Geography - Hazards

GO back to booklet 3 onward and check AO1 is in there

What is a hazard?

A potential threat to human life and property caused by an event. Hazards can be human or natural.

Hazard risk equation

Risk = Hazard x Vulnerability / Capacity to cope

Natural disasters vs. Hazards

Hazards shouldn’t be confused with natural disasters, which only occur when a vulnerable population is exposed to a hazard. If the population is not vulnerable the hazard will not have a significant effect, so the event won’t be disastrous.

3 major types of geographical hazards

Geophysical

Atmospheric

Hydrological

What causes the 3 major types of hazards

Geophysical - Hazards caused by land processes, majorly tectonic plates (e.g. Volcanic eruptions) - Comes from Earth’s Energy

Atmospheric - Hazards caused by atmospheric processes and the conditions created because of these, such as weather systems (e.g. Wildfires) - Comes from Solar Energy

Hydrological - Hazards caused by water bodies and movement (e.g. Floods) - Comes from Solar Energy

Hazards can be classed as a mixture of these geographical processes (give an example)

A tropical storm could be classed as a hydrological-atmospheric/hydrometeorological hazard as both these processes contribute to the hazard.

What is the Lithosphere and what hazards form there?

The Lithosphere is the solid rock beneath our feet (at the top of the mantle)

Geophysical - Avalanche, Tsunamis, Earthquakes, Mass Movement, Volcanic activity

Atmospheric - Wildfires

Hydrological - Drought, Floods

What is the Hydrosphere and what hazards are from there?

All the water on the Earth’s surface

Geophysical - Coastal Flooding, Storm Surge

Why can Atmospheric hazards be seen as the most dangerous

• Frequent

• Feedback - e.g. Wildfires emit CO2 into the atmosphere which causes more intense Wildfires which emit more CO2 and therefore cause more global warming

• Global scale of impact - Global warming

Category of hazards (sudden onset / slow-onset)

Sudden onset hazards are hazards that emerge quickly or unexpectedly e.g. wildfires/earthquakes

Slow-onset hazards emerge gradually over-time e.g. Drought

Aspects which affect the impact of a hazard

Incidence (frequency) SCALE (temporal)

Intensity (power) SCALE (size)

Magnitude (size) - Can be partly how a hazards’ intensity is measured

Distribution (Where it occurs)

Level of development - Economic development affects how people respond to a hazardous event, so a hazard of the same magnitude may have very different impacts in 2 places of contrasting levels of development

Factors influencing human responses to hazards

Hazard Perception

The type of response

The park model

The Hazard Management Cycle

What is hazard perception - How does it affect human responses to hazards? (e.g. faulty, created by wealth)

The different viewpoints people have of how dangerous hazards are and what risk they pose

These perceptions can be altered by lifestyle factors such as cultural or economic factors e.g. a wealthy person may view a hazard as less dangerous as they have money to respond but a poorer person may have a more fatalistic hazard perception as they don’t have money to respond (although a wealthier person could view it as much worse due to the high property damage that may occur)

What influences hazard perception?

Wealth - May see hazard as less threatening (have ability to evacuate through transport access, have stronger buildings), may have a more adaptive mindset

OR more threatening as for the more wealthier there is greater risk of property damage and higher financial loss

Education - Those who are educated on the full effects of hazards are more likely to evacuate and may know how to prepare or respond

Religion & beliefs - Some may view hazards as being put their by God or part of a natural life cycle - may be more fatalistic

However, some may believe in environmental conservation and so they may view hazards as a huge risk to the natural environment especially because of global warming

Mobility - Those who have limited access to evacuation routes may see the hazard as a greater threat than those who have lots of evacuation routes. Whether they are in a secluded location or have a disability/illness, they can’t leave as easily so they may feel more at risk, San Francisco

Experience of hazardous events - Someone who has experienced more hazards is more likely to understand the full effects of a hazard BUT there are also people who have experienced hazards that have an optimistic and unrealistic outlook on future hazards. Similar to a ‘lightning never strikes twice’ mentality

Hazard Equation

Risk = Hazard x Vulnerability

Capacity to Cope

Types of hazard perception

Fatalistic (Haiti)

Adaptative (California)

Fear (New Orleans, Hurricane Katrina)

Explain 3 of the types of responses to hazards (Fatalism, Prediction, Adaptation) + examples

Fatalism - Viewpoint that hazards are uncontrollable natural events, and any losses should just be accepted as there is nothing that can be done to stop them

Prediction - Using scientific research and past events in order to know when a hazard will take place, so that warning can be delivered and there is time for preparation so impacts of the hazard can be reduced. In very few cases hazards can be prevented via prediction if predicted early enough e.g. predicting wildfires from climatic red flags

Adaptation (can include faulty) - Attempting to live with hazards by adjusting lifestyle choices (reduces vulnerability) e.g. retrofitting houses for earthquakes

Explain 3 more types of responses to hazards (Mitigation, Management and Risk Sharing)

Mitigation - Strategies carried out to lessen the severity of a hazard (e.g. sandbags to offset the impact of flooding)

Management - Coordinated strategies to reduce a hazard’s effects. This includes prediction, adaptation and mitigation.

