earthquakes and volcanoes Flashcards
name the 4 different plate tectonic movements
constructive
conservative
destructive
colission
describe constructive plate margins
2 continental plates move away from eachother which creates a gap in the crust and allows magma to flow through
can cause both earthquakes and volcanoes
describe destructive plate margins
oceanic subducts (sinks) under continental due to oceanic being denser-> generate friction -> convection currents created -> create fold mountains and trenches -> can create noth earthquakes and volcanoes
describe collision plate margins
plates move towards eachother which creates fold mountains and earthquakes
describe conservative plate margins
plates grind past eachother in opposite directions
-cause only earthquakes
what 2 plate margins create volcanoes
destructive and constructive
how do volcanoes form at distructive margins
1- denser oceanic plate is forced under the contenental plate
2-friction and pressure cause cracks to form
3- margma rises through the cracks and creates a higly explosive volcano
what are the 3 different types of volcanoes
-strato (steep and cone shaped)
-volcanic hot spots (abnormally hot,thin crust)
-shield volcano (broad,gentle slopes)
how do volcanoes form at constructive boundaries
-convection current causes plates to move apart
-tectonic plates split
-magma explodes due to amount of pressure
what is pyroclastic flow
a mix of rock,gas and ash that travel repidly out of a volcano
what is ash
mixture of rock minerals and glass particles which can travel thousands of miles by wind
what are volcanic bombs made of
dried lava that cools after it leaves a volcano
what are lahars
when ash water and ice mix and create a river of mud
whats the case study for volcanoes in a developing country
mount st helens
what were the causes and effects of mount st helens errupting and when did it happen
-strato volcano erruoted on may 18th 1980
-causes:destructive margin in north american plate, series of small earthquakes
-effects: landslides,pyroclastic flow,57 dead, lake full of debris
why do some people chose to live next to a volcano
-fertile soil for agriculture
-attracts tourists which provides job oppourtunities
-naturally hot water-reduced cost
how can volcanoes be predicted
increase in gasses
deformed mountains
increase in ground pressure
seismic activity (earthquakes)
what are the 4 things can cause earthquakes
-> focus - where the earthquake starts (pressure point)
-> epicenter - directly above focus, where the crust is impacted
-> plate boundary
-> seismic waves
what are the 2 scales used to measure eathquakes
-ritcher scale (measures magnitude of earthquakes)
-mercaili scale (seismic activity scale which predicts the effects of the earthquake)
when did the hati eathquake happen and for how long
january 12th 2010
35 seconds
what were the causes of the hait eathwquake
-epiccenter is captial (port au prince)
-magnitude 7 earthquake
-densley populated country withh poorly structured houses
-corrupt gov
what were the impacts of the hati earthquake
-30k dead 1 mill homeless
-buildings collapsed and blocked roads which caused ambulences to arrive late
-ptsd
-damaged sea ports which damaged hatis economy
what were the responses to hatis earthquake
-senigal offered land to any hatians
-1.1b collected from charities but only 2 percent released due to corrupt gov
-USA send aid
how can we reduce impatcs of earthquakes
-earthquake proof buildings that can easily sway
-triangle strctured buildings
-earthquake drills in schools
-seismographs for preperaition
