Hazards Flashcards
Difference between oceanic and continental crust
Oceanic crust: more dense, hard balsaltic, less thick
Continental crust: Less dense, soft granite, thicker
Difference between a natural event and a natural hazard
Natural event = feature that occurs due to earth’s processes
Natural hazard = when a natural event can cause loss of life or damage to property
Geophysical hazards
Geophysical hazard = caused by earth’s processes - internal (tectonic), external (mass movement)
Hydrological hazards
Hydrological hazards = caused by occurence/movement/distribution of water
Atmospheric hazards
Atmospheric hazards = within the atmosphere eg exteme weather events
When do hazards become a disaster?
Hazards become a disaster in a vulnerable population -> Dregg’s model
Plate boundaries
Plate boundaries:
-Collision
-Transform/Conservation
-Divergent/Constructive
-Convergent
Collision plate boundary
Collision plate boundary:
-Equal density, folds upwards and creates mountains
-Earthquakes only, himalayas
Transform/Conservative boundary
Transform/Conservative argument:
-Plates slide past eachother, friction released
-Earthquakes only
-San-andreas fault in California
Divergent/Constructive boundary
Divergent/Constructive boundary:
-Plates move away from eacother
-Forms Ocean Ridge system
-Underwater mountains + volcanoes
-Shield volcanoes and easthquakes
-Rift valleys
-Mid-alantic Ridge
Convergent boundary
Convergent boundary:
-Denser ocean plate subducts -> downward placement forms a deep-sea trench -> sediment unfolded
-Composite volcanoes and earthquakes
Why do plate boundaries move?
Plate boundaries move due to ridge push, slate pull and convection currents
Evidence of continental drift
Evidence of continental drift:
-Geological fit (similar rock types in different areas)
-Tectonic fit (plate movement causes land movement)
-Jigsaw fit (countries fit together)
-Paleomagnetism
-Fossil evidence
Factors that affect viewpoints of how dangerous hazards are
Factors that affect viewpoints of how dangerous hazards are:
-Wealth
-Experience
-Education
-Religion and beliefs
-Mobility
Passive response to a hazard
The passive response to a hazard = fatalism = viewpoint that hazards are uncontrollable natural events and losses should be accepted
Active responses to a hazard
Active responses to a hazard:
-Prediction
-Adaptation
-Mitigation
-Management
-Risk sharing
Aspects of hazards that could affect human responses
Aspects of hazards that could affect human responses:
-Frequency
-Distribution (where the hazard occurs)
-Intensity
-Magnitude
-Level of development
The Park Model
The Park Model is a graphical representation of human responses to hazards
-Step 1 = Relief (hrs/days) = immediate local response
-Step 2 = Rehabilitation (days/weeks) = Services, shelters, food and water
-Step 3 = Reconstruction (weeks/yrs) = restoring the area back to normal
Outline the earth’s structure
Earth’s structure:
-Inner core = solid ball of iron/nickel, hot due to pressure and radioactive decay
-Outer core = semi-molten, iron/nickel
-Mantle = solid rock, silicon, semi-molten magma layer called aesthenosphere with lithosphere ontop
-Crust = thin top of lithosphere
Outline the movement of convection currents
Convection currents:
-Heat from core convects through mantle
-hot magma rises as it becomes less dense
-magma cools at top and sinks
-this movement causes tectonic plates to move
Hazards caused by volcanoes
Volcanic hazards:
-Lava flows
-Lahars (mudflows)
-Glacial floods
-Tephra (rock ejected from the volcano)
-Toxic gases
-Acidic rain
-Pyroclastic flows
Volcano distribution
Volcano distribution - along constructive or deconstructive plate boundaries or hotpots - ring of fire
Volcano magnitude
Volcano magnitude is measured using the Volcanic Explosivity Index (VEI)
Primary impacts of volcanic hazards
Primary impacts of volcanic hazards:
-Damaged ecosystems
-Businesses destroyed
-People killed
-Homes destroyed
-Government buildings destroyed
Secondary impacts of volcanic hazards
Secondary impacts of volcanic hazards:
-Acidic rain
-Loss of jobs
-Forest fires
-Government conflicts
Responding to a volcanic hazard
Responding to a volcanic hazard:
-Prevention - not allowing people near
-Preparedness - increased monitoring, education
-Mitigation - strengthening buildings, evacuation zones
-Adaptation - moving away from risky areas, tourism for better opportunities to increase mitigation
What are the immediate responses to volcanic eruptions?
