Hazards (Physical) Flashcards
Describe the crust:
The thin layer of the outer shell that we live on, 5-10km thick beneath oceans and 70km thick beneath continents, lithosphere
Describe oceanic plates:
An occasionally broken layer of basaltic rocks known as sima - silicon and magnesium
Describe continental plates:
Bodies of mainly granite rocks, known as sial - silicon and aluminium
What is the lithosphere?
The crust and upper mantle, where tectonic plates are formed
How thick is the mantle?
2900km
What is the asthenosphere?
A layer of soft, plastic like rock that carries the lithosphere
How hot is the core?
5000 degrees C
What are intrusive rocks?
Rocks formed by the cooling of molten Magma, that crystallises and solidifies slowly below the surface. Forms coarse grained igneous rocks. Vertical dykes and inclined sills may form within.
What are extrusive rocks?
Lava that is in contact with the air or sea. It cools, crystallises and solidifies much quicker than Magma that is still underground. Fine grained rocks with small crystals.
What is gravitational sliding?
The movement of tectonic plates under the influence of gravity
What is ridge push?
Gravity acting on the weight of the lithosphere near the ridge pushes the older part of the plate in front.
What is slab pull?
The lithosphere sinks into the mantle under its own weight following subduction, helping to ‘pull’ the rest of the plate with it.
What events and landforms occur at Constructive boundaries?
Volcanoes
Mid ocean ridges
Rift valleys
What events and landforms occur at Destructive boundaries?
Powerful earthquakes
Volcanoes
Fold Mountains
Ocean trenches
What events and landforms occur at Collision boundaries?
Powerful earthquakes
Fold Mountains
What events and landforms occur at Conservative boundaries?
Powerful earthquakes
What is jigsaw fit evidence for tectonic theory (Wegener, 1912)?
Similarity in outlines of West Africa and South America as well as other continental areas. Best fit at 1000m below sea level.
What is geological fit evidence for tectonic theory?
Ancient rock outcrops from South America and West Africa from over 2000 million years ago were continuous
What is Tectonic fit evidence for tectonic theory?
Fragments of the Caledonian mountain belt are found in Scotland, England, Greenland, Canada and Scandinavia
What is glacial deposit evidence for tectonic theory?
300 million year old deposits found in Africa, Australia, Antarctica, South America and India suggest ancient ice sheet
What is fossil evidence for tectonic theory?
Bands of identical fossils lie across continents, particularly of organisms which could not have travelled.
What happens at a conservative boundary?
Two plates do not directly collide but slide past one another
What happens at a constructive boundary?
2 plates are moving apart, leaving a gap for magma to rise up through. Volcanoes form but don’t erupt with force and earthquakes occur
Where are rift valleys common?
Where 3 plates meet at a junction
What happens at destructive boundaries?
Dense oceanic plate descends beneath less dense continental plate. Oceanic plate melted due to friction forming magma
What happens at collision boundaries?
Two plates of similar densities move together, causing the material between them to buckle and rise up
Where do rift valleys form?
On constructive boundaries
How do rift valleys form?
Magma rises and plates move apart
Over a magma chamber, crack and faults appear
Blocks of crust descend into mantle, creating steep sided valleys
Central plateaus sink in the middle, forming lakes
What is a Benioff zone?
The further the rock descends, the hotter it gets. Together with the heat from friction begins to melt the plate to magma
What boundaries do ocean trenches form at?
Destructive
What are the characteristics of shield volcanoes?
Gentle slopes, wide base
Frequent eruptions, basic lava
High speed and low viscosity basaltic lava
Non-violent eruptions
What are the characteristics of composite volcanoes?
Steep sides, cone shape
High with narrow base
Explosive eruptions
Layers of alternating ash and lava
Secondary/parasitic cones
What are the two types of lava?
Pahoehoe (thin) and A’a (thick)
What is a pyroclastic flow?
Fast flowing currents of rock, ash and hot gas from a volcanic eruption
Hot enough to kill in an instant.
What is a lahar?
Violent mudflow or debris caused by melting snow or ice.
What are tephras?
Rock fragments and particles ejected by volcanic eruption
How is vulcanicity measured?
- Volcanic Explosive Index - more powerful = more explosive
How often do volcanoes erupt
- Around 30-60 erupt each month
What hazards are caused by volcanoes?
- Lava flows
- Lahars (mudflows)
- Floods
- Tephra
- Acid Rain
- Toxic Gases
- Pyroclastic Flows
What are the characteristics of shield volcanoes?
Gentle slopes, wide base
Frequent eruptions, basic lava
High speed and low viscosity basaltic lava
Non-violent eruptions
What are the characteristics of composite volcanoes?
