Hazards Flashcards
what are geophysical hazards?
volcanic and seismic hazards related to the lithosphere
what are atmospheric hazards?
includes tropical storms, droughts and tornadoes . Hazards related to the atmosphere
what are hydrological hazards?
involve flooding and are related to the hydrosphere
what is risk?
the potential for loss
what is vulnerability?
the exposure to hazards and ability to cope with them
what is resilience?
the degree to which a population or environment can absorb a hazardous event
what are features that increase resilience?
- emergency evacuation, rescue and relief systems in place
- helping each other/ community
- having a hazard resistant design or land use planning
why is it difficult to compare impacts between countries?
- the physical nature of the event is different
- the socio-economic characteristics of places are different
- economic costs in developed economies are large, but they are less costly in developing countries
- deaths in developed countries are lower
what are influences of vulnerability?
inequality of access to education, housing, healthcare, income
what is the fatalist approach to a hazard?
where people accept the risk and choose to do little about it. More likely in developing countries/LICs
what is a destructive plate margin?
when oceanic plate slides beneath continental plate and crust is destroyed as one goes beneath the other towards the subduction zone
what is a conservative plate margin?
plates sliding past each other horizontally
what is a constructive plate margin?
plates move apart from each other
characteristics of oceanic plate?
- high-density
- made of basaltic rock
- 7-10km thick
- subduct beneath other plates
characteristics of continental crust?
- 25-75km thick
- less dense
- granite- do not sink
what is an island arc?
- form at destructive subduction boundaries, when the descending plate melts and material rises towards the surface as magma
- when plutons of magma reach the surface they form volcanoes which may erupt offshore, causing al ine of volcanic islands eg. Marianas trench
what are volcanoes?
- found at constructive and destructive subduction boundaries, where the melted plate rises to the surface
what are deep sea trenches?
- found at destructive subduction boundaries, where oceanic subducts under continental eg. Marianas trench
what are fold mountains?
- destructive subduction and destructive collision boundaries
- as plates move together, sediment in the sea is pushed up into folds between them
what are rift valleys?
- formed at constructive plate boundaries where 2 continental plates pull apart
- as the crust thins it is heated forming cracks
- when an area of crust drops down between two parallel faults this is a rift valley
what are ocean ridges?
- formed at constructive boundaries where 2 oceanic plates pull apart
- as pressure is reduced the semi-molten magma of the mantle melts and rises up into the gap between the plates forming a ridge eg. mid-Atlantic
what is a hazard?
a natural event that has the potential to threaten both life and property
what is the distribution of hazards like?
uneven- some areas of the world are at low risk some are at high risk
- distribution of earthquakes is uneven- pacific ring of fire mainly
what are hotspots?
- a hot mass or rising heat under a weakness in a plate
- magma rises to the surface through the weaknesses
what is the lithosphere?
the crust and upper mantle (80-90km) which form the tectonic plates
what is the mantle?
the mantle is a semi molten body of rock between the earth’s crust and its core
what is the core?
the central part of the earth
what is the asthenosphere?
lower part of the mantle
what is gravitational sliding?
elevated altitudes of oceanic crust at ridges at divergent plate boundaries- creating a slope down which oceanic plates slide
what is sea floor spreading?
- in the 1960s, there was a discovery of magnetic stripes in the oceanic crust of the seabed
- paleomagnetic signals from past reversals of the Earth’s magnetic field prove that new crust is created by the process of seafloor spreading at mid-ocean ridges
what is slab pull?
at convergent boundaries, high density ocean floor is being dragged down by a downward gravitational force beneath the adjoining continental crust
what did Wegner say about continental drift?
1912- said that our now separate continents had once been joined together as super continents eg. Pangea
what happens at a collision margin?
characterised by the meeting of two continental landmasses resulting in the formation of a fold mountain belt
what happens at a transform margin?
- no volcanic activity
what is pyroclastic and ash fallout?
- any material that has been ejected from a volcano and has travelled through the air and fallen onto earth
what are pyroclastic flows/nuees ardentes?
- currents of hot ash, lava and gas that move downhill during an eruption
what are lahars?
- if volcanic ash or lava mixes with water lahars (mudflows) form
- fast moving flows of volcanic material and water
what is tephra?
- rock fragments that are ejected from the eruption
how can you predict volcanic eruptions?
- gas emissions
- seismic waves
- thermal images (magma)
- volcanic swelling
what is a jokulhlaup?
the name of the flooding that happens when glaciers or ice caps melt
what are immediate responses to an eruption?
- aid
- evacuation
- warnings and monitoring
- temporary infrastructure
what are the long term responses to volcanic eruptions?
- education
- improve local economy
- rebuild infrastructure
- relocation
what are effective mitigation and adaptation strategies?
- physical defences
- land-use and buildings- resistant infrastructure- land use zoning
- community preparedness and education
- modifying loss- aid/compensation
what is the focus?
where the pressure is released underground and where the energy radiates from
what is the epicentre?
the point above ground directly above the focus
what are the 3 types of EQ?
- shallow focus-0-70km beneath surface
- deep focus- 70-700km- less damaging
- underwater EQs- move the seabed causing water to be displaced
what are the primary hazards of EQs?
- ground shaking
- crustal fracturing- earth splitting apart
what are the secondary hazards of EQs?
- landslides
- liquefaction
- tsunamis
how is a tsunami created?
the seabed is displaced vertically- this motion displaces a large volume of water in the ocean column which then moves outwards from the point of displacement
what is a collision plate margin?
- two continental plates move together= fold mountains
how do you mitigate against the impact of EQ’s?
- physical defences
- education
- land-use and buildings
- EQ proof buildings
- alert system
what causes a tropical storm?
- warm air rising from oceans with over 27° will create pockets of low pressure. These will draw in warm air from the surrounding area
- if this occurs between 5-20° N or S of equator the Coriolis force means these systems will rotate
- as more warm air is drawn in, they grow into tropical depressions and eventually tropical storms
what is the structure of a tropical storm?
- 200-700km wide with rotating spiral of clouds
- eye usually 10-15km in diameter- calm
- strong conditions in eye wall
- energy dissipates over ground
what hazards are associated with tropical storms?
- heavy rainfall
- storm surges
- strong winds
how are storms measured?
on the saffir-simpson scale- largest storms reaching category 5
how frequent are tropical storms?
- around 100 tropical storms form in the Atlantic each year with 5.9 becoming hurricanes
- frequency increase linked to global warming