Risk sharing - A form of community preparedness, whereby the community shares the risk posed by a natural hazard and invests collectively to mitigate the impacts of future hazards

Example of a place where risk sharing has worked and how?

New Zealand (multi-hazardous environment) - Canterbury Earthquake 2010 cost country 20% of it’s national GDP, there is now attempts to share the risk via insurance investment, so strategies can be put in place before the disasters rather than investing more in a clean up

Perception of natural hazards in places examples (3 places)

Haiti (rural) HP (generally) - Fatalistic

California HP (generally) - Faulty

Western New Orleans (generally) - Fearful

How social/cultural/economic characteristics of rural Haiti may influence the hazard perception

Social/Cultural

• Agricultural Subsistence farming - difficult to accumulate wealth - can’t afford good housing - +V - +Fatalistic

• High infant mortality - used to death- probably +Fatalistic

• Voodoo practice belief - see hazard as a punishment from spirits so they accept it and become more fatalistic and more die - see the hazard as not their responsiblity to stop

• Don’t fear death -they believe they live many times (believe in reincarnation) - naive

Economic

• Poor 4th world status - Poorest country in the Western Hemisphere - not enough money to defend - houses are self built and poor quality - +Fatalism

• Trade policies lowered food prices so farmers struggle

Poltical/Economic

• No government interference - May feel like they have no help - +fatalistic

How social/cultural/economic characteristics of California may influence the hazard perception

Environmental

• Built earthquake resistance measures e.g. retrofitting

Social/Cultural

• Disaster command centre - provides internal and external information and allocates resources based on pre-planned responses

• Huge collaborations from different groups

• Learn from previous events (experience) - +knowledge

Economic

• Funds from other HICs allow huge preparation and community preparedness via organisations such as Cal OES which coordinate emergency preparations, response and recovery

• $600M public safety budget

• $9M federal funds

Socio-economic

• 5th largest economy in the world - (roughly) $3.2T GDP 2019 - more opportunities created for people to educate themselves via websites such as

What is the Park Model?

A graphical representation of how quality of life is affected by a hazard overtime and how quickly human response leads to a recovery from it

What does the Park Model show?

The steps carried out in the recovery after a hazard, giving a rough indication of time frame

The 3 stages of the Park Model

Relief

Rehabilitation

Reconstruction

Explain the stages of the Park Model

Relief - Stage 1 (hours-days)

• Immediate local response - medical aid, search and rescue

• Immediate appeal for foreign aid - global response

Rehabilitation - Stage 2 (days-weeks)

• Services begin to be restored

• Temporary hospitals and shelters set up

• Food and water distributed

• Coordinated foreign aid e.g. peacekeeping forces

Reconstruction - Stage 3 (weeks-years)

• Restoring the area to the same or better QOL

• Area back to normal - ecosystem restored and crops regrown

• Infrastructure rebuilt

• Mitigation efforts for future events

The Park Model also works as a control line (a line which provides a basline for comparison) to compare hazards. True or False?

TRUE

An extremely catastrophic hazard would have a steeper curve and a slower recovery time than average

The Hazard Management Cycle - What is it?

A continuous cycle which outlines the stages of responding to hazardous events, showing how the same stages take place after every hazard

4 stages of the HMC cycle

Preparedness

(Event)

Response

Recovery

Mitigation

Explain the 4 stages of the HMC

Preparedness - Being ready for an event to occur (public awareness, education, training)

Response - Immediate action taken after the event (evacuation, medical assistance, rescue)

Recovery - Long-term responses (restoring services, reconstruction)

Mitigation - Strategies to lessen effects of another hazard (barriers, warning signals, observatories)

Evaluating the effectiveness of the models (HMC & Park)

• Can it be applied to every hazard? - Would some require a more complex model?

• Do the models take into account any aspects of hazardous events such as the level of development

• Is there a timeframe of the events? - Time taken for each response and how these responses change due to aspects of the hazard e.g. intensity

• Less vague? - Can all steps be applied to all hazardous events?

• Does the model present hazards currently? - altercations possibly made due to Climate Change? - will the model eventually not accurately represent human responses - e.g. could the HMC stop because hazards will occur more frequently than the mitigation strategies will occur? - Wildfires?

5 aspects of hazards and how they affect human responses (Incidence)

Frequency of a hazard - how often it occurs

• Low incidence hazards may be harder to predict and have less management strategies put in place so the hazard could have more impact

• Low incidence hazards are usually more intense than high incidence ones

• e.g. only 36 earthquakes recorded since 1500 that were a magnitude of 8.5 or higher, but there have been millions of earthquakes that have occurred annually but have been too weak to record

5 aspects of hazards and how they affect human responses (Distribution)

Where the hazards occur geographically

• Areas of high hazard distribution are likely to have a lot of management strategies, and those living there will be adapted to the hazardous landscape because it dominates the area more so than in places with low hazard distribution

5 aspects of hazards and how they affect human responses (Magnitude / Intensity)

High magnitude and high intensity hazards will have worse effects so they’ll require more management e.g. more mitigation strategies will be required to lessen the effects and ensure a quick recovery and return to normal life

Magnitude and Intensity are different

Magnitude can be defined by a number intensity can’t

Intensity is the effect of the hazard (large impact + large intensity)