Steep sides, cone shape
High with narrow base
Explosive eruptions
Layers of alternating ash and lava
Secondary/parasitic cones
Different responses to hazards [6]
- Fatalism
- Prediction: scientific research can help predict them
- Adaptation: adjusting lifestyle choices to live with hazards
- Mitigation: strategies to reduce the impact of a hazard
- Management
- Risk sharing: community shares the risk imposed by a hazard & prepares collectively
What are the places plates meet called?
Plate margins
What is nuees ardentes?
Pyroclastic flows:
Fast flowing currents of rock, ash and hot gas from a volcanic eruption
Hot enough to kill in an instant.
Hazard Management Cycle
- Outlines the stages of responding to events, showing how the same stages take place after every hazard
Park Model
- Graphical representation of steps taken in hazard recovery
- Provides a rough indication of the time frame
Eyjafjallajokull Spatial and temporal evidence (2)
- April 2010, Iceland volcano erupted -> located on spreading ridge
- Constructive/Divergent plate territory, convection currents
Eyjafjallajokull Effects in Iceland (3)
- Areas flooded due to glacial melt water
- 700-800 evacuated
- Ash quantities poisoned animals, people had to wear masks
Eyjafjallajokull Effects elsewhere (4)
- 100,000 flights disrupted for 10million people between 14-21st April 2010.
- Airlines lost $1.7 billion revenue.
- 50,000 Kenyan farmers laid off as no food transport
- People left stranded, unable to commute
Eyjafjallajokull Tectonic setting (3)
- Small volcano in SE rift zone chain of volcanoes
- Located West of Katla volcano
- Scientists scared it would trigger Katla.
What hazards can earthquakes form?
Tsunamis - caused by displacement of large volumes of water
Landslides/Avalanches - shaking of ground can dislodge rock, soil or snow
Soil Liquefaction - vibrations of an earthquake can make soil saturated with water act like a liquid
What is soil liquefaction? [2]
- When soil is saturated with water, the vibrations of an earthquake can cause it to act like a liquid
- Makes soil weaker & easier to deform, so it’s more likely to subside, especially where it has a heavy weight on top (e.g. a building)
How often to do low magnitude / high magnitude earthquakes occur?
Low magnitude: Every day
High magnitude: much less often
Are earthquakes predictable?
- Currently impossible to tell when an earthquake will strike & magnitude
What are shockwaves? {2}
- When plates jerk past each other it sends out shockwaves.
- These vibrations are the earthquake - spreads out from the focus.
Name 2 social impacts of seismic hazards
- Earthquakes can cause buildings to collapse, killing & injuring people
- Lack of clean water can cause disease to spread
Name 2 environmental impacts of seismic hazards
- Fires started by damaged gas and electricity lines can destroy ecosystems
- Tsunamis can flood freshwater ecosystems, killing plants & animals
Name 2 economic impacts of seismic hazards
- Damage to buildings and infrastructure can be very expensive to repair
- Damage to industry may mean the country has to rely on expensive imports of goods & energy
Name 2 political impacts of seismic hazards
- Shortages of food, water & energy can cause conflict and political unrest
- Governments may have to borrow money for aid, leading to debt
Prevention of seismic hazards [2]
- Not possible to prevent most seismic hazards
- Possible to prevent them posing a risk to people e.g. building giant sea walls to prevent tsunamis
Preparedness against seismic hazards [3]
- Earthquake warning systems e.g. TV & SMS
- Plans for how to respond during an earthquake e.g. evacuation drills
- Search & rescue teams or fire response units can be set up
Adaptation to minimise risks of seismic hazards [2]
- Buildings designed to withstand earthquakes e.g. foundations that absorb an earthquake’s energy
- Designed to reduce vulnerability to tsunamis e.g. strong tall buildings
Short-term responses to seismic hazards [2]
- Rescuing people from collapsed buildings after an earthquake
- Evacuating people from areas at risk from a tsunami
Spatial and temporal setting of Tōhoku Earthquake (3)
- Struck below the North Pacific Ocean, 130km east of Sendai
- Magnitude 9.0 earthquake 11th March 2011
- Located on the ‘ring of fire’ - frequent earthquakes
Perception of Tōhoku Earthquake (3)
- It was unexpected, few scientists predicted it
- “Polite demeanour”, little looting afterwards
- Feb 2017- still 150,000 evacuees who lost homes
Causes of Tōhoku Earthquake (3)
- Along a subduction zone, plates collided and energy released as eq’s
- Pacific plate subducted by Eurasian plate
- Shaking lasted 6 minutes
Impacts of Tōhoku Earthquake (5)
- Killed 15,980 people
- Caused Fukushima power plant meltdown -> EXPLOSIONS, was nearly fatal
- 500,000 left homeless
- $360 billion in damages - the worlds costliest natural disaster
- 353 cultural properties damaged
Responses to the Tōhoku Earthquake (3)
- Tsunami warning sent out 3 min after quake
- 30km evacuation zone from power plant
- FDMA dispatched Emergency Fire Response Teams
What are tropical storms?
