Hazards Flashcards
Define hazard
A natural hazard is a perceived natural/geophysical event that has the potential to threaten both life and property
What are tectonic hazards?
Large scale processes associated with the movement of tectonic plates
Volcanic: pyroclastic flows, ash fallout, tephra, lava flows
Seismic: Ground shaking, liquefaction, tsunami
Hydrological hazards?
glacial flooding, river flooding, storm surge and coastal flooding
Atmospheric hazards?
Drought, tropical storm, acid rain
Geomorphic hazards?
Landslides, mudflows
Biohazards?
Wild fires
How can impacts of hazards be categorised?
Social, political, environmental, economic, demographic, primary, secondary, short term, long term (temporal scale), local, national, regional, global (spatial scale).
Define disaster
The realisation of a hazard when it causes a significant impact on a vulnerable population. The hazard exceeds the capacity and resilience level of the population.
Define vulnerability?
The risk of exposure to hazards, combined with an inability to cope with them.
How does a hazard become a disaster?
Hazard event + vulnerable population
UN definition of a disaster?
Report of 10+ people killed
Report of 100+ people affected
Declaration of a state emergency by the relevant government
Request by national government for international assistance
Factors encouraging a hazard to develop into a disaster?
Magnitude Frequency Duration Areal extent Spatial concentration Speed of onset Regularity
How does frequency affect a disaster?
Usually an inverse relationship between frequency and magnitude
Areas experiencing lots of disasters often have lots of adaption and mitigation measures in place.
What is areal extent?
The size of the area covered by the hazard eg ash clouds can cover a large part of the atmosphere.
What human factors affect whether a hazard turns into a disaster or not?
Economic factors, social factors, political factors, geographical factors, technological factors (building design), and environmental factors.
Define risk
The probability of a hazard ocurring and creating a lossof lives and/or livelihoods.
Define resilience
The degree to which a population or environment can absorb a hazardous event and yet remain within the same state of organisation i.e. its ability to cope with stress and recover.
What is economic resilience?
Diversity of economic income/activity - not reliant on one sector
savings for recovery - on national scale and individual scale
Access to aid and trade
Insurance (individual scale) companies
Social resilience?
Community preparedness
Community relationships and networks
Why do people live in hazardous locations?
Rewards outweigh risks e.g. fertile soils have high agricultural potential.
Cultural connections to landscape place
Risks are effectively mitigated by hazard management.
Lower income communities may have no alternative.
Perception of hazard
Political factors eg refugees forces to settle
Lack of awareness
Define fatalism? hazard perception
View that people cannot shape the out come, nothing can be done
Define adjustment/adaption? hazard perception
People see that they can prepare for, and therefre survive the events by prediction, prevention and/or protection, depending on the economic and technological circumstances of the area in question.
Define fear? hazard perception
The perception of the hazard is such that people feel so vulnerable to an event that they’re no longer able to face living in the area and move away to regions to be unaffected by the hazard.
Reasons for differences in hazard perception?
Socio-economic status - have the money to prepare
Occupation/employment status-stable employment so may avoid risks of losing job if move away
Level of investment in risk awareness programmes - aware so know what to expect
Level of education - adjustment as know how to adapt
Religion/cultural - may not want to move away due to cultural connection, family
Family/Marital status
Values/expectations/personality
Define mitigation
The reduction in the amount and scale of threat and damage caused by a hazardous event
Define integrated risk management
the process of considering the social, economic and political factors involved in risk analysis, determining the ‘acceptibility’ of damage/disruptions; deciding on the action to be taken to minimise damage/disruption.
Define risk sharing
Pre-arranged measures that aim to reduce the loss of life and property damage through public education and awareness programmmes, evacuation procedures, the provision of emergency medical, food and shelter supplies, and the taking out of insurance.
What’re the stages of integrated risk management?
Establishing the context Risk identification Risk analysis Risk evaluation Risk treatment
What is the disaster response curve?