Immediate response:
-Aid
-Warnings and monitoring
-Evacuation
-Temporary infrastructure (shtlers)
What are the long-term responses to volcanic eruptions?
Long-term responses to volcanic eruptions:
-Education
-Relocation using resettlement programmes
-Improve locale economy
-Rebuild infrastructure
Mitigation and adaptation strategies to tectonic hazards?
Mitigation and adaptation strategies to tectonic hazards:
-Land-use and buildings
-Physical defences ie diversion
-Community preparedness
-Modifying loss (aid, compensation)
What is the difference between the focus and the epicentre of earthquakes?
Focus = where the pressure is released/originates from
Epicentre = where the earthquake is felt on the earth’s surface
Types of earthquakes
The types of earthquakes include:
-Shallow-focus earthquakes = focus is close to the earth’s surface
-Deep-focus
-Underwater -> cuases water displacement -> leading to tsunamis
Different waves created by earthquakes
Different waves created by earthquakes:
-L-waves (love waves) (significant damage, across surface)
-P-waves (primary waves, fast)
-S-waves (secondary, makes ground shake)
Primary and Secondary hazards of earthquakes?
Primary hazards: Ground shaking, crustal fracturing
Secondary hazards: Landslides, Liquefaction (waterlogging sediment), tsunamis
Tsunami characteristics
Tsunami characteristics:
-Long wavelength
-Short amplitude at sea, increases at shore
-Quick velocity
-Drawback of water at coasts
Predicting hazards
Predicting Hazards:
-Seismometers tell where earthquake has occured + can indicate magma movement for volcanoes
-Tiltmeters can redocrd volcanoes ‘bulging’ as magma rises
-Gas spectrometers analyse gas emissions at volcanoes
Immediate responses to earthquakes
Immediate responses to earthquakes:
-Temporary housing
-Evacuations or warnings
-Aid
-Temporary infrastructure
-Rescue operations
Long-term responses to earthquakes
Long-term responses to earthquakes:
-Rebuilding infrastructure
-Improve local economy
-Improve preparation
How to mitigate earthquake damages
Mitigating earthquake damage:
-Physical defences (eg tsunami defences such as seawalls)
-Education
-Land-use zoning (preventing building on vulnerable coasts)
-Infrastructure defence - deep foundations, shock absorbers, deep glazing
Describe the earth’s core
Core of the earth:
-Made up of dense rock containing iron and nickel
-Divided into inner and outer
-Temp above 5000 degree celcius
-Heat produced due to primordial heal from earth’s formation and radiogenic heat from radioactive isotype decay
Describe the earth’s mantle
The earth’s mantle:
-Thickest layer
-Made up of molten and semi-molten rock rich in iron and magnesium
-Outer layer - aesthenosphere
Describe the crust of the earth
Earth’s crust:
-Two layers: thin layer of dense balsalt under oceans and less dense thick granite rock making up the continents
What is the plate tectonic theory?
The plate tectonic theory = the theory of continental drift
Reasons for plate movement
Plate movement is caused by:
-Convection currents within the mantle
-Ridge push/Gravitational sliding (less dense hot magam wells up and produced ocean ridge, cools and becomes dense - graviety acting on this causes sliding from the ridge)
-Slab pull (the force that the sinking edge exerts on the rest of the plate as it subducts)
Nature and distribution of volcanoes
Nature and distribution of volcanoes:
-Along constructive plate boundaries
-On or near subduction zones
-Over hotspots
Method of measuring magnitude of volcanic activity?
