Year 11 Plate Tectonics Flashcards
Crust
Solid, hard outer shell
Mantle
Soft molten rock about 3800*C
Outer core
Liquid iron and nickel
Inner core
Combination of nickel and iron, solid, up to 5500*C
How do we know about the different layers that exist
Because the seismic waves are refracted and travel at different speeds which gives us an image
Continental crust: Where? Thickness? Density? Age? Rock type?
Lies under continental land masses
25-100km thick
less dense, doesn’t sink
3-4 billion years old
new crust never formed and can’t be destroyed
Granite with large crystals, as rock cools slowly
Oceanic crust Where? Thickness? Density? Age? Rock type?
Lies under oceab
5-10km thick
more dense, sinks into mantle when meets continental
Oldest only 180 million years old
Constantly formed at constructive boundaries where it’s destroyed
Basalt with small crystals as cools quickly
What are tectonic plates
Large sections of the Earth’s crust able to move separately from each other
Conservative margin: what? Earthquakes? Volcanoes? Example
Plates more past each other, Earthquakes, no volcanoes e.g. Haiti Earthquake 2010 American and Caribbean
Constructive margin: what? Earthquakes? Volcanoes? Example
Plates move apart, earthquakes and volcanoes e.g. Iceland, Eurasian and n’ American
Destructive margin: what? Earthquakes? Volcanoes? Example
Plates moving together, earthquakes and volcanoes e.g. Chile earthquake 2010 Nazca and s.American plate
Why do plates move
Convection current, as magma heated it rises, as it rises it cool so sinks again causing the plates above to move
What’s ridge push
As the lithosphere cools, it becomes denser and starts to slide down, away from the ridge, causing the plates to diverge
What’s slab pull
At destructive margins, the denser plate subducts down into the mantle due to gravity/ This motion pulls the rest of the plate along with it
What happens at constructive plate boundaries
As plates slowly move apart, magma rises to earth’s surface, it cools and solidifies forming new igneous rock. Eventually rock builds up forming a shield volcano, some so large they form islands such as Iceland
What happens at destructive plate boundaries (continental and oceanic)
Oceanic plate denser so forced beneath continental, know as subduction zone. As subducted, it melts forming magma and earthquakes triggered. Magma collects and rises up through cracks, building up pressure, triggering volcanic eruptions. Fold mountains formed at subduction zones e.g. Andes
What happens at destructive plate boundaries (oceanic and oceanic)
The older, denser oceanic slap is force under the other, creating a trench at subduction zone. Volcanoes formed and earthquakes, same as c+o e.g Pacific and n.American plate
What’s the Pacific ring of fire
An area of high seismic and volcanic activity around the Pacific ocean. There are many destructive margins around the Pacific plate which creates tectonic activity
What happens when two continental plates converge
Both plates have the same density so both pushed upwards forming mountain ranges. Magma can’s penetrate the thick crust so no volcanoes. The collision of the plates cause many earthquakes such as Himalayas
What happens at conservative plate boundaries
Occurs when plates slide past each other in opposite or same direction but at different speeds. Friction is eventually overcome and the plates slip past in a sudden movement causing an earthquake e.g. San Andreas fault
Name the point in the crust where the pressure is released
Focus
What is the epicentre
The point on the Earth’s surface above the focus where the most intense shaking occurs
Factors affecting the impact of an earthquake
Level of development
Richer LICs and NEEs more likely to have the resources and technology for monitoring and prediction
Factors affecting the impact of an earthquake
Population density
More densely populated the area, the greater the hazard will be so more deaths and casualties
Factors affecting the impact of an earthquake
Communication
Accessibility for rescue teams, earthquakes often damage bridges etc
Factors affecting the impact of an earthquake
Time of day
This influences weather people are in their homes, at work or travelling if during rush hour could be devastating
Factors affecting the impact of an earthquake
Time of year and climate
Will influence survival rates and the rate that disease is spread. Hot tropical places are particularly bad
Richter scale
Measures the magnitude of a tremor using seismograph, has no upper limit, is a logarithmic scale so each is 10x larger than the previous
Mercalli scale
Scale from 1-XII and measures the effects of earthquakes. Uses subjective descriptions of the resulting damage
Chile earthquake Date/ GDP ranking magnitude focus depth epicentre cause
27th February 2010 46 8.8 35km 11km from Concepcion Nazca plate and s. American plate (convergent)
Haiti earthquake Date/ GDP ranking magnitude focus depth epicentre cause
12th January 2010 143 7.0 13km 25km west of port-Au-prince Caribbean plate and north American plate (conservative)
Deaths, injuries, no. of homes damaged- Chile
500 deaths, 12,000 causalities, nearly 400,000 homes damaged
Deaths, injuries, no. of homes damaged- Haiti
230,000 deaths, 300,000 casualties, 250,000 homes damaged
Secondary effects- Chile
150 deaths from Tsunami,
est $15-30 billion damage
Lost power, fire at chemical plant
Secondary effects- Haiti
All hospitals in the capital were destroyed, public phones not available
Looting, debris blocked main road
2 million left without food and water
Short term response- Chile
Government vowed to deliver aid quickly Firefighters combed rubble for people Army sent 10,000 troops, curfew imposed to prevent looting Communications in the capital restored within 4 days
Short term response- Haiti
Government appealed quickly for aid
Over 1st weekend received many food and water packets
Hard to get aid as the port was damaged
Long term response- Chile
Month later, government launched a housing reconstruction plan
Strong economy so could rebuild without relying on foreign aid
Long term response- Haiti
Dominican republic accepted some refugees
Senegal offered land to anyone in Haiti who wanted it
Preparation and protection- Chile
Building code require shake-resistant construction and rapid emergency response
Regular anti-disaster drills
Prepared following 1960 earthquake
Preparation and protection- Haiti
Tsunami warning was issued immediately after initial earthquake, but quickly cancelled it
Not prepared as never had an earthquake before
Port-Au-Prince had 2.5 mil population so overcrowded and houses were poorly built