Shows how quality of life detereorates after a disaster, before improving again. Stage 1 is the disaster itself. Stage 2 is the use of vulnerability strategies. At stage 3, search and rescue continues and the quaity of life begins to improve again. STage 4 involves relief and rehab with the potential of outside help to modify the loss eg temporary housing. Stage 5 includes restoration of normality (reconstruction). After, quality of life can improve above that of pre-disaster, as buildings are reconstructed and mitigation strategies implemented.
Pre disaster - relief - rehabilitation - reconstruction
What is the hazard management cycle?
Pre-disaster (risk assessment, mitigation/prevention, preparedness
Response (warning/evacuation, saving people, immediate assistance, assessing damage)
Post-disaster (ongoing assistance, restoration of infrastructural services, reconstruction, economic and social recovery, ongoing development activities, risk assessment/mitigation/prevention.
Four stages: mitigation, preparedness, response and recovery.
What is fire?
The rapid combustion of oxygen with carbon, hydrogen and other organic material in a reaction producing flame, heat and light.
What are the stages of a wildfire?
Preignition
- pre-heating: fuel drives out due to nearby flames or hot weather
-pyrolysis: wood breaks down chemically, releasing gases, oils etc. Materials are now ready for ignition eg by lighting, electrical wires
Flaming combustion: burning gases = fast, hot fire. Wood cracks, releasing more gases, resins, oils, which are then ignited.
Glowing combustion: fire consumes wood itself = slower, cooler fire.
How does fire behaviour effect the nature of fires?
Crown fire
Surface fire
Ground fire
How does fuel characteristics affect the nature of fires?
Quantity of fuel Size and distribution of fuel elements Energy content of fuel Content of resins, oils, waxes Moisture content
How does climate affect the nature of fires?
Drought/dry weather allows pre-heating
Low humidity = dryer conditions
Semi arid climate = enough precip for vegetation to grow to provide fuel, yet with a dry season to promote ignition.
Foehn winds: cool air rises over relief and heats up as it sinks on the leeward side. Warm air drives fires.
Define convection column
The rising column of gases, smoke, fly ash, particulates, and other debris produced by a fire - can form pyrocumulus clouds.
What is a fire tornado?
Roaring spouts of flames shooting 100 foot into the sky. Forms when a fire heats the air above it, and pulls in cool air at the base, creating a self-sustaining vortex. The vortex also sucks up combustable gases.
What affect do wind speeds have on wildfires?
Light winds: vertical convection column, slow speed
Strong winds: fires move fast, spreads quickly, creates additional hazards. Convection column, firebrands (burning embers, spread randomly) and ‘firenados’.
Very strong winds: fire moves fast. Fire front advances very quickly but not convection column.
How does relief affect wildfires?
If the fire is spreading uphill, there is limited pre-warming of downhill vegetation and so the fire slows down.
If wind is driving the fire uphill, convectuve currents drive the fire uphill which pre-warms and dries out the vegetation.
What areas have the highest fire counts?
Eastern South America
Southern Africa
Northern Australia
Physical causes and exacerbating factors of wildfires?
- dry terrain
- extreme heat
- lightning
- hot volcanic lava
- earthquakes
- drought/little rain
- flammable resin to benefit plants
Human causes and exacerbating factors of wildfires?
Arson Camp fire carelessness Electricity lines/power lines Railways Mis-managed forests Slash and burn agriculture
Short term individual responses to wildfires?
Fill as many containers with water
Place lawn sprinklers in accessible places
Place a ladder against the wall of the house
Turn on as many lights in the house as possible to increase house visibility through smoke.
Short term professional responses to wildfires?
Emergency response eg firefighters, medical services, search and rescue
Creating fire lines
Planes and helicopters - contains water and chemical slurry to smother the flames and fertiliser to protect trees.
4 ways of managing wildfires?
Mitigation
Preparedness
Prevention
Adaption
Give examples of some wildfire responses and managemnet?
Suppress all fires Controlled burning Hazard-resistant design for buildings Notice boards to warn tourists Land-use planning Insurance Infrared remote sensing Weather monitors 30m setback from any forested areas.
Define insolation
Incoming solar radiation that varies significantly on earth.
Define differential heating
Different latitudes recieve different amounts of heat energy.
Define tropical storm
An intense, circular, low pressure weather system that develops over Tropical Oceans, is associated with high winds (120 km/hour +), and heavy rainfall and represents a severe hazard.
