Hazards Flashcards
What are the three types of natural hazard?
Geophysical
Atmospheric
Hydrological
What types of natural hazard are atmospheric?
Tropical storms
Droughts
Tornadoes
Can be monitored. Warnings can be given.
What types of natural hazard are geophysical?
Volcanic hazards
Seismic hazards
Can be monitored but accurate prediction is difficult
What types of natural hazard are hydrological?
Those that involve flooding and relate to the hydrosphere
Can be monitored. Warnings can be given.
What types of natural hazard are hydrological?
Those that involve flooding and relate to the hydrosphere
Can be monitored. Warnings can be given.
What is the difference between a hazard and a disaster?
A hazard is a potential threat to human life or property; a disaster is a hazard that seriously affects humans, exceeding a threshold level.
What factors can influence people’s perception of hazards?
Wealth (richer = more able to move)
Religion (hazards act of God to punish people)
Education
Past experience
Personality
What are some characteristic human responses to hazards?
Fatalism
Prediction
Adaption
Mitigation
Management
Risk sharing
What factors can affect the success of attempts to manage hazards?
Hazard incidence (how often)
Magnitude
Intensity
Distribution
Level of development
What is the Park Model?
A model that shows how responses progress invented in 1991. Also called the Disaster Response Curve.
Why is the Park Model useful?
Helps planners predict what resources needed for each stage.
Preparation for future hazard events.
What are the five stages on the Park Model?
Pre-disaster (before)
Disruption (during)
Relief (rescue)
Rehabilitation (resolve longer term)
Reconstruction (rebuilding and improving)
What is the Hazard Management Cycle?
The four stages authorities go through in managing hazards.
What are the four stages in the Hazard Management Cycle?
Mitigation (minimise impact)
Preparedness (planning)
Response (reaction)
Recovery (returning to normal)
What are the benefits of the Park Model?
Compare significance with normality
Chart stages
Indicate magnitude/severity
Compare two events
Help understand preparedness of community
What are the benefits of the Hazard Management Cycle?
Take into account steps taken before a hazard to mitigate
Considers how one hazard lead into the next
Helps chart stages
What are the limitations of the Park Model?
Doesn’t specify steps taken before event
No quantitative data
Doesn’t consider complexity of secondary impacts
No account for spatial variation
Overly simplistic
What are the limitations of the Hazard Management Cycle?
No indication of time scale
No quantitative data
Doesn’t consider complexity of secondary impacts
No account for spatial variation
Overly simplistic
What are the three main layers of the Earth?
Crust
Mantle
Core
What minerals does the Earth’s inner core contain?
Solid iron and nickel
What minerals does the Earth’s outer core contain?
Semi-molten iron and nickel
How thick is the Earth’s inner core?
1200 km
How thick is the Earth’s outer core?
2400 km
What temperature is the Earth’s inner core?
6000 Degrees Celsius
What temperature is the Earth’s outer core?
4,400 Degrees Celsius
How thick is the Earth’s mantle?
3,000 km
What temperature is the Earth’s mantle?
1,000 - 5,000 Degrees Celsius
What minerals make up the Earth’s mantle?
Magnesium
Iron
Silicon
Oxygen
What are the properties of the Earth’s mantle?
Hard
Elastic
Cracks
Ductile
What are the three subdivisions of the Earth’s mantle?
Mesosphere
Asthenosphere
Lithosphere
What are the properties of the mesosphere?
Rigid due to pressure
Closest to the core
What are the properties of the asthenosphere?
Ductile zone
Highly viscous
Mechanically weak
Semi-molten state
What are the properties of the lithosphere?
Furthest from core
Brittle crust / top part of upper mantle
Coolest and most rigid part of the Earth
How thick is the Earth’s crust?
5 - 70 km
1% of Earth’s volume
What is Mohorovicic Discontinuity?
Also called the Moho.
A discrete jump in seismic wave velocities.
How deep is the Moho?
25 - 60 km beneath the continents
5 - 8 km beneath the ocean floor
What was Alfred Wegener’s Continental Drift theory?
Different large landmasses of the Earth (continents) fitted together as Pangaea. They drifted apart over 200 million years.
What geological evidence supports Continental Drift theory?
Good fit of continents.
Similar rock types next to Atlantic Ocean.
Appalachian Mountains North America and mountains in Scotland and Scandinavia has similar age, structure, rock type.
What biological evidence supports Continental Drift theory?
Identical fossils found directly opposite on widely spread continents.
Inc. fossils of creatures who could not swim.
Fossils of both plants and animals.
What climatological evidence supports Continental Drift theory?
Glacial till of same age found in S Africa, S America, India and Australia.
All places where it would be difficult to explain occurrence of glaciation.
What evidence has been put forward to support continental drift theory after the work of Wegener?
The Mid Atlantic Ridge
Sea Floor Spreading
Palaeomagnetism
What is Palaeomagnetism?
Studying the rocks formed by underwater volcanic eruptions in relation to the Earth’s magnetic field.
How do convection currents work?
