1C - Hazards Flashcards
Hazard
a potential threat to human life and property caused by an event.
Degg’s Model
Shows the interaction between hazards, disaster and human vulnerability
What are the 3 major types of Geographical hazard?
Geophysical, Atmospheric, Hydrological
What 5 factors affect hazard perception?
Wealth (Wealthier people may perceive a hazard to be smaller as they are less vulnerable. but they also have more to lose so might see it as a greater risk),
Experience (Someone who has experienced more hazards may be more likely to understand the full effects of a hazard),
Education (A person who is more educated about hazards may understand their full effects on people and how devastating they can be and have been in the past)
Religion and beliefs (Some may view hazards as put there by God for a reason, or being part of the natural cycle of life, so may not perceive them to be negative)
Mobility (Those who have limited access to escape a hazard may perceive hazards to be greater threats than they are.)
What are the human active responses to hazards?
Prediction, Adaptation, Mitigation, Management, Risk Sharing
What is the human passive response to hazards?
Fatalism
What aspect of hazards affects human responses?
Incidence, Distribution, intensity, magnitude, level of development
How does incidence affect human responses to hazards?
Frequency of a hazard.
This is not affected by the strength of a hazard; it is just how often a hazard occurs.
Low incidence hazards may be harder to predict and have less management strategies put in place, meaning the hazard could be more catastrophic when it does eventually occur.
Also, low incidence hazards are usually (but not always) more intense than high incidence hazards.
How does distribution affect human responses to hazards?
Where 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.
How does intensity affect human responses to hazards?
The power of a hazard i.e. how strong it is and how damaging the effects are
High magnitude, high intensity hazards will have worse effects, meaning they will require more management, e.g. more mitigation strategies will be needed to lessen the effects and ensure a relatively normal life can be carried out after the hazard.
Intensity is the effects on the person, and can change dependent on the distance from the hazard or the management strategies combating high magnitude risks.
How does magnitude affect human responses to hazards?
The size of the hazard, usually this is how a hazard’s intensity is measured
High magnitude, high intensity hazards will have worse effects, meaning they will require more management, e.g. more mitigation strategies will be needed to lessen the effects and ensure a relatively normal life can be carried out after the hazard.
Magnitude and intensity are not interchangeable terms
The magnitude is usually definable and can be a number - this does not change.
How does level of development affect human responses to hazards?
Economic development will affect how a place can respond to a hazard, so a hazard of the same magnitude may have very different effects in two places of contrasting levels of development.
an area with a lower level of development is less likely to have effective mitigation strategies as these are costly
However, there are many high income countries that are not as prepared for natural hazards as they should be, meaning they lack the management strategies for an event
Structure of the Earth
inner core, outer core, mantle (asthenosphere, lithosphere) crust
Inner core
A dense sphere of solid iron and nickel at the centre of Earth
Very hot due to pressure and radioactive decay (contains elements such as uranium that give off heat when they decompose)
This heat is responsible for Earth’s internal energy, and it spreads throughout
Outer core
Semi-molten
Iron/nickel
Mantle
Mainly solid rock, and the rocks are high in silicon.
However, the very top layer of the mantle is semi-molten magma, which is known as the asthenosphere.
The lithosphere rests on top.
Asthenosphere
The soft layer of the mantle on which the lithosphere floats.
Semi-molten layer constantly moves due to flows of heat called convection currents. Movements are powered by heat from core.
Evidence for tectonic movement
Continental fit, Mountain ranges, Fossils, use of modern technology
Continental fit
Wegener used evidence like the coast lines appearing to match as evidence of continental drift
Disputed by scientists at the time as they mentioned that coastlines were formed through processes of erosion and deposition
using modern day technology we are able to see that although the coastlines of the continents might not fit perfectly, the deeper crusts around them that don’t experience erosion and deposition do
Mountain ranges (evidence for tectonic movement)
The mountain ranges and rock sequences on opposite sides of the Atlantic also contain a huge number of similarities.
The Caledonian Mountains can be traced from North America through Greenland, Ireland, Scotland and Scandinavia.
These mountains are all of the same age, structure and rock type meaning they must have been part of the same mountain range at some point hundreds of millions of years ago.
Fossils (evidence for tectonic movement)
Glossopteris Flora fossils have been found on all Gondwana continents and the seeds are too large to be carried by wind - must have been carried by land animals.
Present day climates of these continents are too diverse to all support life of this plant.
Use of modern technology
Paleomagnetism, is the remnant magnetism in ancient rock which record the direction and intensity of the Earth’s magnetic field at the time of the rock’s formation
Is evidence of sea floor spreading
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.