India = cyclone
North Atlantic = hurricane
South East Asia = typhoon
Factors affecting the development of a tropical storm?
Oceans and high temperature - form over oceans with a temperature of 26 degrees celsius and above.
Atmospheric instability - forms in instable regions where warm air is being forced to rise eg the ITCZ
Rotation of the earth - explains why tropical storms do not usually form in the region between 5 degrees north and 5 degrees south.
Uniform wind direction at all levels: vertical development would be ‘sheared off’ by multidirectional winds.
60m deep heat.
What causes a tropical storm to rotate?
The coriolis effect
What is the eye wall?
Dense wall or ring of thunderstorms and high winds surrounding the eye
What is the eye?
A column of dry, sinking air at the centre of a storm 30-60km.
What’re spiral rainbands?
Curved bands of clouds and storms that spiral around the centre of the storm. Can extend for hundreds of miles.
What’re towering colonimbus clouds?
Huge thunderclouds associated with heavy rain, lightning, hail and produced by condensation of warm, moist air.
What hazards are associated with tropical storms?
Strong winds
Storm surges
Coastal and river flooding
Landslides
Key facts about the character of Hurricane Maria?
2017 Category 4 155mph sustained wind speed 1.8-2.7m storm surge 96.5cm of rainfall in one storm
Where was Hurricane Maria?
Puerto Rico
Background of Puerto Rico (area hit by Hurricane Maria)
Had been facing a recession for over a decade before the hurricane hit.
Almost half of its residents are below the poverty line
Unemployment rate more than double the national level
When was the last category 4 hurricane to hit puerto rico?
85 years before
What are some excarerbating factors of hurricane maria?
Damage from category 5 hurricane Irma just two weeks before: crippling the electrical grid and leaving 3.4 million residents without electricity. Less than one percent of homeowners had flood insurance.
Social impacts of Hurricane Maria?
Poorest residents were disproportionately affected as they live in hard to reach areas near the mountains, so can expect to be the last group to regain access to water and electricity
Pshychological impacts of the storm
Took nearly 5 weeks for the first public schools to begin opening again after the storm
6 months after the storm many were still without power - Puerto Rico Electrical Power Authority filed for bankrupcy.
How many direct deaths were there from hurricane maria?
65
How many indirect deaths were there from Hurricane Maria?
2975
How many school students were affected by Irma and Maria?
350000
Economic impacts of Hurricane Maria?
£73.4 billion in damages
80% of the crop value wiped out
1/3 workers are employed in small to medium sized businesses and farms were especially hit - 90% drop in customers over the prior year.
How much money from damage did Maria cost to Puerto Rico?
$90 billion (third costliest storm in US history)
What percentage of Puerto Rico’s crop value was wiped out from the storm?
80%
Represents £607 million loss in agricultural yeilds
Environmental impacts of Maria?
30% of tress estimated to have been destroyed (palm trees were more withstanding so risk that these might take over the landscape
Increased nitrate in the water -n algal blooms and nausea
What percentage of trees were destroyed from Maria?
30%
Preparation for Maria?
NHC monitored the storm
Data from hurricane hunters and dropsonde was shared
FEMA was unprepared, not enough water and supplies for a didaster this big - their warehouse had been emtied two weeks prior due to respending to another storm
NHC issued a warning
Prior to the landfall shelters were set up and evacuation orders given
How were FEMA unprepared for Maria?
FEMA was unprepared, not enough water and supplies for a didaster this big - their warehouse had been emtied two weeks prior due to respending to another storm
Relief in response to Hurricane Maria?
5000 tarps delivered 9 days after the storm (thousands more were needed)
10 000 federal defence staff (half were unqualified)
World Central Kitchen delivered 25 000 meals
Mercy Corps distributed nearly $300 000 in emergency cash
Rehabilitation after Hurricane Maria?
FEMA can provide up to $33300 in financial assisstance , only about half who have applied for this housing assistance have recieved it
FEMA has provided around $3000 in individual housng assisstance
Mercy Corps distributed 5000 solar lanterns and 2500 water filters
Why was it hard for residents in Puerto Rico to get financial assistance under FEMA’s households programme?
