Tectonics: 1.3 Physical processes explain the causes of tectonic hazards…
Tectonics: 1.3 Physical processes explain the causes of tectonic hazards
Explain how P, S and L waves cause crustal fracturing, ground shaking and secondary hazards such as liquefaction and landslides.
The fastest (rate of about 8 km/sec) so they arrive fast
Cause the least damage
They are vibrations caused by compressions
Shake the ground vialently causing damage
Arrive next (about 4 km/sec)
Arive last, as they only travel on the surface - 'vibration occurring in the horizontal plane'
Thye have a large amplitude and cause significant damege, including fratucring the ground surface
Explain how volcanoes cause lava flows, pyroclastic flows, ash falls, gas eruptions, and secondary hazards such as lahars, jökulhlaup.
Extensive areas of solidified lava, which can extend several km from volcanic vents if the lava is basaltic and low viscosity. Can flow up to 40km
Very large, dense clouds of hot ash and gas at temperatures of up to 600’. They can flow down the flanks of volcanoes and devastate large areas.
Ash particles can blanket huge areas in ash killing vegetation collapsing buildings and poisoning water.
The eruption of co2 and sulfur dioxide which can poison people and animals in extreme cases.
Volcanic mudflows, which occur when rainfall mobilises volcanic ash. They travel at high speed down river systems and cause major destruction (occur at subduction zones).
Devastating floods caused when volcanoes erupt beneath glaciers and ice caps, creating huge volumes of meltwater. They are common in Iceland (occur on constructive plate margins).
Explain how tsunamis can be caused by submarine earthquakes
Tsunamis are mostly generated when a sub-marine earthquake displaces the sea bed vertically as a result of movement along a fault line at a subduction zone. However, they can also be generated by landslides and volcanic eruptions.
The violent motion displaces a large volume of water in the ocean water column, which then moves outward in all directions from the point of displacement.
Submarine earthquakes that occur close to shorelines can generate intense ground-shaking damage, followed by damage from the subsequent tsunami.