Intensity can be changed by different factors depending on the hazard e.g. how close trees are when a wildfire occurs

5 aspects of hazards and how they affect human responses (Level of development)

How these countries use their development for mitigation, good planning is needed like in California the FEMA

Economic development will affect how someone can respond to a hazard so a hazard with the same magnitude may have very different impacts in 2 different places with contrasting development

However, sometimes HICs may be unprepared for a hazard and have a lack of management strategies in place. This is especially the case in multi-hazardous environments where resources are spread thinly over a variety of areas that are vulnerable to hazards

Hazards - Plate Tectonics: Structure of the Earth (Top to core)

Crust - The thin top of the Lithosphere, between only 0-100km thick

Mantle - mainly solid rock, and the rocks are high in silicon, makes up 84% of Earth’s volume. Made up of the Lithosphere which rests on top, and below that is semi molten magma (the asthenosphere)

Outer Core - Semi-molten, iron/nickel

Inner Core - Solid ball of iron/nickel, very hot due to pressure and radioactive decay (contains elements such as Uranium that give off heat as they decompose), the heat from here is responsible for the Earth’s internal energy and it spreads through it, compressed and very dense, roughly 5000 degrees Celsius - mostly primordial heat energy (heat left from the Earth’s formation) & Radiogenic heat energy (radioactive energy from the radioactive decay of isotopes), growing as the liquid outer core turns into solid inner core due to pressure

Structure of the Earth Pt 2 - Lithosphere and Asthenosphere

Lithosphere - Crust + upper mantle, broken up into plates, majority is within the mantle, the top of the Lithosphere is the crust which is the land and sea we live on

Asthenosphere - Just below Lithosphere (within the Mantle), semi-molten layer which constantly moves due to convection currents (flows of heat), movements are powered by heat from the core

The Plate Tectonic Theory

The Lithosphere is broken up into large slabs of rock called Tectonic plates.

These move due to the convection currents in the asthenosphere, which push and pull the plates in different directions. CC are caused when less dense magma rises, cools then sinks. The edges of where the plates meet are called plate boundaries (or plate margins)

Evaluating evidence of Plate Tectonic Theory

(weakest and oldest) Continental fit - Continents fit together like a jigsaw, no proof

Geological evidence - Rocks (use age of rocks to trace plate movements) , fossils (tell us where plants and animals may have lived in the past which helps reveal where plates may have once fit together) and glacial striations (gouges or scratches into bedrock by glacial abrasion) proved movement of plates and showed direction

Presence of ocean ridges and trenches - Shows plates are being moved and destroyed

Palaeomagnetism - Rocks align with the current magnetic field and will face a specific way, there is magnetic striping on the Earth where there are lanes of rocks which face opposite ways across Earth, this pattern is symmetrical and so this shows that not only poles swap over long periods of time but also that plates move, as rocks which are of equal distance away from a certain point will point in the same direction; since these rocks point in the same direction it makes sense that at some point they were together in one place and that they moved apart

Satellite measurements of plate movement - Proves plates are moving and shows direction accurately

(Strongest and newest) Location of seismic activity - Shows that some areas of crust are moving faster than others and proves the slab pull mechanism

MOVEMENT/DIRECTION/SPEED

Convection currents and magma, how do they cause magma to move through the Earth?

Heat from the inner core moves via convection through the mantle and into the asthenosphere

Then hot magma rises as it becomes less dense with the heat that originally came from the inner core

Magma is cooler at the top as it’s further away from the heat source; it cools becomes more dense and then sinks back down to the bottom of the asthenosphere

Cooler magma is reheated and begins to rise again, creating a loop called a convection current

3 Types of plate boundaries

Constructive (divergent) - plates move away from each other

Destructive (convergent) - plates move towards each other

Conservative - plates move parallel to each other

How does a continental and oceanic destructive PB interact?

• The denser oceanic plate subducts below the continental plate

• The plate subducting leaves a deep ocean trench

• (Fold mountains occur when sediment is pushed upwards during subduction)

• The oceanic crust is melted as it subducts into the asthenosphere

• The extra magma created causes pressure to build up

• Pressurised magma forces through weak areas in the continental plate

• Explosive high pressure volcanoes erupt through the continental plate, known as composite volcanoes

How do 2 oceanic plates interact at a destructive plate boundary?

• The heavier plate subducts leaving an ocean trench. (Fold mountains will also occur)

• Built up pressure causes underwater volcanoes bursting through oceanic plate

• Lava cools and creates new land called island arcs

How do 2 continental plates interact at a destructive plate boundary?

• Both plates are not as dense as oceanic plates so lots of pressure builds

• Ancient oceanic crust is subducted slightly, but there is no subduction of continental crust

• Pile up of continental crust on top of the Lithosphere due to pressure between the plates

• Fold mountains are formed from piles of continental crust

How do 2 oceanic plates interact at a constructive plate boundary?