Mainly because they lack the property records required by the agency to receive aid
Reconstruction after Hurricane Maria?
Today the island is back up for business
Residents have jumpstarted their livelihoods with training and supplies from Mercy Corps, which has restored incomes and boosted the economy.
Most houses only had temporary fixes and blue tarps for roofs.
Issues with power and aid after Storm Maria?
Two months after the storm, 60% were still without power and around 20% without water - slow recovery
Key facts about the characteristics of Hurricane Harvey?
2017
Category 4
132 mph winds
27 trillion gallons
Where did Hurricane Harvey hit?
Texas, USA
Background on the location of Hurricane Harvey?
Houston is the most populous city in Texas
Facts about the rainfall association with Harvey?
Brought a years worth of rainfall in less than a week, overfilled two flood control reservoirs. Broken the record for the most rainfall in any tropical system.
Most significant rainfall event since 1880s.
Exacerbating factors of Hurricane Harvey?
Little thought to sustainable urban design during oil boom
Desire to live alongside water
Highly urbanised areas
Some municipalities built on reclaimed marshes, swamps etc
Flatness of local terrain and proximinty to the Bay and Gulf
Social impacts of hurricane Harvey?
135 000 homes destroyed
1 million cars wrecked
Lots of schools remained closed more than a month into the school year
300 000 people left without electricity
Deaths from Harvey?
88
How many homes destroyed from Harvey?
135 000
Economic impacts of hurricane Harvey?
$125 billion cost from damage
25% of oil and gas production shut down, leading to an increase in price, returned to normal after 10 days.
Environmental impacts of Hurricane Harvey?
Clearing up the rubbish adds to an estimated 8 billion cubic yards of rubbish in Houston alone
Human carcinogens released into waterways
Preparation for Hurricane Harvey?
NHC monitored the storm and data from hurricane hunters and dropsonde was shared
Chemical plants shut down ahead of the storm, along with ocean ports
Fire department preposistioned rescue resources and rescue boats near areas known for flooding
Fire units relocated
Relief for Hurricane Harvey?
10 000 rescue missions
World vision engaged with 60 church partners to mobilize resources eg tents, school supplies, sleeping bags
Relief for Hurricane Harvey?
10 000 rescue missions
World vision engaged with 60 church partners to mobilize resources eg tents, school supplies, sleeping bags
30 000 federal defence staff
Coast Guard deployed 50 aircraft, rescuing 11 000 people
FEMA assigned 28 urban search and rescue teams, which rescued 6500 people
FEMA supplied 3 million meals and $186 million in public assistance and deployed teams of specialists
Rehabilitation after Hurricane Harvey?
Rubbish clearence was priority
Recovered slowed due to diverted funds following Irma and Maria
IN 11 months after, provided emergency relief supplies for 246000 people.
Reconstruction after Hurricane Harvey?
13 million cubic yards of debris
Disparities in ethnicity with building, and 50% of lower income residents weren’t getting the help they needed
In the poorest communities, some residents are still living with relatives or friends because their homes remain under repair. Others are living in flood damaged houses.
What hazards are associated with tropical storms?
Strong winds
Storm surges
Coastal and river flooding
Landslides
What is the Saffir Simpson scale?
Standardised scale to measure the magnitude of tropical storms
5 categories
Now only includes windspeeds
Not used all over the world
Doesn’t discuss other factors. Difficult to extrapolate from wind.
Define frequency?
How often storms occur
Define regularity?
Are the tropical storms evenly spread? Fixed intervals? Patterns?
Environmental statistics from the Australian Wildfires?
One billion animals killed
186 000km*2 vegetation burnt
Emitted over 300 million tonnes of carbon dioxide
Economic statistics from the Australian Wildfires?
5900 buildings destroyed
Causes of the Australian wildfires?
Less than 10% of Australian bushfires are deliberate
Main causes:
- lightning strikes
- Carelessness: outdoor BBQs
Exacerbating factors for the Australian wild fires?
