TECTONICS Flashcards
what is a natural hazard
naturally occurring event with the potential to cause loss of life/property.
what is a natural disaster
when the natural hazard causes social, economic and environmental damage.
vulnerability
people’s ability to cope with hazard events
what does vulnerability depend on
how exposed to the hazard the population is. how susceptible to human and/or economic loss because of where they live
case study Nepalese earthquake
- date= 25 April 2015
- magnitude=7.8
- half its population living in poverty
- infrastructure severely damaged(not built to withstand natural disaster)
- is mountainous= many landslides=rescue is difficult
- emergency services unable to cope
- tourism fell=unemployment
deggs disaster model
overlap of hazard and vulnerability causing disaster
constructive/divergent plate boundaries
plates moves apart forming new crust
mid ocean ridges
an elevated region with a central valley on an ocean floor at the boundary between two diverging tectonic plates where new crust forms from upwelling magma.
rift valleys
A rift valley is a lowland region that forms where Earth’s tectonic plates move apart, or rift. Rift valleys are found both on land and at the bottom of the ocean, where they are created by the process of seafloor spreading. where the land between two continental/oceanic plates collapses.
destructive/convergent plate boundaries
plates move towards each other where the lighter /less dense plate subducts
subduction
the movement of the less dense plate sliding under the denser plate
oceanic plates are usually more denser than continental plates
oceanic plate-continental plate
oceanic plate subducts creating fold mountains, where plate collision forms folding.
constant movement=continuous folding=increase friction in Benioff zone. magma pushes through gapes creating explosive volcanic eruptions
oceanic plate-oceanic plate
lighter plate subducts, deep ocean trenches and volcanoes form. submarine volcanoes grow to form island volcanoes(island arcs).
shallow deep focus earthquakes occur
Benioff zone
area where friction is created between colliding tectonic plates , resulting in intermediate and deep earthquakes
continental-continental
collision margin occurs forcing rock upwards forming high mountains e.g Himalayas. =no volcanic activity and earthquakes are shallow focus
conservative boundaries
2 plates slide past each other.(move parallel towards each other in opposite directions.)form transform fault. no volcanic activity. friction creates powerful earthquakes . at points where plates get stuck to each other stress is built up. the longer the stress is built up the greater the magnitude of the earthquake.
Collison margin
If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. This is called a collision margin.
How are earthquakes caused
formed along plate boundaries
friction between plates causes pressure to build up release of this stress/pressure causes earthquakes at different magnitudes
explain and name the 3 types of seismic waves
- P WAVES(primary)= are the fastes waves, move through solid and liquid. moves forwards and backwards creating expansions and compressions. least damaging
- S WAVES(secondary)= moves slower than p waves. moves through solids only. moves in a sideways motion at right angles to direction of travel. more damaging than p waves.
- L WAVES(love)= moves slowest. last to arrive. Shake ground side to side . most damaging. are larger. and focus most of its energy onto earths surface.
what are seismic waves measured by
seismometer
primary impacts of earthquakes
- crustal fracture
- building / infrastructure collapse/damage
- ground shaking
secondary impacts of earthquakes
- liquefaction, surface of rocks acts more like a liquid than solid during movement, causing building + roads to sink +power and gas lines to break causes fires.
- Landslides/avalanches,
- tsunami-cause coastal flooding
loma prieto earthquake -case study
date-17 October 1989 magnitude- 6.9 location- san Francisco -Loma Prieto built on soft sand- liquiefaction-buildings and roads collapsed caused 42-67 earthquake related deaths
aftershocks of eartyhquakes
larger earthquakes= more aftershocks
cause more damage to building structure= more possible death=more economic environmental damage.
Aftershocks are smaller earthquakes that occur in the same general area during the days to years following a larger event or “mainshock.”