Huge spinning storms lasting 7-14 days, with strong winds and torrential rain
Where do tropical storms develop?
Over warm water - as moist air rises and condenses it releases energy that increases wind speed
Occur in Carribbean sea, Bay of Bengal, China Sea & Northern Australia
What are the conditions needed for tropical storms to develop? [3]
- An area of low pressure
- Warm sea water above 27 degrees
- A location at least 5 degrees from the equator
Why do storms move away from the Equator?
The Coriolis effect:
Deflects the path of winds but is weak at the equator
What is storm magnitude measured on?
The Saffir-Simpson scale Category 1 (120km/h winds) Category 5 (>250km/h winds)
How frequent are tropical storms?
Around one hundred occur every year
Northern hemisphere: more frequent June-November
Southern hemisphere: more frequent November-April
Are tropical storms regular?
There are lots of factors affecting where a tropical storm will form so the hazards created by storms are largely irregular.
How can tropical storms be predicted? [2]
- Cloud formations can be identified from satellite imagery & used to tell when a tropical storm is forming.
- Can be tracked using satellite imagery - path of a tropical storm can be predicted accurately
2 Social impacts of tropical storms
- Houses are destroyed, so people are left homeless
- People may drown, be injured or killed by debris/ flood water
2 Political impacts of tropical storms
- Expensive repairs to buildings, infrastructure etc limit amount of money that can be spent on development
- People may blame authorities for food, water & energy shortages -> conflict & political unrest
2 Economic impacts of tropical storms
- Buildings & infrastructure cost a huge amount to rebuild
- Agricultural land is damaged, affecting commercial farming
2 Environmental impacts of tropical storms
- Beaches are eroded and coastal habitats are damaged
- Environments are polluted e.g. by salt water
Short term responses to tropical storms [2]
- Occur immediately before, during or immediately after the hazard
- Evacuating people from areas of risk
Prevention of tropical storms
- Can’t be prevented but future developments can be planned to avoid high risk areas
Preparedness for tropical storms [3]
- Emergency services can train & prepare for disasters
- Governments can plan evacuation routes
- Educating people on how to prepare for a storm
Adaptation against tropical storms [2]
- Buildings can be designed to withstand tropical storms e.g. reinforced concrete
- Flood defences e.g. levees can be built along rivers & coasts e.g. sea walls.
[HURRICANE KATRINA 2005] When did Katrina occur?
23-31st August 2005
Began in Bahamas
[HURRICANE KATRINA 2005] Which area did Katrina damage most?
New Orleans, on gulf coast of USA
[HURRICANE KATRINA 2005] Why was New Orleans vulnerable? [4]
- Levee system failed
- Location
- People didn’t leave- fatalism
- Severity of storm
[HURRICANE KATRINA 2005] Winds
Reached 175mph
[HURRICANE KATRINA 2005] Why did levee system fail?
- Not been constructed to modern standards.
- The severity of storm also to blame
- After 24 hours 80% of area was underwater
[HURRICANE KATRINA 2005] How was New Orleans represented in media? [2]
As a disaster waiting to happen
Bureaucracy slows down relief effort
[HURRICANE KATRINA 2005] Why did the aftermath of storm cause more devastation? [2]
Lack of leadership.
Evacuation was only initiated 19 hrs before landfall.
[HURRICANE KATRINA 2005] How many DIDNT evacuate?
130,000
[HURRICANE KATRINA 2005] Social primary [3]
60,000 people were stranded in New Orleans.
The Coast guard rescued 33,500 people
Most people fled in private cars and school buses
[HURRICANE KATRINA 2005] Primary economic [2]
Transported destroyed
Flyovers collapses from flooding and pressure
[HURRICANE KATRINA 2005] Environmental primary [2]
Water polluted with sewage and oils
Crops / habitats destroyed
[HURRICANE KATRINA 2005] Secondary social [3]
Looting
1 million refugees traumatised
Racial tensions, many people were African Americans
[HURRICANE KATRINA 2005] Secondary economic [3]
Destroyed 30 oil platforms
Tourism reduced
Financial cost $200 billion
[HURRICANE KATRINA 2005] Secondary environmental [3]
- 16 national wildlife refugees closed.
