the physical environments of the atmosphere, lithosphere, and the hydrosphere
Disaster
Hazardous event that causes unacceptably large numbers of fatalities and/or overwhelming property damage. Occur as a result of a hazard
UN classifies a hazard a disaster when:
>10 people killed
>100 people affected
State of emergency is declared
Request by government for international assistance
Categories of natural hazards
Geophysical - caused by movements of the earth
Atmospheric - weather related
Hydrological - water-related hazards
Factors that influence your perception of a hazard
Previously affected by a disaster - may be more wary next time it happens - takes more precautions
Never affected by a disaster - may be naive to how much the hazard will affect them or perhaps be overly worried
Primary sector worker - industry may be more likely to be affected - crops dying, injuries preventing physical labour, rural land rendered inaccessible
Tertiary sector worker - may be less affected as a lot of money will be focussed on rebuilding the tertiary sector. If can’t go to work likely to still be paid
Highly educated - more likely to know the affects of the disaster
Poorly educated, suspicious of the media - less likely to know how the disaster will impact them, won’t believe new coverage of the event
Integrated risk management
Often used when incorporated identification of the hazard, analysis of the risks, establishing priorities, treating the risk and implementing a risk reduction plan
Prediction
Key is to improve monitoring which means warning can be issued
+
Grindavik - predicted volcano and everyone was evacuated
-
Haiyan - didn’t correctly predict route
Protection
Aim is to protect people, their possessions and the built environment. Usually involves modifications to the built environment
+
Storm surge sea walls in East USA
-
Fukushima nuclear power station - tsunami wall failed
Prevention
For natural hazards it is probably unrealistic although there have been ideas such as cloud seeding in potential tropical storms
+
Otley flood prevention
-
Carlisle flood defence didn’t work
Risk sharing
a community preparedness strategy where the risk of a natural hazard is shared among members, and they collectively invest in mitigation measures to reduce future impacts. This involves pooling resources
+
Emergency shelters in hurricanes
-
Hurricane Katrina
How can we track tropical storms
Computer tracking programmes - forecast paths
Satellite + radar systems - maintain watch on progress
Tracking stations in hurricane hotspots - Miami + Japan
How predictable are tropical storms
Clearly seen, can be tracked by satellite
The specific requirements mean that scientists know when and where they will form
HOWEVER
Each hurricane is unique both in its own structure and dynamics and its meteorological
Small changes in the early development of tropical storms can have massive impacts later on
Storm surges
Pose the greatest threat to life from all hazards created by tropical storms
An abnormal rise of water generated by a storm’s winds. Storm surge can reach heights of 20ft and can span hundreds of miles of coastline
Can result in loss of life, buildings destroyed, beach + dune erosion, and road and bridge damage
Heavy rainfall from tropical storms
Tropical storms often produce widespread torrential rains in excess of 6 inches
May result in destructive floods - major threat for people living inland
Rainfall amounts related to speed and size of the storm
High winds in tropical storms
Tropical storm-force winds are strong enough to be dangerous if caught in them
Hurricane-force winds, 74-150+ mph winds can destroy homes and buildings
Wind force measured by Saffir-Simpson scale
Landslides from tropical storms
Increased flooding may cause landslides in mountainous regions
Can cause the destruction of crops, roads, bridges and villages. Most areas along US coastline prone to hurricanes are not very mountainous. The most susceptible places are central American and NW Pacific
e.g. intense rain from Hurricane Mitch (>4in/hour) caused a massive landslide on a volcano in Honduras
Ground fire
Burns beneath the ground in layers of organic peat
Surface fire
Burns across surface vegetation
Crown fire
Spreads across tree canopies + affects forested areas
BAD
Ladder effect in wildfires
Describes the process of fires spreading from the forest floor to the canopy
Distribution of wildfires
Hot places
Benefits of wildfires
Small regular areas burning can reduce amounts of fuel, lowering the likelihood of large fires
Remove alien plants
Ashes add nutrients (previously locked in other vegetation) to the toil
Controlling insects by killing off older or diseased trees
Human causes of wildfire
Cigarettes
Campfires + barbecues
Fireworks
Arson (biggest cause)
Physical causes of wildfire
Lightning - biggest cause
Volcanic eruptions
Spontaneous heating - occurs when high dry material and no flow of cooling air
El Nino
Drought
Primary effects of wildfire
Smoke
Destruction of property + possessions
Loss of life + injury
Loss of vegetation + crops
Loss of animal habitats
Secondary effects of wildfire
Increased soil erosion as vegetation is no longer there the bind the soil
Loss of jobs + income for agricultural workers who lose crops
Homelessness
Insurance premiums rise
Access to recreational areas is restricted
Health problems from inhalation of smoke
Disaster relief cycle in wildfire
Preparation (making buildings and residents ready) → Mitigation (reducing the potential severity of impact) → Response (dealing with immediate threat) → Reflection → Recovery (healing and regaining control) → Adaptation (making change to meet needs)
Response to wildfires
Fire lines - a break is made in the vegetation to try and prevent the wildfire from spreading
Firefighters spray the fire with water and foam
Spray ahead of wildfires to prevent spreading
Back burning areas ahead of the fire are sprayed to reduce fuel
Air drops - fire retardant dropped on fire
Preparation for wildlife for homes
Have a fire hose
No dense trees near the house
Mowing vegetation 100ft away from house
Burnable materials (e.g. woodpile) kept away from the house
Avoid outdoor burning
El Nino
Happens when weakening trade winds allow the warmer water from the western Pacific to flow toward the east. The clouds and rainstorms associated with warm ocean waters also shift toward the east, leaving drier conditions in Australia.