• Magma rises between the gap left by the two plates separating, forming new land when it cools

• Less explosive underwater volcanoes are formed as magma rises

• The new land formed on the ocean floor by lava filling the gaps is known as a mid-ocean ridge (e.g. Mid-Atlantic Ridge) - This process of the plates moving apart, creating new ocean floor is known as sea-floor spreading

Proof of plate movement and sea floor spreading

Theorised by Harry Hess in 1940s

Palaeomagnetism - The study of rocks that show the magnetic fields of the Earth. As new rock is formed and cools, the magnetic grains within the rock align with the magnetic poles. Our poles (north and south) switch periodically is what it shows. Each time they switch the new rocks formed at the PB align in the opposite direction to the older rock. On the ocean floor either side of the constructive PB, geologists observed that there are symmetrical bands of rock with alternating bands of magnetic polarity. This is evidence of sea floor spreading.

Do volcanoes always form on PBs?

Volcanoes DO NOT always form on PBs, they can form via hotspots (where magma from the Earth’s mantle rise up to the surface causing a volcanism)

How destructive (convergent) boundaries occur

Oceanic plate and continental plate meet and the more dense oceanic plate is forced under the less dense continental plate, subducting into a subduction zone

How any crusts interact at conservative plate boundaries?

Between any crust, the parallel plates move in different directions or at different speeds.

No plates are destroyed so no landforms are created.

When these plates move a lot of pressure builds up.

On oceanic crust this can cause lots of displacement of water.

On continental crust fault lines can occur where the ground is cracked by the movement.

Pressure if released as an Earthquake.

[Shallow focus here for Earthquakes]

• NO magma, just friction & so no volcanoes, Earthquakes only form here

VEI scale measures what and what does it go up to?

Volcanic explosively index measures the size of volcanic eruptions, it goes from 0-8 and is logarithmic

Hotspots - what are they?

Areas of volcanic activity that are not related to plate boundaries.

Hot magma plumes from the mantle rise and burn through weaker parts of the crust.

This can create volcanoes and islands.

The plumes stay in the same place but the plates continue to move, which sometimes causes a chain of islands (e.g. Hawaii)

Lava viscosity and how it affects volcanism (eruptions) and why?

More viscous lava is more thick and sticky, furthermore they come from composite (steep-sided) volcanoes and less viscous lava comes from shield volcanoes like in Hawaii.

More viscous lava generally creates more explosive eruptions and less viscous lava generally creates more effusive eruptions.

This is because viscous lava will trap pockets of gas within the rock, and not let them pop so pressure builds up and eruptions can be explosive.

Silica content and how it affects viscosity

If the lava has a high silica content it will be more viscous, for example if the lava is made from a high proportion of rhyolite (a type of rock) it will be more viscous but if the lava is basaltic lava then it has a much lower viscosity as basalt has a lower silica content.

Low viscosity = Faster

Hazards caused by volcanoes (primary and secondary)

Primary - Lava flows, Tephra (the general name given to anything thrown into the air during a volcanic eruption), Toxic gases, Nuees ardentes/pyroclastic flows (a super-heated mixture of gas and tephra that flows at speeds of up to 700 km per hour)

Secondary - Lahars (mudflow), Glacial floods, Acid rain (from sulphur dioxide gas release from eruption)

Explain the hazards caused by volcanoes

Lava flows - Lava can flow speed is determined by lava viscosity - depends on silica content, silica makes lava viscous and slow, high silica = more explosive eruptions - Kilauea volcano numerous eruptions in Hawaii

Lahars (mudflows) - caused by a number of reasons, usually melting ice at high latitudes

Glacial floods - When temp is high from hot magma, glaciers/ice sheets melt quickly causing a large amount of water to be discharged

Tephra - any type of rock that is ejected by a volcano - (Rock slides caused by Tephra) which occurred after Eyjafjallajökull erupted

Toxic gases - release during some eruptions, even CO2 can be toxic as it can replace oxygen as it is heavier - Mt Nyiragongo

Acid rain - caused when gases such as sulphur dioxide are released into the atmosphere

Nuees ardentes/pyroclastic flows - clouds of burning hot ash and gas that collapse down a volcano at high speeds ~60 mph average can reach up to 400mph!

Spatial distribution of volcanoes

Along constructive or destructive PBs, or located on hotspots.

the Ring of Fire is an area of high volcanic and earthquake activity (north of Pacific Plate, in the Pacific) and the majority of large volcanic are along a 25,000 mile belt along the north of the Pacific plate boundary

Magnitude of volcanoes

Vulcanicity is measured on the VEI (Volcanic Explosivity Index). Logarithmic scale from VEI 2 onwards. Intense high magnitude eruptions are explosive whereas, calmer lower magnitude eruptions are effusive.

Frequency of volcanoes

Varies per volcano. Estimated 50-60 volcanoes erupt each month. Usually a higher frequency means a more effusive eruption and a lower frequency means more explosive eruptions. e.g. Hawaii daily has many non-explosive (0 VEI) eruptions but Plinian (highly explosive) eruptions occur very rarely every century or even millennium, e.g. eruption of Mt Vesuvius in 79AD (VEI 5)

Volcanic eruptions characteristics in correlation to PBs

Constructive PBs strongly linked to effusive eruptions with lots of basalt rock lava (low silica content)

Destructive PBs strongly linked to explosive eruptions with lots of rhyolite rock in lava (high silica content)

Some eruptions are irregular and may not fit patterns. (no earthquakes at conservative PB)

Predictability of volcanic eruptions

Regularity of eruptions can help determine when eruptions will take place (e.g. every 10 years)

Seismic activity, gases releasing and elevation etc… can all indicate an imminent eruption, but there is no definite predictions to a volcanic eruption.

