Tectonic Processes And Hazards Flashcards
(22 cards)
Convergent plate
. Denser oceanic crust is forced underneath the continental rust. This is know as slab pull
. Deep trench forms where oceanic plate is pushed under
. Composite volcanoes
. Tsunamis
. Earthquakes
Divergent
. Magma rises and seeps through the gap created as the plates move apart
. A ridge underwater
. Volcanic mountains
. Earthquakes
Collision
. Plates of similar weight collide and force upwards
. Built up of pressure suddenly releases
. Earthquakes
. Fold mountains
Conservative
. Plates rub against eachorher because they’re going at different speeds causing friction
. Release of friction causes fault lines in the ground
. Fault lines
. Earthquakes
Hotspots
. Occur in centre of plates where there is a hot mantle plume rising to surface that triggers the coast
Why do plates move?
Heat rises and falls, pulling the plated apart and making them move. This is done using convection currents
Tsunamis
. Triggered by an earthquake which occurs under an ocean
. When plate jolts, ocean above is forced upwards providing extra energy to the waves
Time of evidence supporting plate tectonics
. 1915: fossils collected by Wegener
. WW1: Found geologic features on ocean floor
. 1919: proposed concection currents exist
. 1946: ocean floor is mapped with solar technology
. 1954: first world mapf of volcanic eruptions is published
. 1960: hess and Dietz develop theory of sea floor spreading
. 1963: magnetic Rock reveals pattern of spreading away from centre of Atlantic ocean
. 1965: Wilson proposed idea that earth’s crust made of plates
. 1983: first gps made available
Shockwave body
. Two types- primary and secondary
. Travel through interior of earth’s layers
. Primary- faster but not felt
. Secondary- slower and do most damage
Shockwave surface
. Two types- love and Rayleigh
. On the surface and cause the most damage
. Love are transverse
. Rayleigh push ground forward and back
. Only found on shallow earthquakes
Secondary earthquake impacts
. Tsunamis
. Landslides
. Liquefaction
. General groun displacement
Volcanic explosivity
. Has a range from gentle fissures to explosive composite areas
. Links to energy of eruption
. Supervolcanoes are the largest
. Basaltic and andesitic
. Use of volcanic expolsivity index
Secondary volcano impacts
. Jokulhoup- flood causes by melted glacier
. Lahars- water mixed with volcanic deposits
. Most significant things involve water
Basaltic lava
. Hottest (1000-1200)
. Low gas content
. Thin and runny
. Gentle
. Location: ocean hot spots, mid ocean ridges and shield volcanoes
Andesitic lava
. Temp: 800-1000
. Gas content 3-4%
. Slow flow
. Violent eruption
. Location: composite cone volcanoes
Rhyolitic lava
. Temp: 650-800
. Gas content 4-6%
. Thick flow
. Violent eruption
. Location: super volcanoes
Primary volcanic impacts
. Lava flows
. Pyroclastic flow
. Tephra and ashfall
. Gas eruption
Secondary volcanic impact
. Lahars
. Jokulhoup
How are tsunamis formed
. Caused by large underwater earthquakes along subduction zones
. Energy released during earthquake causes sea floor to uplift, displacing the water column above
. This displaced water forms the tsunami wave
Difference between a disaster and hazard
Disaster- a hazard becomes a disaster when 10 or more people are killed and/or 100 or more people are affected
Hazard- a perceived natural/geophysical event that has the potential to threaten both life and property
Why do people remain exposed to hazards?
. Unpredictability
. Lack of alternatives
. Changing levels of risk
. Russian roulette (optimistic it won’t happen to them)
. Cost vs benefit
Define hazard vulnerability
The capacity of a person or group to anticipate, cope with, resist and recover from the impact of a natural hazard