Drought: Several areas were categories as ‘Lowest on Record’. Set of drought conditions. In these periods winds reveresed so blow dry winds
Population pressure and fire management practices:
Rose from 14 million to 25 million in 40 years
Climate change and political attitudes:
Melbournes maximum daily temperatures are expected to rise by 1.6 degrees celcius by 2030. Days where temperature exceed 35 degrees celcius will increase from 8.3 to 20.4 days by 2050.
Future implications of the Australian Wildfires?
Earlier ‘stay at home’ campaigns is now high risk as fires are not minor.
in 2011, 60% of people died within 100m of their home
- Now a need for better advice
Fire Authority tell communities whether it is safer for them to go than stay
Relocate people either to towns or fire refugees. Those who stay at home to defend shouldn’t have children present.
Bushfires warnings aim to save lives.
Prediction of tropical storms?
- Satellites: Hurrican hunters, plane ejects a dropsonde that relays information about air temperature, humidity and wind speed/direction.
- GOES-M used to take photos every 5 minutes
What is the hurricane cone of uncertainty?
Represents the probably track of the centre of the hurricane. The cone represents the uncertainty in the forecast of the stroms centre, not necessarily the area that will experience impacts.
National Hurricane Centre issues 120 hour, 96 hour, up to 12 hour forecasts.
How can storm mapping technologies be used?
Can map historical storm tracks: NOAA satellite tracking maps
Cone of uncertainty
Sea surface temperatures
Strike density
Extent of storm surge
Evacuation routes
Use of mapping after storms for disaster relief.
What are the limitations of storm mapping?
Anomalies in patterns (element of uncertainty)
Post-tropical strom technologies rely on cell service, electricity supply/ smartphone ownership.
Up to date maps
Require time/money for responses e.g. evacuations
People may become complacent if they think storm mapping is acccuarte enough so think they won’t be affected.
Types of mitigation for tropical storms?
Structural intervention, disaster aid and insurance cover.
Structural intervention: soft engineering schemes eg planting trees and building up beaches. hard engineering eg constructing sea walls.
Define crustal evolution.
How the earth’s crust has been formed, destroyed and remade during the planets history.
Define plate tectonics
A scientific theory that explains how major landforms are created as a result of Earth’s subterranean movements.
Describe the structure of the earth’s crust from the top down.
Continental or oceanic crust
Moho discontinuity-boundary between crust and mantle
Lithosphere-crust and rigid upper mantle
Mantle- rigid, semi molten then rigid - 83% of earth’s volume
Asthenosphere-part of mantle where heated rock flows
Outer core-liquid iron, dense, generate a magnetic field
Inner core: solid, nickle and iron, very hot, densest.
How do we know about the interior of the earth?
Comes from measuring seismic waves from earthquakes. As they pass trough the earth they are refracted or bent. The speed of seismic waves depends on density, we can use time-travel of seismic waves to map changes in density with depth.
Describe the properties of continental crust
30-70km
Over 1500 million years
Density = 2.6 (lighter)
Mainly granite, silicon, aluminium and oxygen (SIAL)
Describe the properties of oceanic crust
6-10km
Less than 200 million years
Density = 3.0
Mainly basalt, silicon, magnesium and oxygen (SIMA)
What was Wegener’s plate tectonic theory? (first theory)
16th century - continental fit
1800s - similarities in plant fossils and mountain ranges across continents. Also, mismatch between latitude and sedimentary rock types eg coal in UK and Antarctica.
1912 - continental drift theory published
- 300 mya Pangaea split into Laurasia and Gandwanaland.
- Further drift = todays continent
His theory was rejected (but is correct)
What was Holmes plate tectonic theory? (second theory)
Proposed that continets move because they are carried by the mantle and the mantle moves because of convection currents within it.
How do convection currents within the mantle form?
Radioactive decay of some elements in the mantle and core eg uranium.
When lower parts of the asthenosphere heat up they become less dense and slowly rise.
