TECTONIC HAZARDS EQ1🌋 Flashcards
define hazard
a perceived natural or geophysical event that has the potential to threaten both life and property.
earthquake case study (1)
The nepalese earthquake
when was the nepalese earthquake
25th of april 2015
what was the magnitude of the nepalese earthquake
7.8
how many injuries and deaths in the nepalese earthquake
8633 deaths over 21,000 injuries over 3 million people were made homeless
how much did the nepalese earthquake cost
They lost US$5 billion from its GDP (25% of its total) rebuilding cost : US $6.6billion NEPAL WILL NEED TO RELY ON FOREIGN AID
where is nepal located
southern asia between india and china . Nepal sits on a fault line between the indian and eurasian tectonic plates.
define a disaster
where a natural hazard causes social , environmental and economic damage it becomes a natural disaster. e.g when a vulnerable population can’t cope using its own resources
define vulnerability
people’s ability to cope with hazard events . the greater the hazard and more vulnerable the people the greater the disaster
what were the impacts of the nepalese earthquake on the 25th of april 2015
- Nepal is mountainous . The shaking caused landslides making rescue and aid efforts difficult in rural areas - Over 100 after shocks followed the initial earthquake causing more destruction and deaths making recuse work dangerous -many buildings collapsed in the capital kathmandu because they weren’t built to withstand earthquakes -The country’s infrastructure eg roads and water supplies were severely damaged - tourism fell after the earthquake putting people out of work -nepal’s emergency services were unable to cope and relied on over seas countries and aid agencies
how many layers does the earth have
three
what are the three layers of the earth
core mantle crust
what is the core of the earth
the most inner part (inner and outer core) inner core - solid centre made of mostly iron hottest part about 6000° outer core -semi molten mostly liquid iron and nickel temp of 4500°-6000°
what is the mantle
the widest layer of the earth surrounding the core . upper mantle is solid , below it the rock is semi molten forming the asthenosphere
what is the crust
the outer shell of the earths layers two types are oceanic and continental oceanic - thin - dense - 6-10Km thick-forming ocean floors continental -thicker - less dense - 45-59km thick - make up land masses
what are the 4 processes that drive plate movement / tectonic movement
mantle convection sea floor spreading subduction slab pull
what makes up the lithosphere
The crust and upper mantle make up the lithosphere
explain how mantle convection /convection currents cause plate movement
Originally thought this was the main theory however it’s much less accepted now: Heat produced by radioactive decay in the core heats the lower mantle creating convection currents within the asthenosphere,causing plate movement.
explain how sea floor spreading causes plate movement
Huge mind ocean ridges form when magma is forced from the asthenosphere and hardens forming new oceanic crust . This sea floor spreading pushes tectonic plates apart
evidence for sea floor spreading
the age of the sea floor gets progressively older with the distance from the mid ocean ridge PALEOMAGMISTISM - a record of changes in the earths magnetic fields . When lava solidifies and forms new rock the iron in it reflects the earths magnetic core and lines up with the earths magnetic direction. Mid ocean ridges show the patterns of magnetic direction mirrored on each side of the ridges
Explain how subduction causes plate movement
as two plates move towards eachother , one slides into the mantle into the subduction zone
what are plate boundaries
plate boundaries form where two tectonic plates meet
explain how slab pull causes plate movement
slab pull is increasingly seen as driving plate movement . newly formed oceanic material at mid ocean ridges becomes denser and thicker as it cools . causing it to sink into the mantle , pulling the plate down.
what are the three plate boundary types
divergent convergent conservative/transform
what are divergent plate boundaries
-constructive plates MOVE APART
why do plates move apart in divergent - constructive plate boundaries
SLAB PULL SEA FLOOR SPREADING
what is the type of magma at divergent - constructive plate boundaries
BASALTIC LOW viscosity LOW silica / gas content runny less viscous lava forms SHIELD flat volcanoes
do earthquakes occur at divergent - constructive plate boundaries
they can occur but are quite small this is because there is no friction or pressure building up over time as they are moving apart not towards eachother
what are convergent - destructive plate boundaries
where two plates COLLIDE
what causes plate movement in convergent - destructive plate boundaries
SLAB PULL - forces subduction of oceanic plate because it is denser , under the continental plate as the plate is pulled by slab pull into subduction zone . pressure and friction from the plate movement and heat from the mantle start to melt the oceanic plate forming magma.