Hazardous Environments Flashcards
What is a hazard
An extreme event that threatens people, their property and settlements
When does a hazard become a disaster
When the hazard causes widespread destruction to property and human lives(death)
Risk
The probability of an event happening and the scale of its possible damage
Features of oceanic crust
-newer(less than 200 million years old
-denser(heavier)
-thinner(5km)
-can subduct
Features of continental crust
-older(1500million years old)
-less dense
-thick(30 km)
-cannot subduct
Ways tectonic plates move
-slab pull
-ridge push
-convection currents
Lithosphere
Top 100 km of the earth that makes up the earths tectonic plates
Asthenosphere
The rest of the upper part of the mantle that acts as a lubricant for the tectonic plates to move on
Trends in the distribution of earthquakes and volcanoes
-mostly correlate with plate boundaries
-volcanoes are three quarters around the pacific ring of fire which is a ring around the pacific
Volcanoes that aren’t on plate boundaries are called hotspot volcanoes
Features of constructive plate boundaries
-2 plates move apart, creating new crust in the middle as magma pushes its way up and solidifies
-creates effusive volcanoes and small earthquakes
Features of destructive plate boundaries
-two plates move towards each othee
-oceanic plate subducts underneath continental plate
-subducting plate melts because of high temps in the earth. Magma rises and is extruded at the surface, forming volcanoes
-creates powerful earthquakes and explosive volcanoes
Collision plate boundaries
-2 continental plates collide
–forced to buckle upwards
-causes powerful earthquakes and fold mountains. No volcanoes
Conservative plate boundaires
-2 plates slide past each other
-creates powerful earthquakes as pressure builds up between the plates then is suddenly released
How does a volcano form at a constructive boundary
-two plates move apart from each other
-magma rises to the surface at this weak spot and is extruded in eruptions
-this forms volcanoes when it solidifies to lava
-forms shield volcanoes
-also forms new land
Characteristics of shield volcanoes
Short
Gently sloping
Composed of basaltic lava
Low viscosity
Effusive eruptions
destructive boundary volcano formation
-two tectonic plates converge together
-oceanic plate subducts underneath continental plate
-oceanic plate melts
-newly formed magma rises to the surface and is erupted
-forms a volcano over time as more material is erupted, cools and solidifies to lava
-forms strato volcanoes
characteristics of strato volcanoes
-tall, steep-sided
-alternating layers of lava and pyroclastic flow/ash deposits due to sticky, high viscosity rhyolitic lava which have explosive eruptions
benefits of living near volcanoes
-jobs created(tour guides, mining
-fertile soil for farming
-geothermal energy can be used to heat homes
-valuable minerals
-tourist visit to see features like geysers, bringing money to the economy
-can create new land
negative of living near volcanoes
-risk of eruption
-risk of contaminated water
-mining can cause noise, air and dust pollution
-ash can have negative impacts on infrastructure
-destroy land during eruptions
-poisonous gases and ash erupted that are harmful and contaminate the air
why do people live in areas at risk of earthquakes
-ignorance of the risk-may not have a large earthquake in living memory
-no social memory of an earthquake having occurred
-wish to stay near relatives/where they grew up/god location etc
-people do nothing and accept the hazard
-people adjust to living in a hazardous environment (strengthening the home and preparedness)
causes of earthquakes
-plates get stuck due to friction, often caused by protrusions on the opposite plate
-pressure builds up
-pressure gets too great and plates slip. Slipping motion causes energy to be released in the form of seismic waves, which is an earthquake
precursor events of earthquakes
small tremors in preceding months
increase in radon emissions
-indicators of previous earthquakes(fault lines and seismic gaps)
Factors affecting number of deaths
-age of building/if they have been made EQ proof
-infrastructure damage
-potential for ground liquefaction
-population density
-poverty
-poor governance
-depth of focus
-strength of earthquakes
-number of aftershocks
-level of development
-time of day
-distance from epicentre
-proximity to secondary hazards(tsunamis, landslides etc)
locations of tropical cyclones
-tropical oceans 5-30 degrees N/S o the equator
-hurricanes in the Atlantic and eastern Pacific oceans
-cyclones in the Indian Ocean
-Typhoons in the western Pacific
causes of the formation of tropical cyclones
-Warm, moist air rapidly rises forming an area of low pressure
-Air from high-pressure areas rushes in to take the place of the rising air
-This air then rises forming a continuous flow of rising air
-As the air rises it cools and condenses. This releases heat energy which helps to power the tropical cyclone
-Air at the top of the storm goes outwards away from the centre of the storm
-The Coriolis force causes the rising air to spiral around the centre.