Tropical thunderstorms are fuelled by hot, humid air over the oceans. The hotter the air, the stronger and bigger the thunderstorms. As the Pacific’s warmest water spreads eastward, the biggest thunderstorms move with it. This increases the intensity and frequency of tropical storms forming over the Pacific.
What makes people vulnerable to wildfires
Geographical positioning - El Nino, Indian Ocean Dipole, high pressure
↑ urban sprawl and population means more people living near forests etc
Drought
Downwind from dry winds
Areas inland with lots of vegetation/type of vegetation
↑ rural populations
Crust
Continental (30-50km)/oceanic crust (5-10km)
Heat from the core
> 5000 C
Primordial heat left from Earth’s formation is trapped
Radiogenic heat produced by radioactive decay
Biological evidence for plate tectonics
Fossils found in areas that weren’t near each other so concluded that they used to be - Pangaea - and that’s why fossil evidence can be found on different continents
Fossil brachiopods found in India are comparable with ones in Australia
Fossilised remains of a plant which existed when coal was being formed have been located only in India and Antarctica
Geological evidence for plate tectonics
South America fits with Africa
Evidence of a late-Carboniferous glaciation deposits found in SA, Antarctica and India, the formation of these cannot be explained by their current position
Rock sequences in northern Scotland closely match formations in eastern Canada and Appalachia
Sea-floor spread - stripes of metals are magnetised according to polarity of earth which flips every 400k years. Evidence of sea floor spread as the magnetic bands are mirrored either side of the mid-Atlantic ridge
Characteristics of young fold mountains
High peaks (>6km), steep slopes, deep valleys
Glaciers
River sources due to snow melt
No volcanoes at destructive but yes at collision
e.g. Himalayas
Collision plate boundary
Convergence of two continental plates
Destructive plate boundary
Convergence of a continental and oceanic plate
Formation of young fold mountains
Two tectonic plates moving towards each other at a destructive plate boundary and there is slab pull. Sediments between the plates are compressed into rock and folded into mountains
Characteristics of rift valleys
Long + narrow with steep sides
Floor is flat or gently sloping
Thick layers of sediment from erosion
Volcanoes
Great Rift Valley - Africa, Mt. Nyiragongo
Formation of rift valleys
Plates move apart on continental areas. Brittle crust fractures as sections move apart. Areas of crust drop down between parallel faults to form the valley.
MARS BAR
Characteristics of ocean ridge
Mid-Atlantic ridge
Volcanic activity occurs
Sea floor spread
Sometimes volcanoes rise above ocean surface e.g. Iceland
Formation of ocean ridges
Plates move apart in oceanic areas
Space between the plates is filled with basaltic lava upwelling
Characteristics of deep sea trenches
Associated with island arcs
Mariana trench - 1100m deep
Formation of deep sea trenches
Oceanic and continental plates meet
Oceanic plate subducts
Characteristics of island arcs
Long, curved chain of island
Marianas islands - Guam
Parallel to trench
Formation of island arcs
Destructive boundary
Oceanic crust subducts which leads to formation of volcanoes which make islands.
Formation of Hot Spots
Concentrated decay in earth’s core will form hotspots
These heat the lower mantle creating localised thermal currents where magma plumes rise vertically.