Lower parts of the asthenosphere heat up, become less dense and rise.
They cool down at the top, become dense and fall.
Friction drags on the base of tectonic plates, moving them.
What is slab pull?
At destructive plate margins, denser crust is forced under less dense crust.
The sinking of the plate edge pulls the rest of the plate towards the boundary.
What is ridge push / gravitational sliding?
Constructive plate margins.
Magma rises to the surface.
Hot new crust.
Surrounding rocks heat and expand. Rise above the surface of surrounding crust forming a slope.
New crust cools, becomes denser, gravity bringing it downslope, away from plate margin.
This puts pressure on the plates moving them apart.
What is seafloor spreading?
Plates diverge.
Magma rises up to fill the gap, then cools to form new crust.
Over time, the new crust is dragged apart and even more new crust forms between it.
The seafloor gets wider.
Creates mid-ocean ridges.
What are the two types of tectonic plate?
Oceanic
Continental
What type of rock makes oceanic plates?
High-density basaltic rock
How thick are oceanic plates?
7 - 10 km
What type of rock makes continental plates?
Less dense granitic rock
How thick are continental plates?
25 - 75 km
What occurs at conservative plate margins?
Plates move past each other.
They lock together.
Pressure and potential energy builds up.
The plates jerk past each other.
Energy released as an earthquake.
E.g. Pacific and North American plates San Andreas fault California.
What occurs at constructive plate margins?
Convection currents diverge two plates.
A gap is created betwixt them.
Magma rises up to fill the gap.
New crust created as the plate pull away.
Rift valleys and ocean ridges can form.
What occurs at destructive plate margins?
A denser plate slides beneath a less dense plate.
Crust is destroyed as one plate dives under another at the subduction zone.
The rocks catch against each other.
Pressures builds until the plates can’t take the stress.
The plates slip past each other, which can cause both plates to move resulting in tremors.
What occurs at continental-oceanic destructive / destructive subduction plate margins?
Denser oceanic plate subducts below the continental.
The plate subducting leaves a deep ocean trench .
Fold mountains occur when sediment is pushed upwards during subduction.
Oceanic crust melted as it subducts into the asthenosphere.
The extra magma created causes pressure to build up.
Pressurised magma forces through weak areas in continental plate
Explosive, high pressure composite volcanoes erupt through continental plate.
What occurs at oceanic-oceanic destructive plate margins?
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.
What occurs at continental-continental destructive /destructive collision plate margins?
Both plates are not as dense as oceanic 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 lithosphere due to pressure between plates.
Fold mountains formed from piles of continental crust.
How are fold mountains formed?
Destructive subduction or destructive collision plate boundaries.
Plates move together, sediment pushed into folds between them.
What is are two good examples of fold mountains?
The Andes mountains. Nazca plate and S. American plate subduction.
Himalayas. Indian Plate and Eurasian Plate collision.
How are island arcs formed?
Destructive subduction boundaries.
Descending plate melts. Material rises towards surface as plutons of magma.
These reach surface forming volcanoes.
These may erupt offshore, causing a line of volcanoes.
What is a good example of an island arc?
The Marianas Island Arc western Pacific Ocean.
Pacific Plate and Philippine Sea Plate
How are deep sea trenches formed?
Destructive subduction plate boundaries.
Oceanic plate subducted under continental plate.
The downwarping of the oceanic plate forms a very deep part of the ocean: a trench.
What is a good example of a deep sea trench?
Peru-Chile trench. Nazca plate and S. American plate.
Marianas trench. Pacific Plate and Philippine Sea Plate.
How are volcanoes formed?
Constructive or destructive subduction plate margins.
Melted plate rises to the surface as magma.
How are ocean ridges formed?
Constructive margins.
Two oceanic plates diverge.
As pressure is reduced, semi-molten magma of mantle melts. Rises up into gap between plates, forming a ridge.
What is a good example of an ocean ridge?
The Mid-Atlantic Ridge.
Between the North American Plate and the Eurasian Plate.
How are rift valleys formed?
Constructive margins.
Two continental plates diverge.
Crust thins and is heated and bulges, forming cracks.
An area of crust drops down between parallel faults.
What is a good example of a rift valley?
East African Rift.
Somalian and Nubian plates.
What is a magma plume?
A vertical column of extra-hot magma that rises up from the mantle.
How do magma plumes form volcanoes?
A magma plume remains stationary over time but crust moves above it.
Volcanic activity in the part of the crust that was above the magma plume decreases as it moves away.
New volcanoes form in the part of the crust that is now above the magma plume.
As the crust continues to move, a chain of volcanoes is formed.
What is a good example of magma plumes that have formed volcanoes?
The chain of islands that makes up Hawaii was formed b a magma plume around 500,000 years ago.
How can a constructive plate margin affect vulcanicity?
Basaltic lava is formed here
Very hot and low viscosity (very runny)
Flows easily and quickly
Frequent eruptions but not violent
How can a destructive plate margin affect vulcanicity?
