How different hazards occur Flashcards
(28 cards)
Where do EQ’s occur?
On plate boundaries
Define plate boundary
Where different plates meet
What is a plate?
Areas of land that the lithosphere is divided up into.
How do EQ’s occur at destructive plate boundaries?
Subduction Range of EQ types Pressure compressing as they meet suddenly releasing focus Epicentre C & O, C&C, O&O Fold mountains Shallow high damage
How do EQ’s occur at constructive plate boundaries?
Shallow, low magnitude
Magma rises
Most submarine so little risk to people
How do EQ’s occur at conservative plate boundaries?
Frequent shallow
Sometimes high mag
EQ within plate
From stress on land due to dam/reservoir building
What are the primary impacts of EQ’s?
Ground movement, seismic waves, collapsing infrastructure
What are the secondary impacts of EQ’s?
Soil liquefaction, landslides, avalanches, tsunamis
How do volcanoes occur at constructive boundaries?
Shield - thin, runny, frequent, gentle
Mostly at oceanic ridges
Mostly on sea floor so not major hazard unless they emerge above sea level to form island = more dangerous
How do volcanoes occur at destructive boundaries?
80% in Ring of Fire
At subduction zones
Composite - pyroclastic, lava & ash, hot, viscous, dangerous
Define mid ocean ridge
Seismically active submarine ridge system in the middle of ocean basin where there is upwelling magma
Define Ring of Fire
Area in Pacific Ocean basin where many EQ’s & volcanic eruptions occur
Define Hotspot
Localised area of Earth’s Crust with unusually high temperature
Define pyroclastic flow
Destructive dense mass of hot ash, lava, gas ejected explosively from a volcano and quickly flowing
Define magma
Molten material rising towards Earth’s surface when hotspots in asthenosphere generate convection currents
What are the impacts of volcanoes?
Lava flows, pyroclastic flows, ash falls, tsunami, mudflows
What increases the chance of a landslide?
In mountainous areas, where there is heavy rain, seismic areas, deforestation increases chance
What increases the chance of a snow avalanche?
Mountainous
Slopes steeper than 35 degrees
Global warming
What are the causes of drought?
Variations in movement of the ITCZ
El Nini
Mid latitude depression track changes
Anticyclones
Define ITCZ
Inter-tropical convergence zone - area of low pressure as northeasterly & southeasterly winds converge over the equator forming clouds and frequent heavy showers
Define mid-latitude depression tracks
Where sub-tropic warm air meets polar cold air creating low pressure = rainfall/cyclones
What are the causes of flooding?
Series of depressions Monsoon cyclones Flash floods El Nino Rapid snowmelt adding water to already swollen river systems
What are the causes of storms?
Tropical cyclones
Tornadoes
Mid latitude storms
What are the hazards that occur as a result of storms?
High wind velocity Storm surges Coastal flooding Flood Mudslides