These plumes occasionally rise within the centre of plates and burn through the lithosphere to create volcanic activity on the surface
As the hotspot remains stationary the movement of overlying plate results in the formation of a chain of active and subsequently extinct volcanoes as the plate moves away from the hot spot e.g. Hawaii
Arguments against hotspots
Bend in Emperor Seamount and Hawaiian ridge but no evidence to suggest that Pacific plate changed direction
Mapping shows Iceland’s hotspot would have been below Greenland but there’s no island chain between Iceland and Greenland - (theory is that there was an old subduction zone which has now disappeared
Too much magma for it to be just melted oceanic crust in Iceland
Causes of earthquakes
Movement of tectonic plates
Building of large reservoirs
Deep mining
Fracking
Focus
Point at which pressure is released within curst
Shallow focus will be felt stronger
Epicentre
Point on earth’s surface immediately above the focus
Primary waves
Hit first
Little impact on people
Secondary waves
Hit seconds after primary
Higher impact as energy moves perpendicular to direction of movement which shakes the earth
Love waves
Slow and large
Twist from side to side and make buildings vulnerable
Travel along surface
Rayleigh waves
Very impactful
Travel along surface
Barrel roll
Richter Scale
Used to find how powerful an earthquake was
Logarithmic scale from one to nine
Mercalli scale
Measures the intensity of an earthquake
12 increasing levels of intensity
Subjective measure
Moment Magnitude Scale
Used by seismologists
Used to compare size of earthquakes where Richter scale (which saturates for earthquakes > 7) isn’t so accurate
Measures energy released by earthquake
Primary impacts of seismic hazards
Ground shaking
Ground rupture - breathing and displacement of the earth’s surface
Secondary impacts of seismic hazards
Liquefaction
Tsunami
Fires - gas lines
Flooding
Landslide/avalanches
Death
Buildings collapsing
Destruction of infrastructure
Liquefaction
Vibrations in saturated soil cause the particles to lose contact with each other and act as a liquid
Soil is unable to support weight and cars can sink into it
High risk on land reclaimed from ocean
Tsunami
Caused by shallow-focus underwater EQs + volcanic eruptions
Have very long wavelength and a low wave height which rapidly increases when it reaches shallow water
Travel at 700km/hour
The wave will wash boats and wooden coastal structures inland, backwash may carry them out to sea
Drowning
Infrastructure washed away
Impacts reach 500-600m inland
Prediction of EQs
Can’t really predict EQs
Attempts to predict EQs
Observing unusual animal behaviour
↑ water level
↑ radon gas concentrations
Foreshocks (can’t tell if they’re foreshocks or just small EQs)
Preparation and protection of EQs - Federal Emergency Management Agency
FEMA aims:
Promotes understanding of EQs + impacts
Work to better identify EQ risk
Improve EQ-resistant design and construction
Preparation and protection of EQs - hazard resistant structures
Concrete counter-weight in top of buildings - Taipei 101
Rubber shock absorbers in the foundations
Older buildings can be retrofitted
Preparation and protection of EQs - education
Individual preparation - securing homes, making ‘emergency kits’
EQ drills at school
Japan has disaster prevention day
US Red Cross - list of supplies for 3-day survival kit
Preparation and protection of EQs - fire protection
Smart meters can cut off gas if an EQ of sufficient magnitude occurs
Preparation and protection of EQs - emergency services
Training on procedure following EQ
Computer programmes which identify which areas need emergency services the most
Preparation and protection of EQs - land use planning
Identifying hazardous areas - e.g. Christchurch + liquefaction - and not building essential infrastructure there
Preparation and protection of EQs - aid
Only focussed on helping days after - no long-term aid
Provide medical services, tents, water purification equipment
Preparation and protection of EQs - tsunami protection
Can’t be entirely predicted but early warning systems through networks of buoys which measure water pressure
Fukushima tsunami wall was ineffective and nuclear plant was damaged - evacuation 20km radius
Active volcano
A volcano that has erupted within recorded history and is currently erupting or showing signs of unrest - Mauna Loa
Dormant volcano
Hasn’t erupted in thousands of years but has the potential to erupt again - Mt. Kilimanjaro
Extinct volcano
Not going to erupt again - Arthur’s Seat
Location of volcanoes
95% occur on fault lines - subduction zones, mid-ocean ridges, rift valleys
5% occur on hotspots
Viscosity of lava
Character of volcanoes is largely controlled by viscosity
