Plate Tectonics Flashcards
What is the basic structure of earth
Inner core
Outer core
Mantle
Crust
Inner core
6000 degrees, solid ball containing iron and nickel
Outer core
Semi molten lager containing iron and nickel
Mantle
1000-3500 degrees
Around the core
Mainly silicate rocks
Rigid layer then semi molten then another rigid layer on top
Crust
Outer layer
Most rigid
Two types continental which is thicker and oceanic which is thinner and more dense
3 theories about how tectonic plates move
Convention currents
Slap pull
Ridge push
What are convection currents
Asthenosphere in the mantle heat up because close to core, less dense and slowly rise
as they move up, they cool and more dense sink again
these circular movement of semi molten rock create drag on the base of tectonic plates causing them to move
What is slap pull
At destructive plate margins, denser crust is forced under less dense crust
Sinking of the plate edge s the rest of the plate towards the boundary
What is ridge push
Also known as gravitational sliding
At constructive plate margins, magma rises to the surface and forms new crust which is hot
Heats surrounding rocks which expand and rise above surface forming a slope
New crust cooks and becomes denser, gravity causes denser rock to move downslope
Puts pressure on plates causing them to move apart
What is sea floor spreading
As plates diverge, magma rises to fill gap then cools to form new crust
Over time new crust is dragged apart and crust formed again
Means sea floor is getting wider, creates mid ocean ridges
What are constructive margins
2 plates diverging away from each other
When they move pressure is released, causing mantle to melt producing magma which is less dense so it rises = volcanic eruption
Plates don’t move in uniform way, different speeds- pressure building up, plate cracks = earthquake
2 landforms constructive margins make
Examples
OCEAN RIDGE- when diverging plates are underwater
Example - mid Atlantic ridge between Eurasian and North American plate
Underwater volcanoes form at mid ocean ridges can go above sea level
Example - Iceland is formed by these
RIFT VALLEY - plates diverse beneath land, rinsing magma chases crust to bulge and fracture = daily lines. Plates keep moving, crust between parallel faults drop!!
Example - East African rift system, from Mozambique to Red Sea, often find volcanoes here eg Kilimanjaro and mount Kenya are Odin here
3 types of destructive margins
Ocean - continental
Ocean - oceanic
Continental - continental
What is a destructive margin
When 2 plates converge and move towards each other
What happens at ocean - continental plate margins
CC+OC converge, ocean more dense so is forced under, this is subduction
Forms deep sea trench and fold mountains
Volcanoes - oceanic crust is heated by friction and contact with upper marble, which melts into magma, less dense than CC and risers to surface
earthquakes - one plates moves under the other , pressure builds up, plates jerk and past each other