As they move up towards the top of the asthenosphere, they cool down, become more dense and slowly sink
These circular motions are called convection currents
These currents create drag on the base of the tectonic plate and causes them to move
What is Sea Floor Spreading? (Key theory)
New igneous rock is continuously formed at mid ocean ridges causing the sea floor to widen and driving the movement of continents at the edge of the ocean
Slab pull and ridge push? (Key theory)
Lithosphere plays a more active role
Rising magma pushes land upwards and outwards creating ridges (ridge push)
As lithosphere cools, it becomes more dense, and is pulled away from the ridge under gravity (slab pull)
What are the fundamentals of plate boundaries?
Oceanic crust is denser so sinks beneath continental crust
Continental crust is permenent but oceanic crust is constantly being formed
Some plates eg Eurasian consist of continental and oceanic
Plates cannot overlap
When new crust is being formed in one place, old oceanic crust must be being destroyed in another (or continental being buckled up to form fold mountains)
Describe constructive - oceanic oceanic
Eg Iceland
Processes: crustal diversion, seafloor spreading, ridge push, gravitational sliding, tensional stress, fracturing/fissuring, rising magma, seismicity
Landforms: mid-ocean ridges, central rift valley, shield volcanoes, submarine volcanoes
Type of lava: basaltic (runny)
Type of eruption: fissure eruptions, gentle eruptions
Constructive - cotinental coninental
E. African Rift Valley
Processes: crustal divergence, crustal uplift, rising magma, fracturing, rifting, volcanism, seismicity
Landforms: rift valley, fissures, sheild volcanoes, strato volcanoes
Type of lava: basaltic (runny) from shield volcanoes
andesitic (thicker more gaseous) from strato volacnoes
Hazards: lava, tephra, pyroclastic flows, gases, earthquakes
Destructive - oceanic continental
South America Andes
Processes: subduction, crust melting, rising magma
Landforms: strato volcanoes, fold mountains from continental crust buckling, trench formed by warping ofplates
Type of lava: andesitic (oceanic crust partially melts and rises as less dense
Hazards: earthquakes, lava flows (pyroclastic), ash, tephra
Nature of eruptions: explosive
Destructive - oceanic oceanic
Mariana Island
Processes: subduction, trenching, seismicity, volcanism, melting
Landforms: trenches, stratovolcanoes, underwater eruptions produce Island Arc (curving chain of volcanic islands), submarine volcanoes due to rising magma from the Benioff Zone, no fold mountains
Type of lava: Andesitic
Hazards: explosive, pyroclastic flows, ash, tephra, tsunamis
Destructive - continental continental
Himalayas Processes: folding, deformed due to pressure so continental crust buckles to form fold mountains, faulting. no volcanic activity, seismicity , material is forced down into deep mountain roots Landforms: fold mountains Hazards: earthquakes and landslides Lava: none
Conservative plate boundary
San Andreas
Landforms: the fault itself, offset creeks
Processes: plates move alongside each other (opposite or same direction), friction between
Hazards: earthquakes
What are hot spots?
A small area of crust where an unusually high heat flow is associated with volcanic activity.
The plume of plastic rock from the asthenosphere pushes upwards, forming convection currents, pressure drops and the plastic rock becomes molten, melting and pushing through the crust above. As the plate moves over this hot spot, the upwelling lava creates a steady succession of new volcanoes that migrate along the plate. The plume melts the plates above so the thickness of the crust is smaller.
What is basaltic lava?
Less gassy, runny and the least explosive
What is andesitic lava?
Between basaltic and rhyolitic
What is rhyolitic lava?
High gas content, (less hot), thick (very viscous). It is the most explosive because it boils water, and water vapour gets trapped within in, leading to huge gaseous explosions.
Lava flows? primary
Explosions, asphyxiation due to accompanying toxic gases, coll[ase of an active lava delta that forms when lava enters a body of water
Can bury homes and agricultural land under tens of metres of hardened black rock.
Threat to land and property
If it enters a body of water or water enters a lava tube, the water may boil violently and cause an explosive shower of molten spatter over a wide area
Methane gas can explode when heated
Can collapse and form fast-moving pyroclastic flows
Plate boundary determines type of lava
Pyroclastic flows? (nuess ardentes) primary
Move at very high speeds- typically greater than 80km/h.
