Plate tectonics (KQ1) Flashcards
(31 cards)
What is the internal structure of the earth made up of?
- crust
- lithosphere
- mantle
- aesthenosphere
- core
What is the outermost layer of the earth made up of?
- basalt
- granite
How thick is the outermost layer of the earth?
- varies from a few km to more than 70km thick
What is the lithosphere made of?
- crust
- uppermost mantle
What is the mantle made up of (other than lithosphere)?
- aesthenosphere
- mostly solid rock that flows under high temperatures and pressure
How thick is the mantle?
- about 2500km thick
What is the temperature of the mantle?
- between 800 to 3000 degrees celsius
What is the core made up of?
- iron
- nickel
- separated into liquid outer core and solid inner core
How thick is the core?
- about 3300km thick
What is the temperature of the core?
- between 3000 to 5000 degrees celsius
What are the two different types of crust?
- oceanic
- continental
Where is the oceanic crust located?
- beneath deep oceans
Where is the continental crust located?
- beneath the earth’s land masses
- under shallow seas close to continents
What are some characteristics of the oceanic crust?
- denser (basalt)
- thinner (between 5-8km)
What are some characteristics of continental crust?
- less dense (granite)
- thicker (35-70km)
Why do tectonic plates move?
- plate movement is caused by a combination of convection currents and slab-pull force
- movement of convection currents refer to the movement of heat within the mantle
How do convection currents cause plate movement?
- as the mantle is heated by the core, the material expands, rises and spreads out beneath the plates
- this pulls the plates apart as they are dragged along
- as mantle material spreads further, it cools and sinks, pulling the plates along
- the sinking mantle material heats up again as it nears the core, repeating the entire process
How does slab-pull force cause plate movement?
- as denser oceanic plates sink at the subduction zone, it pulls the rest of the plate
- this process is known as slab-pull force (pulling force exerted by a dense oceanic plate plunging into the mantle due to its own weight)
What happens when oceanic-oceanic plates diverge?
- magma rises from the mantle to fill the gap between the plates as they diverge
- a new seafloor is formed when lava flows out onto the seafloor and then cools and solidifies (seafloor spreading
- it then forms a mid-oceanic ridge
What are some characteristics of divergent oceanic-oceanic plate type?
- newly formed (youngest) rocks are closest to the middle of the ridge
- at various points along the ridge, magma builds up above the ocean to form volcanic islands
What are some examples of landforms caused by 2 oceanic plates diverging around the world?
- iceland
- mid-atlantic ridge found in the middle of the atlantic ocean
What happens when continental-continental plates diverge?
- when plates diverge, they are stretched
- this causes fractures at the plate boundary
- the land in between the 2 continental plates then sinks to form a linear depression (rift valley)
- this divergence can cause continents to break apart
What are some examples of landforms around the world caused by continental plates diverging?
- East African Rift Valley
What happens when 2 oceanic plates converge?
- denser plate subducts beneath the less dense plate
- a deep oceanic trench is formed at the point of subduction
- subducted oceanic plates causes the mantle material above it to melt, forming magma
- magma rises through the cracks to form a volcano and eventually, a chain of islands
- earthquakes may occur due to friction
