Hazards Flashcards
Define disaster.
A major hazard that causes widespread disruption to a community that may be unable to deal with the impacts without outside help.
Define hazard
A threat that has a potential to cause loss of life, livelihoods or socio-economic disruption.
Define hazard event
Occurrence of a hazard, the effects which cause demographic, economic, or environment changes.
Define hazard risk
The likelihood of a hazard causing harmful consequences.
Define risk
Probability and quantity caused by hazards that present threats to people.
Define fatalism
People choosing to accept the hazards will occur e.g. ‘God’s Plan’. There’s nothing one can do.
Define adaptive
People believe they can be prepared and survive hazards, very dependent on level of development.
Define the Hazard Management Cycle
Cyclical method of preparing for each disaster, focusing on before and after the hazard. Involved hazard identification, analysis of risks, prioritising greatest risks.
Implementing plans, public awareness and monitoring. After an event, infrastructure is repaired and the cycle repeats.
What are the three P’s for disaster management?
Predict - The Risk
Prevent - Mitigate
Protect - People and Property
What are some advantages of the hazard management cycle?
- Focuses on before the hazard.
- Easy to understand.
- Useful to assess pros and cons, what happened vs what should’ve happened.
- Can be applied to any hazard.
What are some disadvantages of the hazard management cycle?
- Certain sections of the cycle are vague.
- Favours HICs who have time, money, resources, and knowledge.
Define Park’s Curve
Shows how a country might respond to a hazard after it has occurred. Often used to understand resilience and preparation for future events.
How thick is the mantle?
2900km
What are the chemical layers within the mantle?
- Lithosphere.
- Asthenosphere.
- Mesosphere.D
Define lithosphere
Made of crust and solid upper mantle.
Define asthenosphere
Layer of upper mantle ductile, can move/reshape slowly.
Define mesosphere
More viscous because it is under pressure. Heat transferred unevenly, leading to plumes and hotspots.
How hot is the core of the Earth?
Around 5000 degrees c.
How does the core create the Earth’s magnetic field?
Core is mostly made of iron and nickel - these are magnetic. The outer core is also liquid which spins and creates the field.
What evidence is there to support the movement of tectonic plates?
- Jigsaw theory = Africa and South Africa ‘fit’ together.
- Similar fossils found on different continents.
- Coal found in Antarctica despite needing warm, wet conditions to form.
- Glacial deposits in Brazil that match Western Africa.
Who initially proposed Continental Drift and when?
Alfred Wegener in 1912.
Who discovered evidence for sea floor spreading in 1962 and what was it?
Harry Hess - Newer rocks were discovered in Iceland and older ones were located on shores of Caribbean and USA.
What method was used to confirm sea floor spreading?
Palaeomagnetism - The study of Earth’s magnetic field.
Define convection currents
Radioactive decay of isotopes create large temperatures. Hot air rises and forces plates away from each other before sinking. Not the driving force of plate movement!
Define ridge push
Lithosphere thickens with time and distance from mid ocean ridge. Boundary between lithosphere and asthenosphere becomes deeper and slopes away from ridge. Gravity acting on weight of lithosphere causes it to slide away.
Define slab pull
When an oceanic plate becomes so dense, it subducts under its weight and pulls rest of plate along with it.
Which plate boundaries do volcanoes occur at?
Converging - lots of volcanoes.
Diverging - less volcanoes but present.
- Transform - NO volcanoes.
Why are there lots of volcanoes in Hawaii?
Hotspot under Hawaii doesn’t move, but plate above does, so volcanoes become extinct when they move away and new islands form.
How does the silica content of lava determine explosivity?
Low silica content means low viscosity meaning less trapped gases. This leads to less explosive eruptions.
Name the three types of lava in order of silica content (lowest to highest)
Basaltic
Andesitic
Rhyolitic
What is another name for nuees ardentes?
Pyroclastic flows.
What are the different types of volcanoes?
- Acid dome
- Caldera
- Ash and cinder
- Shield
- Stratovolcano
How can volcanic eruptions be predicted?
- Seismicity weeks and days beforehand may be unusual.
- Tiltmeters measure the ground.
- Changing magnetism is an indicator.
- Rising magma heats groundwater.
- Measuring sulphur dioxide levels.
What is the proportion of earthquakes occurring at plate boundaries?
95% - 80% occur at Ring of Fire.
What are the three foci of earthquakes?
Shallow focus (0-70km)
Intermediate focus (70-300km)
Deep focus (300-700km)
Define the Benioff Zone
100-700km below Earth’s surface. Source of medium and deep focus earthquakes.
Define P-waves
Primary Body Wave - Fastest and reach surface first. Have a high frequency. Travel through mantle at 6km/s and core at 13km/s.
Define S-waves
Secondary Body Wave - High frequency, shake like a skipping rope. Travel through mantle at 3.5km/s but NOT the core.
Define L-waves
Love Surface Waves - Slowest but cause most damage. Move side to side and originate from epicentre. Only travel through lithosphere.
Define R-waves
Rayleigh Surface Waves - Radiate from epicentre in complicated patterns. Move at 0.34km/s.
Define liquefaction
Soil saturated with water, earthquake vibrations can cause it to act like a liquid. Soil becomes weaker and deforms/subsides. More likely when something heavy is on top of it.
What are the three scales for measuring earthquakes?
Richter scale
Mercalli scale
Moment magnitude scale
Define the mercalli scale
Intesnity of damage is recorded through observations on the ground, from: I - Imperceptible to XII - Catastrophic.
