Hazards Flashcards
What are the types of hazards
Geophysical-caused by land processes
Atmospheric-caused by climatic processes
Hydrological-caused by the movement of water
What is a disaster
when a hazard actually seriously affects humans
What is risk
likelihood that humans will be affected
What is vulnerability
how susceptible a population is
What are humans responses to hazards
Fatalism: cannot be avoided so must be accepted
Prediction: work out when and where the hazard will occur
Adaptation: adjusting how you will live
Mitigation: attempt to reduce the impact of the hazard
Risk sharing: share the cost of reducing a hazard e.g insurance
What is a persons response to a hazard based on
hazard incidence(how often)
intensity/magnitude
distribution
level of development
What is the theory of plate tectonics and the evidence to support it
Continental drift theory
Lithosphere divided into plates. Used to be one mass(Pangaea)
Evidence for continental drift theory: fossil remains, seams of rock types, jigsaw shape of continents, palaeomagnetism
How does palaeomagnetism support continental drift theory
Palaeomagnetism supports plate tectonics as it can be used to show that the oceanic crust has experienced seafloor spreading, where new crustal material pushes old crustal material away from the ridge. Paleomagnetic data can also be used to show how the continents have moved over time through apparent polar wander paths.
What are the theories that show HOW plates move
convection currents (main)
slab pull (most dominant)
ridge push
What are the layers of the earth
inner core
outer core
mantle
crust
Properties of the inner core
solid
iron and nickel
6,000C
Properties of the outer core
semi molten iron and nickle
Properties of the mantle
mostly rocks containing silicon
has the asthenosphere under the crust which is semi-molten
1000-3500C
properties of crust
forms the lithosphere
What are the two types of crust
continental (thicker less dense)
30-70km
oceanic (thinner, denser)
6-10km
What can form at a constructive margin
Ocean ridge
rift valley-
rising magma causes crust to bulge and fracture, causing faults. Lands between faults drops down to form rift valley
volcanoes-
basaltic lava which is very hot, low viscosity. Frequent eruptions. Form shield volcanoes
earthquakes-
low magnitude
What can form at a oceanic-continental destructive margin
Fold mountains-
Andes mountains
Volcanoes-
cone shaped. Andesitic and rhyolitic lava which is cooler and more viscous so flows less easily. Violent eruptions
deep sea trench
earthquakes
What can form at a destructive oceanic-oceanic plate margin
Islands arcs-
Mariana islands. Sit in a curved line above a plate margin
deep sea trench-
Mariana trench
volcano
earthquakes
What can form at a destructive continental continental plate margin
earthquakes
fold mountains-
Himalayas
NO VOLCANOES -NO SUBDUCTION
What forms at a conservative plate margin
earthquake-
plate get locked together and pressure builds up
fault lines-
cracks form
San Andreas fault
What forms at magma plumes
volcanoes
chain of volcanic islands-
hawaii
What are the stages of the park hazard model
Pre-disaster
Disaster
relief
rehabilitation
reconstruction
What are the positives of the park hazard response models
Helps predict resources needed at each stage, improvement mitigates future impacts, reduces vulnerability, curve tracts progress overtime
What are the negatives of the park hazard model
assumes normality doesn’t factor in events in quick succession, LIC/NEE may not be able to afford improvements
What are the stages in the hazard management cycle
mitigation
preparedness
response
recovery
What is the positive of the hazard management cycle
cycle=events keep happening, ongoing mitigation to reduce impact
What is the negative of the hazard management cycle
less suited to unexpected hazards, LIC/NEEs may not be able to afford some stages, doesn’t track progress over time
What are pyroclastic flows
super-heated mixture of gas nd tephra that flows at speeds of up to 700km/h
What is tephra
ash fallout
What are lahars
volcanic material mixes with water
What causes the variation in volcanic hazards
Magnitude
frequency
randomness vs regularity
predictability
What are the secondary seismic hazards
tsunami
landslides/avalanche
soil liquefaction
What scales measure earthquakes
richter scale-
logarithmic
moment magnitude scale-
total amount of energy released
mercalli scale-
uses observations
What are the conditions and location of tropical storms
occur in latitudes between 5 and 30 north and south of the equator
deflected away from the equator by Coriolis effect
move westwards due to easterly winds from the tropics
Anticlockwise in north hemisphere and clockwise in south
27C water
low pressure
convergence of air itcz
What scale measures tropical storms
Saffir Simpson scale
What are the causes of the extreme heat in the earth’s core
Radioactive decay of elements such as uranium and potassium
Residual heat from the collisions of asteroids and other small bodies resulted in the formation of earth
What is the main driver of tectonic activity
heat from the earths core
Who proposed continental drift theory
Alfred Wegener
What is convection current theory
Explains tectonic plate movement as the result of heat from radioactive decay in the core moving upwards in the mantle, creating currents that carry the lithospheric plates above
Describe slab pull
Process where gravity pulls a subducting plate down into the mantle at a subduction zone
What is palaeomagnetism
evidence that the sea floor has gradually moved apart at a mid-ocean ridge. It is shown by the alignment of minerals in cooled lava with the Earth’s magnetic field
What is seafloor spreading
process by which new oceanic crust is formed at mid-ocean ridges and moves away from the ridge over time
What is gravitational sliding/ridge push
process where gravity pulls the lithosphere down the slope created as new oceanic crust cools and becomes denser. This pushes the crust forward
Define constructive plate boundaries
plates move apart. Leads to new crust being formed
What is a rift valley
diverging plates are beneath the land, causing the crust to stretch and fracture, with areas of the crust dropping down between faults to create a valley
What is the benioff zone
where earthquakes occur along the subduction slab at a destructive plate boundary
Define a conservative plate boundary
where plates slide past each other in opposite or the same direction at different speeds
What types of volcanoes typically form at destructive plate boundaries
Steep-sided, composite volcanoes with andesitic and rhyolitic lava flows