Extreme temperature of rock, generally between 200 and 700 degrees celsius can ignite fires
Destroy buildings and land
Death due to inhalation of ash and gas as well as burns
Lateral bursts can occur when the summit crater is blocked and the magma explodes through weaknesses
Tephra? primary
Rock fragments that are ejected during volcanic eruptions that range in size from particles less than 2mm in diameter to fragments over 1m in diameter.
Poisonous gas emissions? primary
Volcanic gases: Carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine. Carbon dioxide from underground volcanic chimneys is dissolved and concentrated at the bottom of the lake. An earthquake triggers a landslide which disrupts the lake water layers. The deep water rises to the surface and carbon dioxide bursts out. Heavier than air, carbon dioxide flows down the sides of the volcano and into the valleys.
Lahars/mudflows? secondary
Lahars are “mudflows”, mixtures of volcanic ash, blocks and water, formed on volcanoes.
Risk of crush injuries, drowning or asphyxiation
Cause destruction of buildings, installations and vegetation caught in their path.
Picks up boulders and erodes river banks
Properties between thick water and wet concrete.
Can remove anything in their path like bridges, highways and buildings.
Debris avalanche? secondary
Hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys.
Flooding (secondary)
Volcanoes in cold climates can melt snow and glacial ice, rapidly releasing water into the drainage system and possibly causing floods.
Debris avalanche events, landslides, caldera collapse events and pyroclastic flows entering a body of water may generate a tsunami.
Drainage systems can become blocked by the deposition of pyroclastic flows and lava flows. Such blockage may create a temporary dam that could fill with water and fail resulting in floods downstream.
Volcanic earthquakes and tremors? secondary
Volcanic tremor is a type of continuous rhythmic shaking of the ground that is generated by magma moving underground.
Atmospheric effects? secondary
As large amounts of tephra and volcanic gases can be injected into the atmosphere, volcanism can have short term effects on climate.
Volcanic gases like sulphur dioxide reflect solar radiation.
What is the VEI?
The volcanic explosivity index provides a relative measure of the explosiveness of the volcanic eruptions
0=gentle and continuous flow of lava
2=occurs somewhere in world every 2 weeks
6=largest in living memory
What is the VEI?
The volcanic explosivity index provides a relative measure of the explosiveness of the volcanic eruptions
0=gentle and continuous flow of lava
2=occurs somewhere in world every 2 weeks
6=largest in living memory
Each scale is 10 times bigger than before
- volumes of products, eruption and height and qualitative observations used to determine explosivity value
Scale is open ended
What is seismic monitoring?
Scientists collect data from the instrument networks then analyse them to look for out-of-ordinary signals. Can compare data with past volcanic events and determine whether a volcano might erupt in the future.Most can be accessed from observatories but visits to the volcano occur too.
How is ground deformation used to monitor volcanoes?,
Measured using tiltmeters and laser-based electronic distance measurement. Bulging (inflation) of the ground is caused by rising magma. Both slope angles and the increasing distance between set points can be measured accurately.
How are gas measurements used to monitor volcanoes?
Deep beneath the surface, gases are dissolved in magma, but as magma rises toward the surface the pressure decreases and gases separate from the liquid. Because gas is less dense than magma, it may rise more quickly and be detected at the surface of the earth.
Gas released from a volcano relates directly to the type, amount, and depth of magma beneath the surface. An increase in gas output, the appearance of new vents, or a change in the chemical makeup of the gas and water can be some of the first aboveground signs of heightened volcanic activity.
How is hydrology used to monitor volcanoes?
Monitoring water changes provides clues about the activity of the volcano. Also, understanding how water flows down the side of the volcano, it can help to understand how lava might flow.
How is heat/thermal monitoring used to monitor volcanoes?
Some volcanoes have thermal features such as steaming vents, geysers, hot springs, lava flows, or lava domes. Surface temperature changes at these thermal features sometimes occur before a volcanic eruption. Recognizing these “thermal anomalies” can be helpful in forecasting changes in activity.
Infrared satellite sensors can detect volcanic thermal features. This is an important tool for monitoring remote volcanoes with sparse ground-based equipment.