Each time these switch the new rocks being formed at plate boundaries align in the opposite direction to the older rock.
On the ocean floor either side of constructive plate boundaries, Geologists observed that there are symmetrical bands of rock with alternating bands of magnetic polarity.
Different types of plate boundary
Destructive, Constructive, Conservative
Destructive plate boundary landforms
Ocean trench, fold mountains, composite volcanoes, island arcs (Oceanic-oceanic)
Constructive plate boundary landforms
rift valleys, shield volcanoes
ridge push and slab pull
the process in which new material at a ridge or rift pushes older material aside, moving the tectonic plates away from the ridge
Hotspots
Hotspots are areas of volcanic activity that are not related to plate boundaries.
What are the 8 volcanic hazards?
lava flows, volcanic ash, pyroclastic flows, mudflows/lahars, glacial floods, tephra, toxic gases, acid rain
lava flow
lava can flow quickly or slowly depending on its viscosity.
Silica makes lava viscous and slow, which is common in explosive eruptions.
lahars (mudflows)
Large amounts of material that become saturated with water and move downslope.
Caused by a number of reasons, usually by melting ice at high latitudes
Glacial floods
When temperatures are high from magma, glaciers or ice sheets at high temperatures quickly melt and a large amount of water is discharged
Tephra
Any type of rock that is ejected by a volcano
Toxic gases
Released during some eruptions, even CO₂ can be toxic as it can replace oxygen as it is heavier
Acid rain
Caused when gases such as sulfur dioxide are released into the atmosphere
pyroclastic flow
Clouds of burning hot ash and gas that collapses down a volcano at high speeds. Average speeds of around 60 mph but can reach 430 mph.
Ring of Fire
A major belt of volcanoes that rims the Pacific Ocean
Vulcanicity (magnitude)
Vulcanicity is measured using the Volcanic Explosivity Index(VEI).
The more powerful, the more explosive.
The scale is logarithmic from VEI 2 and onwards.
Multiple features are considered when calculating the VEI, including how much tephra is erupted, how long it lasts, how high the tephra is ejected etc.
Intense high magnitude eruptions are explosive whereas calmer, lower magnitude eruptions are effusive.
Frequency of Eruption
Frequency of eruptions varies per volcano.
Volcanoes are classed as either active, dormant or extinct.
An estimated 50-60 volcanoes erupt each month, meaning volcanic eruptions are always frequent (and some volcanoes erupt constantly).
Usually, a higher frequency eruption means the eruptions are effusive whereas low frequency means the eruptions are explosive.
Regularity of eruptions
Volcanic eruptions are regular in that the eruptions on each type of boundary are similar (e.g. eruptions on destructive boundaries will regularly be explosive)
Sometimes eruptions may be irregular and not fit patterns
Predictability of eruptions
Regularity of eruptions can help estimate when eruptions will take place (i.e. every 10 years).
Seismic activity, gases releasing, elevation etc. can all indicate an imminent eruption, but there is no definite predictions to a volcanic eruption
Primary, environmental volcanic hazard effects
Ecosystems damaged through various volcanic hazards
Wildlife killed
Secondary environmental volcanic hazard effects
Water acidified by acid rain
Volcanic gases contribute to greenhouse effect (global warming)
Primary, economic volcanic hazard effects
Businesses and industries destroyed or disrupted
Secondary economic volcanic hazard effects
Jobs lost
Profit from tourism industry
Primary, social volcanic hazard effects
People killed
Homes destroyed from lava/pyroclastic flows
Secondary social volcanic hazard effects
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Fires can start which puts lives at risk
Mudflows or floods
Trauma
Homelessness
Primary, political volcanic hazard effects
Government buildings and other important areas destroyed or disrupted
Secondary, political volcanic hazard effects
Conflicts concerning government response, food shortages, insurance etc.
How can volcanic hazards be prevented?
They can’t.
Only the risk to people can be prevented by not allowing people near volcanic hazards (e.g. preventing building around volcanoes
How can we prepare for volcanic hazards?
Monitoring increases the notice of volcanic eruptions, meaning warnings can be given out.
Education on volcanoes in areas of risk so people know what to do if there is an eruption
Evacuation procedures planned
training response teams
How can we mitigate volcanic hazards?
Direct intervention to the volcano, E.g. Concrete blocks to steer lava away from areas at risk
Strengthening buildings that are at risk of mudflows or ash pileup
Evacuation and exclusion zones.
Mitigating effects on health by having emergency aid and rescue.
How can we adapt to volcanic hazards?
Relocate
Capitalise on opportunities such as encouraging tourism
Change profession so it is less likely to be affected by volcanic hazards
What is a tropical storm?