Primary effects of volcanic hazards (Environmental Economic, Social, Political)

Env = Ecosystems damaged through various volcanic hazards, wildlife killed

Eco = Business and industries destroyed or disrupted

Social = Death or injury, Homes destroyed from lava/pyroclastic flows

Political = govt. buildings destroyed

Secondary effects of volcanic hazards (Environmental Economic, Social, Political)

Env = Water acidified by acid rain (also social), volcanic gases e.g. CO₂ contribute to the greenhouse effect (global warming)

Eco = Jobs lost, Profit from tourist industry (after eruption)

Social = Fires can start which puts lives at risk, Mudflows or floods (floods can lead to disease outbreak e.g. Cholera), Trauma, Homelessness

Political = Conflict may arise concerning govt. response e.g. food shortages or insurance etc…

Eruption of Eyjafjallajökull - characteristics of the hazard and the place (Iceland) & impact 2010

Hazard

Highly explosive

Remobilization of ash

1 month eruption

VEI 4

Constructive PB

Glaciers melted causing flooding of up to 3000 cubic meters per second through the River Markarfljot

Place

HDI - 0.949 (V. high)

No one lives below the poverty line = low vulnerability

Rural area

Sparsely populated (roughly 3/km2)

Extensive management including land use planning & education

Impact

0 deaths

£130m daily cost to airlines

Homes & roads damaged & services disrupted, crops damaged, by ash and roads washed away

Eruption of Mt. Nyiragongo - Characteristics of the hazard, place and impact DRC (Africa) 2002

Example of a place where secondary effects cause more chaos

Hazard

Constructive PB

Large basaltic stratovolcano

VE1

Fast-moving ultra-mafic lava (very low silica content) (90mph)

Place

Densely populated

Epicenter 15km from Goma (city which is highly vulnerable) - Earthquake result of eruption

HDI = 0.48

$1000 GNI = low tax = bad infrastructure = vulnerability

DRC recovering from decade long war = no coordination to defend people = vulnerability

Impact

1/3 of Goma destroyed

150-200 dead

Drinking water poisoned - Dysentery

Response to volcanic hazards

Prevention & Mitigation - Eruptions can’t be prevented, however the risk to people can be almost eliminated entirely by e.g. not allowing buildings within a certain proximity of the volcano. Direct intervention with the volcano e.g. concrete blocks to steer lava away from areas of risk, strengthen areas that are at risk of mudflow or ash pileup, Evacuation and exclusion zones, Mitigate effects on health by having emergency aid and rescue

Preparedness - Monitoring the volcano activity means that warnings can be given out (can also mitigate), Education on what people need to do if there is an eruption, planned evacuation procedures, Training response teams

Adaptation (Response) - Capitalize on opportunities such as encouraging tourism

Recovery

Response to volcanic hazards - Iceland (Eyjafjallajökull)

Prevention & Mitigation - Ongoing monitoring - hundreds of small earthquakes caused by magma as it rises up through the cracks in the Earth’s crust occur & temp around volcano rises as activity increases & when a volcano is close to erupting it starts to release gas which has a high sulphur content, board up houses

Preparation - Ongoing monitoring of volcanic activity

Response - (adaptation) - Rebuild houses (state subsidies/insurance), mostly pasture land which returns quickly, lessons learnt for future management, Red Cross offered supplies and resources to those displaced and evacuated

Recovery - Government rebuilt destroyed roads and infrastructure in under 2 months to reconnect many remote settlements, which prior had to rely on boats and helicopter imported supplies

Response to volcanic hazards (Mt. Nyiragongo)

Prevention & Mitigation - Very little

Preparation - As this was an LIC at the time very few people were educated on the dangers

Response - ‘Red Alert’ issued

Recovery - Very badly coordinated due to weak local governance, Reliant on aid, US provided $7.5M in direct funding aid to the DRC to help with reconstruction efforts, Due to corrupt government many locals had to recover themselves

Seismic hazards - The focus & epicentre & how does a shallow focus affect an earthquake’s magnitude?

The focus is the point underground where the earthquake originates from. The epicentre is the area above ground which that is directly above the focus (shockwaves are released from here).

Shallow focus = stronger earthquake

Seismic hazards - spatial distribution

The Ring of Fire accounts for 90% of the world’s Earthquakes & it runs along the borders of 4 continents (N.America, S.America, Asia & Oceania)

The Alpine-Himalayan belt accounts for 5-6% of the world’s Earthquakes (from SE Asia to W Europe)

Seismic hazards - magnitude, how is it measured and what affects it?

Measured using…

Seismicity is measured using the logarithmic Richter Scale which is a measure of strength of seismic waves (uses numbers from 0-10)

The Modified Mercalli Intensity Scale can also be used, 1-12 (roman numerals), it is subjective which means it is disputed as it is dependent on human development being present rather than the strength of the seismic waves

PB type…

The magnitude of the earthquake is also dependent on the depth of the focus. Conservative PB have the shallowest focus so the waves have to travel less distance to reach the epicenter so the seismic waves are stronger.