What is an island arc
Curved chain of volcanic islands forming where submarine volcanic eruptions lead to crust building up and rising above sea level at oceanic-oceanic destructive boundaries
How do fold mountains form at a continental- continental collision boundaries
two plates of silimar density move towards eachother and neither is dense enough to subduct, pushing the land upwards
What are hot spots
areas around the core of the earth where radioactive decay is concentrated, creating extreme heat
What is a magma plume
upwellings of superheated rock that rise from deep within the earths mantle towards the surface
What is an island chain
series of volcanic islands formed when a tectonic plate moves over a stationary magma plume
How are island chains formed
tectonic plate moves over a stationary magma plume, creating a series of volcanoes that become active when above the plume and extinct as they move away
How do magma plumes differ from other sources of volcanic activity
Magma plumes causes volcanism within tectonic plates not just at plate boundaries
What happens to volcanoes in an island chain as they move away from the magma plume
they become extinct
Where do most active volcanoes occur
75% occur on the ring of fire
What type of lava is typically found at constructive margins
Basaltic lava
low gas content, low viscosity and higher temperature, typically found at constructive margins
What is VEI
logarithmic scale from 0-8
measures the magnitude of a volcanic eruption
based on factors such as the height of the material ejected
What type of eruptions typically occur at destructive margins
tend to be explosive as the magma is forcing its way to the surface , often with andesitic or rhyolitic lava
What are the characteristics of lava at destructive margins
high gas content
high viscosity
lower temperature
How do eruptions at constructive margins typically differ from those at destructive margins
Eruptions at constructive margins tend to be small and effusive, while eruptions at destructive margins tend to be explosive
What is tephra
solid material with a range of size that volcanoes eject, from ash to volcanic bombs
What is jokulhlaup
A flood caused by a sudden release of water and rocks when glacial ice is melted by a volcanic eruption
Why are pyroclastic flows considered one of the deadliest volcanic hazards
they travel long distances and destroy everything in their path
How does acid rain form as a result of volcanic activity
forms when sulphur dioxide emitted during the eruption reacts with water vapour in the atmosphere to form sulphuric acid
What is a lahar
mudflow that occurs when tephra mixes with water, from rainfall or melted snow
What type of volcanoes are typically found at constructive plate margins
Shield volcanoes
Define stratovolcano
type of volcanoes found at destructive plate margins, characterised by low frequency, high magnitude eruptions
What do scientists look for to predict a volcanic eruption
magma rising
ground deformation
increased emissions of gases
increased seismic activity
What tools do volcanologists use to monitor changes in volcanic activity
GPS
tilt meters
satellites
seismometers
gas detection
What is hazard mapping
long term response to volcanic hazards that involves identifying areas at greatest risk and limiting the activities that can take place there
What are p waves
primary seismic waves that are the fastest, reach the surface first, travel through liquids and solids, cause backwards and forward shaking
What is liquefaction
shaking causes loose or saturated soils to lose their strength and act like a liquid rather than a solid
What are S waves
secondary seismic waves that are slower than p waves, only travel through soils and cause sideways motion
Which type of seismic wave is the most damaging
L waves are surface seismic waves that are the slowest, causes side-to-side motion and are the most damaging
What is the moment magnitude scale
used to measure the magnitude of earthquakes ranging 1 to 10
What does the Modified Mercalli intensity scale measure
measures the intensity of an earthquake, which is its impact on people, as well as on the built and natural environments
What is seismic gap theory
It suggests that if there has been little or no earthquake activity at a plate margin for a long time, it is more likely to experience a large earthquake in the future
Concentrations of which gas in the atmosphere may increase before an earthquake
radon gas
What is japans disaster prevention day
annual event held on september 1st to prepare communities and improve evacuation and response through regular drills
What is the minimum wind speed for a tropical storm
over 119km/h
What is the minimum sea-surface temperature for a tropical storm formation
over 27C
What is a storm surge
occurs when large volumes of water are forced inland by the low pressure and string winds associated with tropical storms
What is the eye wall of a tropical storm
consists of large cumulonimbus clouds that form around the eye of the storm.
It has the highest wind speeds and heaviest rainfall
What is the saffir-simpson scale
measures tropical storm intensity based on wind speeds
What types of data are gathered for tropical storm prediction
atmospheric pressure
wind speed and direction
humidity
sea surface temperature
ocean currents
Ways in which building design can help withstand tropical storms
building on stilts to avoid flood waters
building with reinforced concrete
fixed roofs rather than tiles
What are the three types of wildfire
ground fires
surface fires
crown fires
What is a crown fire
They burn through the canopy layer (top layer of vegetation)
Usually the most dangerous and destructive type of wildfire because they move quickly and often produce intense heat and flames
What is a common natural cause of wildfire ignition
lightning storms
What are long-term environmental impacts of wildfires
increased soil erosion and leaching
damage to the soil and loss of soil fertility
increased risk of flooding
release of co2 contributing climate change
Ways in which people can reduce the risk to their homes from wildfires
prune trees and keep them a safe distance from the house
stack firewood at least 10m from the house
mow grasses and weeds to keep them short
reduce vegetation close to the house
clean gutters and roofs to reduce debris
What type of tree growing in australia is highly flammable
euclyptus
What is backburning
strategy where firefighters light small fires ahead of a larger wildfire to reduce the amount of fuel available to help slow or stop the spread of the fire