A low pressure, spinning storm with high winds and torrential rain
What conditions are required for a tropical storm to develop?
Ocean temperatures around 26-27°C
Ocean at least 50m deep (warm water provides storm with energy)
Must be in areas with unstable air pressure ( usually where areas of high pressure meet areas of low pressure - convergence)
Wind shear must be perfect - there has to be enough wind present for the swirling motion to form but not too strong otherwise the storm will be ripped apart in early stages.
Can’t form any less than 5° on either side of the equator because there is no Coriolis Effect at the equator.
Needs a trigger (a pre-existing thunderstorm, a spot of very high sea-surface temperature, an area of low pressure etc.)
Stages of formation of a tropical storm
- Warm, moist air rises, leaving an area of low pressure below. This causes warm air from surrounding areas of higher pressure to move into this low pressure area and rise too.
- The warm air condenses into thunderstorm clouds
- The whole system is spinning due to the Coriolis effect (S. Hemisphere storms spin clockwise, N. Hemisphere they spin anti-clockwise)
- The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds. At 39 mph the storm can be classed as a tropical storm.
- The eye of the storm is in the centre. This is an area spanning around 30 miles wide that is of extremely low pressure.
- Surrounding the eye is the eyewall, the most intense and powerful area of the storm. Warm, moist air rapidly rises here, with extremely high winds and torrential rain. When winds reach 74 mph, it becomes a hurricane/cyclone/typhoon.
- When the tropical storm reaches a coast, the low pressure and high winds will cause a large amount of sea water to be taken into the system and then released as a high wave called a storm surge.
- When the storm reaches land, it no longer has a supply of energy and the eye eventually collapses. Heavy rain can persist for days.
Tropical storm magnitude
Measured on the Saffir-Simpson Scale (A scale of 1-5) based on wind speed and thus power of the storm
Tropical storm frequency
Tropical storms form in the Northern Hemisphere from June-November, and the Southern Hemisphere from November-April.
The majority of tropical storms do not develop into strong storms and do not reach land.
Tropical storms that are higher magnitude and reaching land are thought to be increasing in frequency
Tropical storm regularity
Tropical storms are irregular because although they occur in the same areas, their path does not follow a set route - the route taken is dependent on the storm and the climatic conditions.
Tropical storm predictability
Tropical storms form away from land meaning satellite tracking of cloud formations and movement can be tracked and the general route can be predicted.
The closer the hurricane gets, the easier it is to predict. Storm surges can also be predicted based on the pressure and intensity of the storm.
Hazards caused by tropical storms
High winds: over 300km/h and therefore very strong
Flooding: coastal/river flooding from storm surges and heavy rain
Landslides: due to soil becoming heavy when wet with high levels of rain
Storm surges: Large rise in sea levels caused by low pressure and high winds, pushing water towards the coast
Primary environmental effects caused by tropical storms
Beaches eroded
Sand displaced
Coastal habitats such as coral reefs are destroyed
Secondary environmental effects caused by tropical storms
River flooding/ salt water contamination
Animals displaced from flooding e.g. alligators
Water sources changing course from blockages
Primary economic effects caused by tropical storms
Businesses destroyed
Agricultural land damaged
Secondary economic effects caused by tropical storms
Rebuilding and insurance payout
Sources of income lost
Economic decline from sources of income destroyed
Primary social effects caused by tropical storms
Drowning
Debris carried by high winds can injure or kill
Buildings destroyed
Secondary social effects caused by tropical storms
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Homelessness
Polluted water supplies spread disease
Food shortages from damaged land
Primary political effects caused by tropical storms
Government buildings destroyed
Secondary political effects caused by tropical storms
Issues paying back international aid
Pressure for government to do more about global warming
How can tropical storm hazards be prevented?
They can’t really be avoided.
Strategies to mitigate climate change could prevent higher category storms
How can tropical storm hazards be prepared for?
4
Awareness through education of what to do during a tropical storm
Evacuation plans and training
Satellite image tracking to manage the areas that are at risk
Storm warning systems and television broadcasts tracking storm
How can tropical storm hazards be mitigated?
Search and rescue, immediate emergency aid, evacuation (short-term)
Strengthening the home through door barricades, roof strengthening etc.
Clearing loose debris before storms
How can we adapt to tropical storm hazards?
Relocate
Design buildings to withstand high winds and flood damage
Flood defences such as houses on stilts, coastal walls etc.
What causes seismic hazards?
Plates do not perfectly fit into each other - don’t move in fluid motions - plates can become stuck due to the friction between them
When stuck, the convection currents in the asthenosphere continue to push - builds the pressure.
It builds so much that it cannot be sustained and the plates eventually give way.