-Some of the air sinks in the middle of the storm forming the cloudless, calm eye.
-The tropical cyclone moves westwards from its source
-When a tropical cyclone makes landfall or moves over an area of cold water it no longer has a supply of warm, moist air and it loses speed and temperature. Rainfall and winds decrease
vulnearability
how susceptible a population is to a hazard
hotspot volcanoes
-location on the Earth’s surface where there are active volcanoes not on or near a plate boundary
-form due to mantle plumes
-columns of hot, molten rock that rises from deep within the Earth’s mantle, and reaches the surface in the form of an eruption
-eg hawaii
ridge push
-occurs at mid ocean ridges
-rigid lithosphere sliding down the hot raised asthenosphere under the force of gravity
slab pull
-subducting plate sinks into hot mantle beneath it
-Slab pull occurs where older, denser tectonic plates sink into the mantle at subduction zones. As these older sections of plates sink, newer and less dense sections of plate are pulled along behind. Sinking in one place leads to plates moving apart in other places.
convection currents
-magma near outer core is heated
-magma warms up and expands and becomes less dense
-less dense magma starts to rise towards the crust
-as magma nears the crust it begins to cool
-cooling magma becomes denser and begins to sink
-rising and falling magma creates circular currents with the mantle
-these currents that create friction with curst above and causes it to move
volcanic hazards
-lava flows
-pyroclastic flow
-lahars
lava flows
-extremely hot so can cause severe burns and often burn down vegetation and structure
pyroclastic flow
-people can be killed by pyroclastic flows
-try travel fast so people cannot outrun them
-they are burnt to death or chocked to death
lahars
-specific kind of mudflow made up of volcanic debris
-formed from rapid melting of snow and ice during an eruption
-heavy rainfall on loose volcanic debris
-flow like liquids
predict
prediction is knowing an event is shortly about to take place
prepare
finding about ways to reduce possible impacts of earthquakes and tsunamis
recovery
-involves deciding what needs to be done to restore disaster area back to normal
appraise
-looking at disaster and assessing how well or otherwise the emergency operations worked
how can developed countries prepare for earthquakes
-training/educating people
-emergency drills
-availability of emergency kits
-earthquake proof building design
-roads and bridges specially strengthened
how can short term relief help reduce impacts in a developing country
-management of local water supplies so sanitation conditions are improved
-use of emergency aid to help people with injuries so treatment of people can save lives
-donating food and shelter to affected people so they are protected from exposure and weather conditions
-burying any dead who suffered from the collapse of buildings to stop spread of disease
How can tropical storms be a threat
-high wind speeds damage buildings and people
-heavy rainfall causes flooding
-strong winds can cause storm surges and flood coastline
-vegetation damaged
Measure of tropical cyclones, earthquakes and volcanoes
Earthquake:
Richter is energy released
Mercalli scale is damaged caused
Tropical Hazard:
Saffir Simpson is wind speed
Volcanoes:
Volcanic Explosivity Index is size of ash cloud and other impacts
Why is the coriolis effect needed for tropical cyclones
-force created by Earth’s rotation that deflects moving objects at the Earth’s surface, causing it to spin
NA, CS: northern hemisphere is anticlockwise, southern hemisphere is clockwise.
Sodium and Caesium
Examples of building designs to mitigate risks of earthquake
-steel frames that sway during the earth movement add rubber shock absorbers in the foundation, less likely to create debris and collapse
-buildings can be retrofitted with wire mesh to strengthen buidlings
-base isolation so the building moves separate to the ground
-counter weight
-strict building codes so buildings are built to reduce movement during an earthquake, less likely yo collapse
-strengthen windows, shut windows when earthquakes happen so glass does not enter home as shutter blocks it
Conditions for tropical hazards
-warm water to a depth
-rising water as a result
-low wind sheer (wind from other direction)
-coriolis effect from a latitude: rotation of the earth leads to the deflection of air causing it to spin
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