Andesitic and rhyolitic lava formed here
Cooler and more viscous than basaltic, flows less easily
Intermittent, short-lived eruptions
At subduction zones, melting plate forming magma results in a volcano
The viscous lava can cause blockages, causing pressure
This is cleared by violent eruptions
What are the main primary volcanic hazards?
Pyroclastic flows / nuées ardentes
Lava flows
Volcanic gases
Pyroclastic and ash fallout
What are the main secondary volcanic hazards caused by primary hazards?
Mudflows / lahars
Acid rain
What is hazardous about pyroclastic flow / nuées ardentes?
Plume of hot ash and gas ejected out of a volcano.
Can exceed 1,100°C.
High speeds over 300 km/h.
Flow 10-15 km.
What is hazardous about lava flows?
Rarely cause injury due to relatively low velocity.
Unstoppable; damage crops.
Up to 10 km/h.
Can travel tens of kilometres.
What is hazardous about volcanic gases?
Lava contains gases such as carbon dioxide and sulphur dioxide, released into the atmosphere when a volcano erupts.
Some of these gases can be harmful to humans and animals if breathed in.
What is hazardous about pyroclastic and ash fallout?
Pyroclastic fallout is material that has been ejected from a volcano during eruption and falls back to ground.
When fallout consists mostly of ash it’s ash fallout.
Fallout consists of material of a range of sizes, can travel thousands of kilometres from volcano.
Heavier particles deposited earlier than light ones.
Large pieces of falling tephra can damage buildings and kill and injur people.
What is hazardous about tephra?
It’s solid material of varying grain size ranging from volcanic bombs to ash, all ejected into the atmosphere, potentially causing injury to people.
What is hazardous about mudflows / lahars?
Occur when volcanic material mixes with large amounts of water (from rainfall or melted ice).
Move very quickly (over 80 km/h).
Travel tens of kilometres.
Can bury or destroy natural habitats, settlements and infrastructure).
What is hazardous about acid rain?
Volcanic gases can react with water vapour in the atmosphere, which then falls as acid rain. E.g. sulphur dioxide reacts with water to form weak sulphuric acid.
This can damage ecosystems, and cause stone and metal to deteriorate, damaging buildings, bridges, statues etc.
How can the spatial distribution of volcanic hazards be described?
Along constructive or destructive plate boundaries, or located on hotspots.
The Ring of Fire is an area of high volcanic and earthquake activity located in the Pacific, and the majority of large volcanoes occur within this 25,000 mile belt.
How is the magnitude of vulcanicity measured?
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.
What is the general frequency of volcanic hazards?
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.
What is the general regularity of volcanic hazards?
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.
What is the general predictability of volcanic hazards?
Some volcanoes erupt at very regular intervals, whereas other may be dormant for hundreds or thousands of years then erupt several times in quick succession.
What are the three types of response employed to reduce the impacts of future hazards long term?
Prevention
Preparation
Adaption
What volcano in which LIC erupted in January 2002?
Mt Nyriangongo
Democratic Republic of Congo
What were the primary environmental impacts of the eruption of Mt Nyriangongo?
Lava flows caused fires
Melting runway produced poisonous gases
What were the secondary environmental impacts of the eruption of Mt Nyriangongo?
Rainwater became acidic
What were the primary social impacts of the eruption of Mt Nyriangongo?
80,000 made homeless immediately
Emergency aid couldn’t land at airport
Lava destroyed 14 villages on day one
180 people killed by lava and gases
20% homes destroyed
Power stations exploded
Hospital destroyed
How many people in total died as a result of the eruption of Mt Nyriangongo?
An estimated 250 people
What were the secondary social impacts of the eruption of Mt Nyriangongo?
Parts of Goma buried by up to 3m of lava
Rioting in Goma as food ran out
Refugee camps
400,000 evacuations
Cholera outbreak
What were the primary economic impacts of the eruption of Mt Nyriangongo?
Emergency vehicles buried under lava unable to respond
Airport severely damaged forced to close
What were the secondary economic impacts of the eruption of Mt Nyriangongo?
Widespread unemployment
Local shops closed
Businesses destroyed.
Why do people stay in Goma despite the hazardous volcanic activity?
Nowhere else to go
Fatalism
Geothermal energy
Nearby soil often rich in minerals for farming opportunities
What are scientists trying to do to prepare for future volcanic hazards in DRC?
Seismographic detection
What problems remain in Goma after the eruption of Mt Nyriangongo?
Widespread poverty
Emergency services not up to standard
Lack of satellite technology
Lack of education about volcanoes
Where is Eyjafjallajokull located?
South Iceland, North-West Europe, Atlantic Ocean
What tectonic plate is responsible for the eruption of Mt Nyriangongo?
The African plate which is moving apart.
Which tectonic plates are responsible for the eruption of Eyjafjallajokull?
Eurasian and North American plates
What was the population of DRC?
85 million
What was the population of Iceland?
345,000
What were two secondary economic impacts of the eruption of Eyjafjallajokull?
Increased tourism.
Cancellation of flights all across Europe.