All of this pressure is released in a sudden movement, causing a jolting motion in the plates.
This jolt is responsible for seismic movement spreading throughout the ground in the form of seismic waves (or shock waves).
What is the focus of a seismic hazard?
The focus is the point underground where the earthquake originates from
What is the epicentre of a seismic hazard?
The epicentre is the area above ground that is directly above the focus.
Distribution of seismic hazards
The Ring of Fire accounts for 90% of the world’s Earthquakes (shown in the
diagram as the Circum-Pacific belt).
The Alpine-Himalayan belt accounts for 5-6% of the world’s earthquakes
Measuring magnitude of seismic hazards
Seismicity is measured using the logarithmic Richter Scale which is a measure of the strength of seismic waves.
The Modified Mercalli Intensity Scale is also used, which is a rate of the destruction caused.
Unlike the Richter scale, the Mercalli scale has a definite end at 12 (XII as it is in roman numerals). The Mercalli scale is subjective, meaning sometimes it is disputed as it is dependent on human development being present rather than the strength of the seismic wave
What affects the magnitude of seismic hazards?
The magnitude of the earthquake is also dependent on the depth of focus.
Conservative boundaries have the shallowest boundaries, meaning they are
closer to the epicentre and the seismic waves are stronger.
Destructive
boundaries usually have deeper focuses, meaning the seismic waves are spread
over a larger area before they reach the epicentre. This is dependent on the
earthquake.
Frequency of seismic hazards?
Earthquakes are frequent around the world and occur every day at boundaries.
Hundreds of smaller magnitude earthquakes that cannot be felt by humans occur every day, whereas the larger earthquakes are less frequent.
Regularity of seismic hazards
Earthquakes follow no pattern and are random so there is irregularity between
events.
Predictability of seismic hazards
Earthquakes are almost impossible to predict.
Microquakes may give some indication but the magnitude cannot be predicted, because how strong they are is random
Hazards caused by seismic events
Shockwaves, Tsunamis, Liquefaction, Landslides and Avalanches
How are shockwaves formed?
When two plates move side by side, friction builds up and pressure increases; this pressure is stored as potential energy, it cannot move so it just builds up.
When the pressure becomes too much, the plates eventually move.
All of the energy that has been built up must go somewhere, so it is transferred into kinetic energy, which is released and vibrates throughout the ground.
The further away from the focus, the weaker the shockwaves, as the energy is transferred into the surroundings.
How are tsunamis formed?
When an oceanic crust is jolted during an earthquake, all of the water above this plate 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 10 feet high, but can reach 100 feet.
How is Liquefaction created?
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 large weight on it
How are landslides and avalanches seismic hazards?
Movement in soil or snow will cause it to become unstable
Primary environmental effects of a seismic hazard
Earthquake can cause fault lines which destroy the environment
Liquefaction
Secondary environmental effects of a seismic hazard
Radioactive materials and other dangerous substances leaked from power plants
Saltwater from tsunamis flood freshwater ecosystems
Soil salinisation
Primary economic effects of a seismic hazard
Businesses destroyed
Secondary economic effects of a seismic hazard
Economic decline as businesses are destroyed (tax breaks etc.)
High cost of rebuilding and insurance payout
Sources of income lost
Primary social effects of a seismic hazard
Buildings collapse, killing/injuring people and trapping them.
Secondary social effects of a seismic hazard
Gas pipes rupture, starting fires which can kill
Water supplies are contaminated as pipes burst, spreading disease and causing floods
Tsunamis which lead to damaging flooding
Primary political effects of a seismic hazard
Government buildings destroyed
Secondary political effects of a seismic hazard
Political unrest from food shortages or water shortages
Borrowing money for international aid
Can be initial chaos and ‘lawlessness’ e.g. looting
How can seismic hazards be prevented?
Majority of seismic hazards can’t be prevented
Liquefaction of soils can be prevented through soil stabilisation - gravel columns can be put in the ground
Avalanches can be prevented through controlled explosions
How can seismic hazards be prepared for?
Extensive awareness strategies and education
Earthquake and tsunami warning systems
Evacuation plans and training
How can seismic hazards be mitigated?
3
Search and rescue, immediate emergency aid, evacuation
Demolishing older, unsafe buildings
Tsunami wave breaks and sea walls
How can we adapt to seismic hazards?
5
Move away from the area at risk
Capitalise on opportunities such as encouraging tourism - San Andreas fault line
Insurance
Changing lifestyle - moving valuable items so they won’t fall
Building specially designed ‘earthquake proof’ buildings
What does the term ‘fatalism’ mean?
The belief that hazards are uncontrollable, so any losses should be accepted and mitigation is unnecessary