Destructive boundaries usually have deeper focuses, meaning the seismic waves are spread over a large area before they reach the epicenter so the seismic waves are weaker.

Seismic hazards - frequency

Frequent - occur daily around the world.

Hundreds of really small earthquakes can’t be felt by humans and larger earthquakes that can be will happen less often.

Seismic hazards - Spatial and Temporal SCALE

Earthquakes follow no pattern and are random so there is irregularity between events.

Seismic hazards - Predictability

Earthquakes are almost impossible to predict. Microquakes give some indication but the magnitude can’t be predicted as how strong they are is random.

Nowcasting has been used although it is not so effective

Hazards cause by seismic activity (primary and secondary)

• Shockwaves (seismic waves) - When 2 plates move side by side, friction builds up and pressure increases; this pressure is stored as potential energy, it can’t move so it just builds. When the pressure becomes, the plates eventually move. All of the energy built must go somewhere, so it’s transferred into kinetic energy, which is released and vibrates throughout the ground. Further from focus = weaker shockwaves as the energy is transferred to the surroundings

• Tsunamis - When an oceanic crust is jolted during an earthquake, all of the water above this placed is displaced, the water travels fast but with a low amplitude (height), as it gets closer to the coast, the sea level decreases so there is friction between the sea bed and the waves. This causes the waves to slow down and gain height, creating a wall of water that is on average 10ft high and can reach up to 100ft

• Liquefaction - When soil is saturated, the vibrations of an earthquake cause it to act like a liquid. Soil becomes weaker and more likely to subside when it has a large weight on it

• Ground rupture

• Building collapse - Ruptured gas lines - possible fire

• Avalanches / landslides

Seismic hazards - Intensity in relation to areal extent

Primary hazards caused by seismic hazards - Generally high intensity and low areal extent

Secondary hazards caused by seismic hazards - Generally still high (not as high) intensity and larger areal extent

Case Study: South Napa Earthquake 2014 (CA)

(Characteristics + impacts + responses) + Facts

Prevention and mitigation: Can’t prevent it, there was retrofitting

Prep: Experimental earthquake warning systems (only warned seismologists seconds before the event occurred)

Response: Warning issued, due to short time between warning and event it barely had an impact

Recovery: 200 injured people treated at Queen of the Valley Medical Centre in Napa.

Facts

6 Richter Scale

Conservative PB (11km shallower focus)

1 death

$360M+ damages cost due to fire

Good government - Land use planning in place

Case Study: Haiti Earthquake 2010

(Characteristics + Impacts + Responses)

Prep: Barely any due to poor governance (this also affected recovery)

Response: 4M received food aid and 1.5M received emergency shelter materials,

Recovery: ‘Hope for Haiti’ Telethon raised $60M within a few days

Mitigation: The World Bank (intergovernmental organization) trained over 100 ministry officials in Haiti (next time better response?)

7 Richter Scale

Poorest country in the western hemisphere

Destructive PB

Focus deep at 13km

Over $10B damages (120% GDP) Haiti

Over 200,000 died and almost 4,000,000 affected Haiti

Primary effects of seismic hazards (economic, environmental, Social, Political)

Environmental - Earthquakes can cause fault lines which destroy the environment, Liquefaction

Economic - Business destroyed, damages

Social - Building collapse (death/injury/trapping them)

Political - Govt. buildings destroyed

Secondary effects of seismic hazards (economic, environmental, Social, Political)

Environmental - Radioactive materials and other dangerous substances leaked from power plants, saltwater from tsunamis flood freshwater ecosystems, soil salinization

Economic - Economic decline (negative multiplier effect) as businesses are destroyed (tax breaks etc.…), high cost of rebuilding and insurance payout, sources of income lost

Social - Gas pipes rupturing, starting fires which can kill, water supplies are contaminated as pipes burst spreading disease and causing floods, tsunamis lead to damaging flooding

Political - Political unrest from food/water shortages, borrowing money for international aid, can be initial chaos and ‘lawlessness’ e.g. looting

Response and Risk management to seismic hazards

Prevention - Majority can’t be prevented (earthquakes and tsunamis will occur regardless), liquefaction of soils can be prevented through soil stabilization (gravel columns can be put in the ground), avalanches can be prevented through controlled explosions

Preparedness - Earthquake prone areas e.g. Japan have extensive awareness strategies and education in place e.g. Drop, Cover and Hold On, Earthquake/Tsunami warning systems after an earthquake. Earthquakes can’t be predicted

Mitigation - Search and rescue: immediate emergency aid, evacuation (short term), demolishing older unsafe buildings, Tsunami wave breaks and sea walls

Adaptation - Move away from an area at risk, capitalize on opportunities such as encouraging tourism, insurance if living in a place at risk, changing lifestyle choices e.g. moving valuable items so they can’t fall and break, building especially designed ‘earthquake proof’ buildings (retrofitting)

Factors that affect the magnitude/intensity of a seismic hazard event

(H) in the hazard equation

Geology

PB type

Depth of focus

Position of epicentre

Silica content of magma (volcanic)

Frequency, magnitude and predictability

The occurrence of secondary hazards

Topography

Storm hazards - what is a tropical storm?

