Tectonic Processes And Hazards Flashcards
(21 cards)
How do convection currents cause plate movement?
•The Earths mantle is hottest close to the core so the lower parts of the athenosphere heat up, become less denser and slowly rise.
•As they move towards top of athenosphere, they cool down, become denser and sink.
•These circular movements of mantle is known as convection currents.
•Convection currents create drag on the base of tectonic plate, causing them to move.
4 types of plate margins
Destructive, collision, constructive, conservative
Destructive plate margin
•Denser oceanic crust is subducted under the less dense continental crust, forming a deep sea trench
•Oceanic crust is heated by friction which melts into magma.
•Magma is less dense than crust above it, so it rises up and volcanoes form on surface.
Collision plate margin
•2 pieces of continental crust have same density therefore neither is subducted.
•2 pieces of continental crust fold up against each other, forming fold mountains
Constructive plate margin
•Magma rises in the mantle below causing 2 of the same crusts to diverge.
•Magma rises to fill gap created, then cools to form new crust.
•New crust is dragged apart aka sea floor spreading forming mid ocean ridges.
•Similar process of spreading occurs at land margins forming rift valleys
Conservative plate margin
•2 pieces of crust slide past each other either in same or opposite direction at different speeds.
•This movement leads to increased friction leading to pressure building up and causing an earthquake.
How do earthquakes form?
•When plates jolt past each other at plate boundaries, they send out seismic waves which carry energy
•The pressure that is released can cause crustal fracturing.
•The crust has a degree of elasticity which allows it to recoil back and forth.
•Produces sensation of ground shaking aka earthquake
2 factors that affect strength of earthquake and how
•Type of plate margin - destructive plate margins cause higher magnitude earthquake than constructive plate margins.
•Depth of focus - Shallow focus earthquakes do more damage than deep focus earthquakes.
How do landslides occur
•When the shaking of the ground dislodges rocks and soil
How do tsunamis occur
•Submarine earthquakes cause sea floor to move quickly which displaces water and cause waves
•As waves approach coast, they lose energy and slow down due to friction with the rising sea bed.
•Causes waves to grow in height
Mantle plumes
•Vertical columns of extremely hot magma that rises up from mantle
•Heat from mantle plume melts part of the crust above, which creates large volumes of magma
What lava forms at constructive plate margins? How hot, silica content, viscosity, eruptions, forms what
•Basaltic lava is very hot (1000 to 1200 degrees) low silica content
•Has low viscosity (runny) so it flows easily and quickly.
•Eruptions are frequent and go on for a long time and less violent
•Forms shield volcanoes
What lava forms at destructive plate margins? How hot, silica content, viscosity, eruptions, forms what
•Andesitic and rhyolitic lavas are cooler (650 to 1000 degrees) high silica content
• Has high viscosity so they flow less easily
•Eruptions are short lived but more violent
• Forms composite volcanoes
Hazard
Potential threat to human life and property
Disaster
When a hazard occurs and has a significant impact on a population
The Degg model
•Suggests that a disaster occurs when a natural hazard event meets a vulnerable population.
•The greater the natural hazard event, the more vulnerable the people therefore the greater the disaster
Risk
The potential exposure to a disaster
Pressure and release model
•Root causes of vulnerability can create dynamic pressures leading to unsafe conditions when a hazard occurs.
•The more vulnerable the population is, the greater the risk of disaster for the population
Magnitude
Size and intensity of a natural hazard
Hazard profile
Magnitude, speed of onset, duration, frequency, spatial predictability, areal extent
Hazard Management Cycle
Preparedness > Response > Recovery > Mitigation
