Natural Hazards Flashcards
what is an avalanche
an avalanche is a slide of large snow or rock mass down a mountainside, caused when a build up of snow is released down slope
what is a landslide
a landslide is related with an avalanche but instead of snow it occurs with actual elements of the ground including rocks, houses, trees. they can be caused by earthquakes, volcanic eruptions or instability of surrounding land
what is a mudflow
mudslides or mudflows are a special case of landslides in which heavy rainfall causes loose soil on steep terrain to collapse and slide downwards
what is a flood
floods are the result of prolonged rainfall from a storm including thunderstorms, rapid melting of large amounts of snow etc and cause widespread damage from flooding etc
what is a wildfire
an uncontrolled fire burning in wild land areas. commonly caused by lightning and drought however can be started by human negligence or arson
what is a cyclonic storm
hurricane, cyclone and typhoon are different names for the same phenomenon of a cyclonic storm forms over oceans. it ios caused by evaporated water that comes off to the ocean and becomes a storm
what is a tornado
a tornado is a natural disaster resulting from a thunderstorm. tornadoes are violent rotating columns of air which can blow at speeds between 50 to 300 mph
what is a tsunami
a wave of water caused by the displacement of a body of water. tsunami can be caused by undersea earthquakes
what is a volcanic eruption
a volcanic eruption is the point in which a volcano is active and releases its power. they mainly occur along tectonic plates
different responses to hazards
what is fatalism
people with fatalism view are often used to experiencing these hazards and may have lived through events many times. they see that the cons of living with a hazard are smaller than the benefits which can be offered
what is adaption/adjustment
the adaption approach is when a town or city starts to change their way of living to fit natural disasters into their everyday lives
what is prediction
knowing when a hazard will occur is hugely advantageous and can lead to significantly reducing death tolls and overall impacts. prediction can occur through different ways such as seismic monitoring, measuring has emissions and geological ground changes
what is mitigation
any action taken to reduce or eliminate threat to property or human life as a result of a natural hazard. this can include the idea of adaptation but can also include anything done on an individual level to reduce the impact of a hazard upon an individual. any mitigation carried out ned to go through a cost benefit analysis to ensure that its economically viable
what is risk sharing
when a natural hazard event occurs somebody always looses out. risk sharing works on the principal that spreading the risk reduces anyone, group or individuals risk therefore making it more acceptable while also may involve sharing the financial burden
what is management
the degree of management carried out heavily depends on the wealth of a nation
what is the park model
the park model if hazard response considers how the standard of living and economic status of an affected area changes following an event
what is the standard of living phase
how much you have and can buy economically
what is the relief phase
the immediate response, focus is on saving lives and property, charity teams such as the red cross, from outside the immediate area help with search and rescue and care operations, urgent medical supplies, rescue equipment and food may be brought in
what is the rehabilitation phase
more complex than relief, this may last for several months where efforts are made to restore physical and community structures or at least temporarily
reconstruction, mitigation and preparedness phase
permanent changes are introduced to restore the quality of life and economic stability to the pre disaster level or better this can also include mitigation and preparedness reducing vulnerability
hazard management cycle phases
-hazard event
-response
-recovery
-preventation/mitigation
-preparation
hazard event phase
-hazard severity probability
-vulnerability: root causes, social forces, unsafe conditions
response phase
-rescue and evacuation
-relief and external support
preventation/mitigation
-ongoing processes to lesson the severity of hazard on people/property
-rebuild buildings and houses
-introduce prediction methods
preparation phase
-actions prior to event to activate necessary resources
-shelter to go to stay safe
-leave the area that could get highly impacted
what are the different structures of the earth
-inner core
-puter core
-mantle
-crust
-asthenosphere
-lithosphere
what is the lithosphere
the slid top layer os the crust in which plates are formed, consisting of crust and upper mantle
what is the athenosphere
soft plastic like rock in the upper mantle just below the lithosphere
earths energy
-earths energy is left over from when it formed by arising from a cloud of gas and dust in space
-earth cools very slowly, to keep a steady temperature because it makes heat in its interior
-earths producing as much heat as its loosing through the process of radioactive decay which involves the disintegration of natural radioactive elements inside earth and when it decays it produces heat
-many rocks in earths crust and interior undergo this process of radioactive decay
-the rest of travel of waves from earthquakes are called ‘seismic waves’ which tells scientists about what material make up the planet