A tropical storm is a low pressure, spinning storm with high winds and torrential rain

What conditions are needed for tropical storms to develop? (Temp, Air pressure, Wind shear, rotation, trigger)

Temperature - Ocean temp must be 26-27 degrees Celsius and at least 50 meters deep. Warm water provides the storm with energy

Air pressure - Must be in areas of unstable air pressure, usually where areas of HP and LP meet (convergence), so that warm air rises more readily and clouds can form (this air must also be humid for cloud formation). Warmer air rises as it is less dense then cold air

Wind shear - Wind must be present for the swirling motion to form but it can’t be too strong or the storm system will be ripped apart in the early stages

Rotation - Can only form around the equator but no less than 5 degrees latitude (generally between 5-30). The Coriolis effect is the effect of the Earth’s rotation on weather events. The storm spins because the Earth is spinning; but there is no Coriolis Effect at the equator, so that’s why storms only form a certain distance away from the equator

A trigger - Pre-existing thunder storm, a spot of very high sea surface temp, an area of LP and other factors can act as a trigger for a storm to develop, which will only develop further once the other conditions are present

The formation of Tropical Storms (first 4 steps)

1.) Warm, moist air rises, leaving an area of LP below. Causing warm air from the surrounding areas of HP to move into this LP area and rise too. Here, warm air is constantly rising and accumulating in the atmosphere

2.) When the warm air rises, it cools, condensing into big thunderstorm clouds (cumulonimbus clouds)

3.) The whole system is spinning due to the Coriolis effect. SH: clockwise NH: anticlockwise

4.) Constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds. At 39mph the storm = Tropical Storm

The formation of Tropical Storms (last 4 steps)

5.) Centre - eye, 30 miles wide, extreme LP area. Cool, dry air descends from the sky (cooler higher altitudes and moisture is transferred to the TS) descends into the eye, causing the weather to be relatively calm and cloud free. The more intense TS, the clearer the eye

6.) Eye wall surround the eye; it’s the most powerful part of the storm. Warm, moist air rises rapidly here, with extremely high wind speeds and torrential rain. When winds reach 74mph, it becomes a hurricane/cyclone/typhoon

7.) When the TS reaches a coast, the LP and high winds will cause a large amount of sea water to be taken into the system and then released as a storm sure (high wave)

8.) When the storm reaches land, it no longer has a supply of energy (warm, moist air from the sea) and the eyes eventually collapses. It does eventually fade however, heavy rain can occur for days after

Spatial distribution of TS (Typhoons, Hurricanes and Cyclones)

Typhoons - South East of Asia (account for roughly 1/3 of all storms)

Hurricanes - South west and south east of North America (Caribbean Sea / Gulf of Mexico)

Cyclones - West and east of Australia (Arabian Sea / Bay of Bengal)

Form in belts 5-20 N & S of the equator because the Coriolis force occurs strongly here as it needs some distance from the equator to start to spin low pressure systems

They generally track westwards as the equator is home to easterly winds which spin due to the Coriolis force

Magnitude of TS - Scale it’s measured on?

Measured on the Saffir-Simpson Scale (a scale of 1-5) based on wind speed and thus the power of the storm

Frequency of TS

Tropical Storms form in the NH from June-November and in the SH from November-April (almost all year round) and the majority of TS don’t develop into strong storms and don’t reach land. However strong TS that do reach land are becoming increasingly frequent.

Note: more land in NH than SH due to more land being in NH

Regularity of TS

Irregular because their path doesn’t follow a set route although they do occur in the same rough areas. The route taken depends on the storm and the climatic conditions

Predictability of TS

TS form far away from land meaning satellite tracking of cloud formations and movement can be tracked and the general route can be predicted, an example is hurricane Florence which was estimated to the exact hour when it would hit

The closer a hurricane gets, the easier it is to predict. SS can also be predicted based on the pressure and intensity of the storm

From past storms and climatic trends, the probability of a storm hitting an area can also be predicted. Scientists can predict how many years it will take for a TS to hit certain areas

Hazards caused by TS

(primary) High winds - can be over 300km/h, blow houses down and heavy debris at high speeds causing injury or damage to anything it comes into contact with

(secondary) Flooding - Coastal/river flooding from SS and heavy rain. River flooding causes floods to spread and affect a larger scale of area

(secondary) Landslides - Due to the soil becoming heavy after high levels of rain

(secondary) Storm Surges/tsunamis - Large rise in sea levels caused by LP and high winds, pushing water towards the coast

Primary effects of TS hazards (Environmental, Economic, Social and Political)

Environmental - Beaches eroded, Sand displaced, Coastal habitats e.g. coral reefs are destroyed

Economic - Businesses destroyed, agricultural land damaged

Social - Drowning, debris carried by high winds can injure or kill, buildings are destroyed

Political - Government buildings are destroyed

Secondary effects of TS hazards (Environmental, Economic, Social and Political)

Environmental - River flooding / salt water contamination, animals displaced from flooding e.g. alligators (disrupt food chain?), Water sources change course from blockages