Define the Moment Magnitude Scale (MMS)
Scale similar to Richter scale, based on total energy released by earthquake. More accurate than Richter scale.
What are ways to predict earthquakes?
Earthquakes are hard to predict due to their chaotic nature.
What are some ways to plan for an earthquake?
- Procedures put in place.
- Building design made to stop total collapse.
- Resistance of forces, diagonal bracing, rigid girders.
- Absorbing the sway, taller buildings designed to sway in the shaking.
- Flexible piping to reduce damage and fires.
Define high pressure
Cool, dry, sinking air. Leads to clear skies and no precipitation. Often in hot and cold deserts.
Define low pressure
Warm, wet, rising air. Cools and condenses to form precipitation as rain/sleet/snow. Often in tropical rainforests.
What is the Coriolis effect?
The spin of the Earth which is strong enough to rotate tropical storms.
Why don’t tropical storms occur at high latitudes?
Coriolis effect is too strong and sea temperatures do not reach 26.5 degrees.
Define tropical storms
An intense, low pressure weather system that develops in the intertropical convergence zone. Around 200-700km in diameter and winds of 74mph.
Define convectional rainfall
Rain in warm, wet conditions. Water evaporates and condenses very quickly, short, heavy bursts of rain.
Define frontal rainfall
Occurs when warm air meets cold. Warm air less dense so rises above cold air, air then condenses and falls as precipitation.
Define relief rainfall
Mass of air rises over a mountain and cannot get over the entire mountain. Rain condenses and falls at the dew point.
What is the fire triangle?
- Heat source.
- Oxygen.
- Fuel
NO fire occurs if one isn’t present.
What % of wildfires are caused by human activity?
90%
What are the main causes of human induced wildfires?
- Campfires burning out of control.
- Cigarettes.
- Arson.
What are the benefits of wildfires?
- Remvoe harmful insects or diseased plants.
- Allows sunlight to reach forest floor.
- Ash fertilises the soil.
What are the three layers to a wildfire?
- Crown fires
- Surface fires
- Ground fires
Define a crown fire
Fire that burns in forest canopies with large flames. Most intense heat and most difficult to control.
Define a surface fire
Fire that burns across surface vegetation at around 900 degrees c. Easiest to control.
Define a ground fire
Fire that burns in dry, peat layers underground. Burn for the longest time, meaning new fires can occur in already burnt areas.
What are three ways that fires can spread?
- Spotting = Winds blow embers from crown fires.
- Firebrands = Fireballs flying from burning trees to new areas.
- Conflagration = Large fires increase intensity with their own wind patterns and firebrands.
What are the natural causes of wildfires?
- El Nino.
- Drought.
- Dry lightning strikes (no rain to put it out).
What factors impact the rate of fire spread?
- Fuel.
- Topography
- Temperature and humidity
- Climatic conditions
How does fuel increase rate of wildfire spread?
- Flammable oil in trees.
- High moisture content in trees slows burning.
- Greater fuel density increases rate of burning.
How does topography affect the rate of wildfire spread?
- Heat and smoke rises
- Rising heat warms fuel uphill.
- Stronger winds = longer, narrower fires.
- Steeper gradient leads to faster spread uphill, but slower downhill.
How does temperature and humidity affect the rate of wildfire spread?
- Higher temperatures lead to moisture being absorbed.
- If humidity is higher than 15%, risk is lowered.
- If humidity is lower than 7%, risk is raised.
- Early afternoon is hottest part of day, greatest risk of fire.
How do climatic conditions affect rate of wildfire spread?
- Winds can change direction of fire.
- Fire tornadoes throw flaming debris.
- El Nino can cause warmer than average temperatures and drought for extended periods of time in wildfire prone areas.
Define pyrophytic vegetation
Plants adapted to tolerate fire through thick bark tissue and higher moisture content.
What are fire retardants?
Chemicals sprayed on wildfires to slow them down. Usually made of nitrates, ammonia, phosphates, sulphates, and thickening agents.
How have sequoia trees adapted to wildfires?
Have spongy bark to insulate from heat energy and branches don’t start until they are above the flames of most fires.
What is the ladder effect?
The process by which wildfires go from ground fires to crown fires.
What are some features of specialised wildfire engines?
- Equipment can spray water and foam.
- Can hold up to 800 gallons of water.
- Equipped with 4 wheel drive.
What are smokejumpers?
People that jump from planes into cut off areas from wildfires. Typically carry axes and gel to create small firebreaks and slow advances of fire.
What are control lines?
Areas that have fuel removed. They take lots of people but can slow the fire if not stop it.
What is backfiring and why is it dangerous?
Backfiring deliberately burns up areas of land, using up the fuel for fire. Bulldozers are sometimes used. However, these can start new wildfires.
Define GIS and its use in wildfires
Geographical Information Systems.
Developed to show wildfire extent. Can also use ‘layers’ to show areas of rainfall variability, fuel availability etc.
What is a multi-hazardous environment?
An area that experiences two or more hazards, often with large concentrations of vulnerable people.
Define the HDI
Human Development Index - A measure of achievements in a country with three indicators: Health, knowledge, and standard of living.
What is bilateral aid?
Aid that is given by a country with requirements that money is spent on goods and services that benefit the donor country.
What is multilateral aid?
High income countries that donate money through organisations and the World Bank.
What are levees?
An embankment built to prevent the overflow of a river or the sea.
What is an equal opportunity storm?
People are treated the same way regarding the storm and recovery, no discrimination. Not seen in New Orleans.