convection currents in the mantle process
- heat source - radioactive decay in the heat source
- rising limb of convection current. heated rock in mantle rises as it is less dense
- direction of plate movement due to movement of convection current below
- semi molten rock spreads out carrying the above plate with it
- cools and sinks back down to be reheated
plate boundary types
-constructive
-destructive
-collision
-conservative
constructive plate boundary
- at a constructive plate margin two plates are moving apart leaving a gap in the middle for magma to rise up through
-volcanoes form but dont erupt with force as the magma can escape easily
-earthquakes can also occur such as the mid atlantic ridge
-rift valleys can also form as land falls down into the space left as plates move apart
-mid ocean ridges and rift valleys can form at this plate boundary
destructive plate boundary
-at a destructive plate boundary dense oceanic plate descends below less dense continental plate
-as the plate descends it is melted due to friction with the continental plate, farming hot liquid magma
-this magma can then rise through cracks in the continental plate and form volcanoes if it reaches the surface
-earthquakes, volcanoes, fold mountains, ocean trenches can all form at this boundary
collision plate boundary
-collision plate boundaries occur when two plates of similar densities move together which causes material between them to buckle and rise up forming fold mountains
-the Himalayas are an example of this
conservative plate boundary
-conservative plate boundaries exist where two plstes do not directly collide but slide past each other along a fault
-no volcanoes are found along these boundaries but earthquakes occur
-such as the san andreas fault in california
-powerful earthquakes occur at this plate boundary
what are the three types of destructive boundaries
- oceanic- continental
-oceanic - oceanic - continental - continental
oceanic - continental plate boundary
-the oceanic crust which is thinner snd more dense than the continental crust sinks below the continental crust into the upper mantle
-this process is known as subduction
-destructive margins are some of the most seismically active zones in the world with shallow to deep focus earthquakes
-deep ocean trenches are found along the sea ward edge of the destructive margins
oceanic - continental ocean trenches
- as the dense oceanic nazca plate is sub ducted beneath the continental south american plate a deep ocean trench
-the trench extends 8km down in places is 64km wide
oceanic - continental fold mountains
-pressure put onto the continental crust can cause it to buckle upwards and from fold mountains
-in addition material on the ascending oceanic plate is scraped off and folded to form the mountain
oceanic - continental volcanoes
-benioff zone the further the rock descends the hooter the surroundings become. this together with the heat generated from friction begins to melt the oceanic plate into the magma
-as it is less dense than the surrounding asthensphere the molten material begins to rise in the great plumes up through fissures/faults in the buckled continental plate and by burning their way through overlying rock, eventually these reach the surface to for explosive volcanoes
-the andesitic lava has a viscous nature this creates complex composite volcanic islands known as an island can appear
oceanic - oceanic plate boundaries
-two oceanic plates moving towards each other
-one if forced under the other and the process involved with subduction being
-the crust that is subducted may be marginally the denser of the two plates is the one which is moving more quickly
-subduction occurs in the same way as at oceanic- continental but it is less clear which plate descends
tenches and arc at oceanic- oceanic
-earthquakes are frequent: subduction process produces shallow deep focus earthquakes some of which can be very powerful and sub sea earthquakes may result in the formation of tsunamis
-ocean trenches and island arcs are the main features as the interception tales place offshore
continental - continental collision boundary
-sediments scraped off vanishing ocean floors between the plates or volcanoes associated with earlier subducted are compressed to form young fold mountain chains with deep roots in the litosphere
what is the movement of plates at a constructive boundary
two plates are moving apart leaving a gap in the middle for magma to rise up through
what are tectonic features at a constructive boundary
-volcanoes form but dont erupt with force as magma escapes easily
-rift valleys can form ad land falls down into the space left as plates move apart
what tectonic features form at destructive oceanic- oceanic
trenches and arcs
what tectonic features form at destructive oceanic - continental
-trenches
-fold mountains
-volcanoes
what tectonic features form at destructive continental - continental
fold mountains
what is the movement of plates at conservative boundary
here two plates do not directly collide but slide past each other along a fault
what are tectonic features at a conservative boundary
-fault lines
-earthquakes do occour
how long did wagner think the plate movement has taken since pangea formed
300 million years
what was found when the mid oceans were mapped
both sides of the ridge were moving apart with a symmetrical image of both sides at the ridges
what did wagener initially struggle to explain
pull and push to how it was happening
as well as climate and landscape what else proved this theory
fossils
VOLCANOES