Method of measuring magnitude of volcanic activity = The volcanic explosivity index (VEI)
-Frequency is measured by looking at previous activity
Primary effects of volcanic activity
Primary effects of volcanic activity:
-Tephra (solid material of varying size eg ash into the atmosphere)
-Pyroclastic flows
-Lava flows
-Volcanic gases
Secondary effects of volcanic activity
Secondary effects of volcano activity:
-Lahars (volcanic mudflows)
-Flooding due to melting glaciers from the heat
-Volcanic landslides
-Tsunamis
-Acid Rain
-Climatic change
Responses to volcanic hazards
Responses to volcanic hazards:
-Preparedness (monitoring gases, lava levels, bulging of land, small earthquakes
-Mitigation (risk assessments, diverting lava flow, seawater on lava flow, barriers)
-Adaption (relocation)
Phillipines Volcanic Event details
Phillipines volcanic event:
-Mount Mayon, 2000+ meters above sea level
-Composite volcano
-Historic eruptions
-Surrounded by city and towns
-Popular tourist spot
Phillipino Mount Mayon (2018) risk and vulnerability
Phillipino Mount Mayon (2018) risk and vulnerability:
-Large ash emissions acros land
-Heavy lava flows against local agriculture
-Historical dataP
Phillipino Mount Mayon (2018) impacts
Phillipino Mount Mayon (2018) impacts:
-No deaths
-Well-organised emergency procedures
-Responses: hygenic packages for families, military support, first-aid stations, international help from United states
Focus of an earthquake
Earthquake focus: Point at which the pressure is released
Earthquake epicentre
Earthquake epicentre: Point where it is first felt on the earth’s surface
Effect of human acitvity on earthquakes
Effect of human activity on earthquakes:
-Building large reservois which puts pressure on underlying rock
-Subsidence of deep min workings
-Fracking of rock to release gas
Measuring earthquake magnitude
Measuring earthquake magnitude:
-Moment magnitude scale (in terms of energy released)
Primary effects of seismic activity
Primary effects of seismic activity:
-Ground shaking caused by shock waves
-Ground rupture
-Infrastructure damage
-Ecosystem damage
Secondary effects of seismic activity
Secondary effects of seismic activity:
-Soil liquefaction (soils with high water content lose strength and becomes fluid)
-Land slides/avalanches
-Tsunamis - generated by shallow focus underwater earthquakes
Creation of tsunami
Creation of tsunami:
-Earthquake rocks the ocean floor
-Displaces volume of water, pushing it up
-Sets off an oscillation, which develops underwater at great speed
-Sea water is sucked back from shore
-Waves get bigger as water gets shallower
What does effects of tsunami depend on?
The effects of tsunamis depend on:
-Wave height and distance
-Length of event at souce
-Extent to which warnings could be given
-Coastal physical geography, land use and population density
Tsunami example
Tsunami example - march 2011 Tohoku - caused by 9.0 earthquake, over 40km i height and 16k deaths
Responses to seismic hazards
Responses to seismic hazards:
-Prepardness (secured furniture, communication plan, emergency supply kit)
-Mitigation (early warning systems, hazard-resistance structure ie foundation and rubber shock absorbers_
-Adaptation (identify risk areas, relocation)
Tropical cyclone features
Tropical cyclone features:
-Cyclone/Hurricane/Typhoon
-Low pressure weather systems that develop in the tropics
-26celcius+ waters
-Coriolis force
Measuring cyclone magnitude
Measuring cyclone magnitude = saffir simpson scale (5 point scale determined by wind speed)
-doesnt take other factors into account ie storm surges, flooding and rainfall
Impacts of climate change on tropical cyclones
Impacts of climate change on tropical cyclones:
-Air temp above warmer than water resulting in enhanced uplift
-Oceanic evaporation -> increased atmospheric water vapour
What does vulnerability to tropical cyclone depend on?
Vulnerability to tropical cyclones depend on:
-Intensity of storm (1-5(
-Movement speed
-Coastal area geography
-Warnings and community response
Major impacts of tropical cyclones
Major impacts of tropical cyclones:
-Winds
-Heavy reinfall
-Storm surges
Response to storm hazards
Response to storm hazards:
-Preparedness (weather satellite data, warning system, storm shelter construction)
-Mitigation (resillient infrastructure)
-Adaptation (land-use planning, sea walls and flood barriers
Typhoon Haiyan details
Typhoon Haiyan
-Phillipines deadliest typhoon
-High density population and overcrowded residential areas - vulnerable
-Heavy rainfall
-High storm surges
-6000 deaths
-Damage to inrfrastructure, homlessness, almost 3 billion in damages
What is slab pull?
Slab pull occurs when denser oceanic plate is subducted under the less dense continental plate
What is ridge push?
Ridge push is when magma rises from the mantle -> cools and slides downslope due to gravitational force -> causing plates to move
What is sea floor spreading?
Sea floor spreading occurs when two oceanic plates move away from eachother -> causing magma to rise -> forms new crust ridges when cools