High viscosity lavas flow slowly and cover small areas
Low viscosity lavas flow more rapidly and cover thousands of km^2
Low viscosity allows gases to escape easily, whereas gas pressures can build up inside high viscosity lava resulting in violent eruptions
More silica → more viscous
Fissure volcano
Type of eruption, viscosity, acidity, type of rock, character, boundary
Icelandic
Very low
Basic
Basaltic
Effusive - lava flows gently from fissures
Constructive and hotspots
Shield volcano
Type of eruption, viscosity, acidity, type of rock, character, boundary
Hawaiian
Low
Basic
Basaltic
Wide, gently sloping sides and frequent, none-violent eruptions
Constructive and hotspots
Dome volcano
Type of eruption, viscosity, acidity, type of rock, character, boundary
Strombolian
Low - higher than shield
Basic
Basaltic
Explosive but not as strong as others
Destructive
Ash-cinder volcano
Type of eruption, viscosity, acidity, type of rock, character, boundary
Vulcanian
Middling
Acidic
Basaltic/andesitic
More explosive, less frequent
Destructive
Composite volcano
Type of eruption, viscosity, acidity, type of rock, character, boundary
Pelean
High
Acidic
Andesitic/rhyolitic
Steep, conical shape, violent eruptions, pyroclastic flow, lahars, ash clouds
Destructive
Andes
Caldera volcano
Type of eruption, viscosity, acidity, type of rock, character, boundary
Plinian
Very high
Acidic
Rhyolitic
Crater-like depression where magma chamber empties and collapses
Several km in diameter
Super-volcanic eruptions
Destructive - Yellowstone
Volcanic Explosivity Index
Relative measure of the explosiveness of volcanic eruptions
0 = non-explosive
8 = very large
Pyroclastic Flow
Explosive volcanoes
Fast-moving current of hot gas and rock which hugs the ground and travels downhill
Speeds up to 700km/h, 1000C
Doesn’t spread too far
Inhalation of gas causes instant death
Mount Vesuvius - Pompeii
Lava Flow
Both explosive and effusive
Between 1000-2000C
Can easily be avoided by a person on foot
Can’t be stopped or diverted
Often burn down vegetation + structures
Can extend several km if the lava is basaltic
Fast-moving lava engulfed 75% of 3 villages in 2014 Fogo eruption - Cape Verde
Tephra
Explosive
Rock material ejected into the air - fine ash to large volcanic bombs
Hazardous as it can cover agricultural land, destroying crops
Cause airspace to be closed
2010 eruption of Eyjafjallajökull led to cancellation of 100,000 flights
Nuees Ardente
Explosive
Similar to pyroclastic flow but denser and slower
1902 - Mount Peleé on Martinique killed 30,000 people
Ash fallout
Explosive
Ash can rise up and form an eruption column up to 45km
Can be transported by the wind over long distances
Covers all buildings, roads and farms over thousands of kms and major disruption
Poisons water sources
Weight of ash can collapse buildings
Eyjafjallajökull
Volcanic gases
Both
CO, CO2, SO2
Silent and deadly threat to humans. Gases irritate eyes, nose, throat, lungs, and can mix with water vapour to form volcanic fog which can be dangerous to breathe
1986 - 1,200 people were killed when an underwater volcanic explosion let off deadly gases at Lake Nios, Cameroon
Mudlfows/lahars
Explosive
Volcanic mudflows with consistency of wet concrete
Form when ash, rock fragments and mud mix with water (usually snow melt)
Travel up to 50km/h and consume everything in path
1985 - small eruption caused big lahar in Tolima, Guatemala and buried whole town - 25,000 deaths
Acid rain
Both
SO2 combines with water in atmosphere
Pollutes surface water, enhances weathering, and can damage crops
Tonga 2022 - volcano has been releasing gas since eruption
Prevention of volcanoes
Can’t prevent them from exploding
Can prevent building close to volcano - exclusion zone around Soufriere Hills volcano in Montserrat
Monitoring and predicting volcanoes
Locating is straightforward
Harder to predict when but still possible:
- monitoring land swelling
- changes in groundwater levels
- changes in gas emissions (increased sulfur)
- monitoring seismic activity
Preparation for volcanoes
Individuals can make plan to get to closest emergency shelter and make emergency kit
Communities can prepare by risk-sharing and organising search and rescue teams
Mitigation of volcanoes
Engineering lava diversion barriers
Cooling lava flows by spraying water to slow advancing lava - Iceland
Ash collection and removal - clearing ash to prevent roof collapses
Not building in an area susceptible to pyroclastic flow
Channels to direct lahars into river channels - Japan
Adaptation to volcanoes
Strengthen buildings to prevent collapse from ash
Buildings near Eyjafjallajökull are 50% stronger and have slanted roofs
Capitalise on opportunities - farming, tourism - Iceland