Preparedness for volcanic eruptions?
monitoring: seismicity, hydrology, ground deformations, gases
warning systems
hazard mapping: past events can be mapped eg pyroclastic flows
Mitigation for volcanic eruptions?
evacuation=key strategy
diversion of lava (less effective)- earth embankments at mount etna
spraying water on lava
Prevention for volcanic activities?
not possible
may be possible to stop some volcanic hazards
Lake Kiva, degassing of carbon dioxide - removal of deep stores within the lakes safely. if all released it would poison everyone.
Adaption for volcanic eruptions?
property design eg ash resistant tiles, steeply pitches roof so ash doesn’t gather, window seals
land use planning
adapting behaviours eg in Mazukus they use goats to show the effects of poisonous gas (education)
Factors affecting the effectiveness of approaches?
Population density: harder to evacuate, more property damage, difficult to land use plan. smaller population density means condensed area to protect
Economic factors: cannot afford to update property design, poor economy might not be able to afford prediction, if dependant on agricultural destruction of rural land is fatal.
Hazard perception: fatalistic means that they won’t adapt, so effects will be worse. However, fear means people will leave so fewer people to effect and therefore easier.
What is the focus on an earthquake?
The focus is the point within the crust where the plates give way. The point of greatest energy. Seismic waves travel out from here.
What is the epicentre of an earthquake?
The point on the earth’s surface directly above the focus. Usually the most hazardous location.
What are seismic waves?
Waves of energy caused by sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.
What are body waves?
Travels within the body of earth
What are primary waves? body
P waves fastest 5.5km/second compressed waves 'balls in a line' travel through both the mantle and core arrives first at a detector
What are secondary waves? body
S waves
much slower
vibrate at right angles to direction of travel ‘ shake like a skipping rope’
travels through the mantle but not through the core, only through solid matter
arrive second at the detector
What are surface waves?
slower, travel on the surface, lower frequency, larger amplitude
What are love waves? surface
cause the ground to move sideways, and do most of the damage in eathquakes.
What are rayleigh waves? surface
Cause the round to move up and down.
Describe what is shown on a seismograph
A seismograph/seisometer is used to measure seismic waves using a weight, pen and moving drum
The P waves will be the first wiggle that is bigger than the rest of the little ones (microseisms). P waves are the fastest seismic waves. The next set are the S waves. These are usually bigger than P waves.
If no S waves are marked on the seisogram then the earthquake may have been recorded on the other side of the world because S waves cannot travel through the liquid layers of the earth.
Surface waves are larger waves marked on the seismogram, they have a lower frequency and are slower than P waves.
Describe the distribution of earthquakes?
Occur at all types of boundaries but the most powerful ones are found where huge pressure builds up eg convergent or conservative
Distribution closely linked to tectonic plates
What is the richter scale?
Measures magnitude of earthquakes i.e the energy released
it is logarithmic scale based on 10
based on the amplitude of the wave
each unit represents a 10x increase in amplitude and 32x increase in energy released
What is the Moment Magnitude Scale?
Based on:
distance that rock slides along a fault surface after it breaks, called the fault slip
the area of the fault surface that is actually broken by the earthquakes
a measurement of how rigid the rocks are near the broken fault
(energy released based on physical properties of the area not just the amplitude of the waves.
What is the Mercalli Scale?
Measures intensity of impacts of an earthquake from 1-x11. Based on the movement of buildings.
Describe the predictability of earthquakes?
reliable prediction is very difficult
95% associated with plate margins so these are regions of risk
areas of faults that are likely to slip and cause earthquakes can be identified
short term prediction: groundwater chemistry
Describe the randomness of earthquakes?
Quasi-random: not all linked to 2 plate tectonics, timing differences
What is the frequency-magnitude relationship of earthquakes?
Inverse relationship
Biggest magnitude=less frequent
What are the primary hazards associated with earthquakes?
Groundshaking: body waves: P and S waves surface waves: rayleigh and love waves. Underlying geology will affect ground shaking e.g. unconsolidated rock amplifies waves. Seismic lensing: reflection at a geological boundary.
What secondary hazards are associated with earthquakes?
Tsunamis: earthquake has to trigger a vertical displacement of the sea bed. Most occur on subduction boundaries.