Economic - Rebuilding and insurance payout, sources on income lost, Economic decline from sources of income destroyed (negative multiplier effect)

Social - Homelessness, polluted water supplies lead to disease e.g. cholera, food shortages from damaged land

Political - Issues paying back international aid, pressure on government to do more about global warming

Storm Hazard CS - Hurricane Katrina, New Orleans USA 2005 (Hazard + Impact + Character) + A key response made by New Orleans govt

H: Heavy rainfall (380mm depth in some places), very fast wind (280 kmph), storm surge (roughly 28 ft high), Disease e.g. Vibrio illness and building collapse

I: 1,800 died, 300,000 houses destroyed, 80% of New Orleans flooded, 90 miles of beach lost, 3M without electricity & water, water became polluted with sewage and chemicals leading to a food and water shortage, 1M displaced

COP:

Economic - ¼ below poverty line , low tax base led to low levels of maintenance of levees, inadequate insurance provision, $80B loss overall

Socio-economic - Roughly 0.9 HDI

Socio-political - State of emergency not declared until 48 hours before the event leaving insufficient time for evacuation, emergency rescue & relief efforts were delayed due to lack of co-ordination as the FEMA (Federal Emergency Management Agency) didn’t act on models which predicted disaster

Response (mitigation): New Orleans govt bought houses after Hurricane Katrina to get homeowners to relocate (to reduce impacts next time)

Storm Hazard CS - Typhoon Haiyan, Philippines 2013 (Hazard + Impact + Character)

H: Severe winds (314 kmph), Heavy rainfall (300mm in one area of the Philippines in under 12 hours), Flooding, Landslides, Building collapse, Cholera

I: $12B loss estimated overall, 6,000 dead, 2M homeless, 6M displaced, All properties were destroyed, Airport damaged by storm surge, Low-lying areas on the east side of Tacloban were washed away

COP:

Environmental - Low-lying archipelago (group of islands with cities on them), no extensive defences

Economic - Rapidly industrialising & urbanising (1/3 live in poverty), speed of development hinders land use planning, low tax base limits investment in emergency response, rapid urbanisation concentrating people in vulnerable areas

Socio-cultural - Many lack education, rapidly growing population

Socio-political - Inefficient hazard management e.g. weak typhoon shelters, a state of emergency was declared but widespread looting & violence took place and local government virtually collapsed due to the loss of city officials as they were victims to the hazard

Response and Risk Management to Storm Hazards

Prevention - Tropical storms can’t be prevented, however mitigation strategies could prevent higher categories of storm

Preparedness - Education to raise awareness of what to do during a TS, evacuation plans and training, satellite image tracking to work out which areas at risk, storm warning systems and television broadcasts tracking the storm

Mitigation - Search and rescue, immediate emergency aid (short-term), Reinforcing the home but improving infrastructure e.g. roof strengthening, Cleaning loose debris before storms

Adaptation - Move away from areas at risk, design buildings to stand high winds and flood damage, Flood defences such as houses on stilts, coastal walls, river levees etc…

Wildfires & Why are they potentially so dangerous (hint - Positive Feedback)

A large, uncontrolled fire that spreads quickly through vegetation

They create a positive feedback loop: +CO2 in atmosphere → +Radiative heating → +Atmospheric temp → +risk of wildfires → +Atmospheric CO2

Climate change will lead to more intense wildfires

Sudden-onset = Quickly develop (& spread quick)

Conditions required for wildfires

Ignition (e.g. lightning, but could also be human e.g. discarded cigarettes or BBQs)

Adequate atmospheric conditions (Strong winds & low humidity (arid))

Resources to burn (vegetation)

Conditions for intense wildfire

Vegetation Type - Thick close together vegetation allows fire to spread more quickly and easily. Trees and thick bushes lead to more intense wildfires; grasslands don’t burn as intensely. Vegetation with flammable oils like eucalyptus also cause more intense fires. e.g. Chapparal vegetation like sage bush (contain oil/resin promote fire)

Fuel characteristics - Dry vegetation. Finer vegetation = Quicker spread, Thicker larger vegetation = Longer and intense burning

Climate and recent weather - Can occur almost anywhere in the world however strong wildfires only occur in places where there is enough rain for sufficient vegetation but also considerable dry spells and drought to dry out the fuel, e.g. California. Wind also causes fire to spread quicker

Climatic events such as the Santa Ana and Diablo winds in CA can extent and intensify the wildfire season

Case Study: Paradise Wildfire November 2018 (Cause + Impact + Characteristics) CA

Occurred in Butte County (CA)

Faulty hazard perception, partly created by CAL fire (a state agency), people believed they would be protected but the hazard was overpowering

Human cause: PG&E powerlines fault → Spark → Fire

Chaparral vegetation like sage bush (contain oil/resin & dry promote fire)

50,000 fled - Difficult as little roads in and out of the county

Topography - Hills - Travelled 80 football pitches a minute (fire usually spreads faster uphill than downhill)

85 dead

30,000 homeless

Hadn’t rained for 8 months prior to this event

Generally this area has a longer Summer and drier autumn (perfect conditions)

Difficult for planes to put fire out due to intense winds , fighting the fire from the ground was pretty much the only option