- Breeding grounds for marine mammals lost.
- Flooding - 110,000 out of 180,000 houses
[HURRICANE KATRINA 2005] Immediate responses [3]
- Management aid came from USA internal federal aid.
- Volunteers gave assistance.
- Approx 58,000 national guard personnel were activated to deal with storms aftermaths troops from 50 states
[CYCLONE NARGIS 2008] Why was the Government ineffective? [4]
- Refused aid, politicizing the aid, leaving Burma with a lack of aid
- Military junta gov.
- 100,000 ppl killed
- Low rations
[CYCLONE NARGIS 2008] When was Cyclone Nargis?
25th April 2008- 4th May
Name & explain the three types of wildfires [3]
Ground fire: The ground itself (e.g. peat & tree roots) burns, slow smouldering fire
Surface fire: Leaf litter & low-lying vegetation burn. Fire can be low or high intensity
Crown fire: where fire moves rapidly through canopy (top layer of vegetation)
How can vegetation type affect wildfire intensity? [2]
- Closely spaced trees in contrast to patchwork forests allow fire to travel easily
- Eucalyptus trees contain a lot of oil & so burn very easily
How do different types of fuels affect wildfires? [2]
- Fine, dry material catch fire & burn most easily
- Large amounts of fuel forming a continuous cover will help the fire spread
How does the climate affect wildfire intensity? [3]
El Nino: Increases intensity of wildfires in North America
- Warm, dry weather causes vegetation to dry up, so it’s more flammable
- Strong winds help the fire burn & spread easily
What are different behaviours of fires? [3]
- Creeping fire: moves across ground surfaces fairly slowly
- Running fire: spreads rapidly & more intense
- Burning debris: helps fire spread & become more intense
Natural causes of wildfires [3]
- Lightning
- Spontaneous heating
- Volcanic eruptions
Human causes of wildfires [3]
- Dropping cigarettes, campfires, matches
- Arson
- Fireworks
What % of wildfires are human caused
85%
What is the ladder effect?
- A wildfire climbing into the canopy
Name 2 social impacts of wildfires
- People may be killed or injured if they don’t evacuate in term
- Wildfires can cause health problems e.g. inhaling smoke can cause long-term breathing difficulties
Name 2 Political impacts of wildfires
- Governments can face criticism when wildfires have severe impacts
- Gov’s may have to change forest management practices to reduce wildfire risk e.g. clearing vegetation to limit fuel
Name 2 Economic impacts of wildfires
- Wildfires can destroy businesses -> loss of jobs & income
- Fighting wildifres is costly
Name 2 Environmental impacts of wildfires
- Soils are damaged as the fire removes organic matter
- Habitats are destroyed
Short-term responses to wildfires [4]
- Diverting away from settlements
- Evacuating people from at-risk areas
- Trying to put the fire out
- Spraying water on roofs of houses to prevent them setting alight
Prevention against wildfires [2]
- Public education about the risks of using campfires and BBQs in vulnerable areas
- Authorities may provide fire beaters to put small fires out before they spread
Preparedness for wildfires [2]
- Households having an emergency plan & supplies of food, water & medicine
- Authorities making emergency shelters available
Adaptation for wildfires [2]
- Using non-flammable building materials
- Creating fire breaks (gaps in trees) around settlements to stop fire spreading
[ALBERTA 2016] Spatial + Temporal setting [6]
- Spread 540,000 hectares before control on 5th July
- 10% of city = destroyed
- Local state of emergency: May 1st 9:57pm
- First spotted 15km from Fort McMurray
- May 4th- large enough to make a firestorm
- August 2nd 2017- extinguished
[ALBERTA 2016] Perceptions of the wildfire [2]
- May 2nd + 3rd, people went to school
- 21.6% before the fire thought it had x threat to family
[ALBERTA 2016] Causes of wildfire [4]
- No evidence of natural cause - lightning strikes
- “Perfect storm” of conditions, e.g. 32.8•C, 72km/hr winds, El Niño 2016
- $15mill fire protection budget cut month before.
- Reduction of patchwork forests over time.
[ALBERTA 2016] Impacts of the wildfire [4]
- $3.6 billion in damages, 88,000 evacu.
- 2,400 homes destroyed
- Production of 1 mill oil barrels/day halted (1/4 of Canada’s oil production)
- Mass job loss + unemployment
[ALBERTA 2016] Response to the wildfire? [4]
- ‘Fort McMurry Strong’ signs
- Wood Buffalo Report, recommendations given on how to respond, e.g pet rescue
- Some communities 1yr later being rebuilt
- Prime Minister turned down aid from Australia, Israel, Mexico + Russia
