Which type of crust is the most dense and less thick?
Oceanic crust
How thick is the oceanic crust?
5 - 10 km
What is the oceanic crust composed of?
Basalt
What are the ages of the different types of crusts?
Continental crust: Up to 4 billion years old
Oceanic crust: Up to 200 million years old
Name the two layers within the upper mantle:
Lithosphere
Asthenosphere
How are the upper and lower mantles different to one another?
The lower mantle is hotter and denser
the lower mantle is solid
the upper mantles (asthenosphere) is semi-molten magma
What is the asthenosphere?
The asthenosphere is a Semi-molten layer that constantly moves due to convectioncurrents.
Movements are powered by heat from the core
The asthenosphere moves below the lithosphere causing plate tectonics to move
The lithosphere consists of the crust and rigid upper section of the mantle
The lithosphere is broken up into 7 major plates, which move around the Earth's surface
What are the 4 main layers of the earth
A) crust
B) mantle
C) outer core
D) inner core
The inner core is a solid ball made up of iron and nickel
How hot is the inner core?
Approximately 5200 degrees Celsius
Why is the inner core so hot (5,200 degrees Celsius)?
Radioactivedecay (elements like uranium give off heat when they decay)
Pressure
The inner core is responsible for Earth's internal energy, and it spreads throughout the mantle
The outer core is semi-molten and is made out of iron + nickel
How hot is the outer core?
Approximately 4500 - 5500 degrees Celsius
Why do plates move due to the convection currents in the asthenosphere?
the convection currents push and pull the plates in different directions; making them move
Explain the cause of convection currents simply?
Temperaturedifferences in the magma create circular movements
What does this diagram show?
Convection currents in the mantle
Name 2 pieces of evidence for the plate tectonic theory.
Seafloor spreading
Distribution of earthquakes and volcanoes
What are the main 4 theories for what forces the tectonic plates to move?
RidgePush (gravitational sliding)
ConvectionCurrents
SlabPull (subduction zones)
MantleDrag (convection)
Explain how Convection Currents work:
Earth's mantel heats the inner part of the asthenosphere making it less dense and slowly rise
As it rises to the top it cools down and becomes more dense making it slowly sink
This creates circular movements of semi - molten rock which are the "convection currents"
Shortly explain how "Slab pull" causes tectonic plates to move:
Oceanic plates sink into subduction zones causing the sea floor to spread or rifts to form
In detail explain how Slab pull causes tectonic plates to move:?
At destructive margins, the new oceanic lithosphere is forced under the continental plate
As the plates sinks, gravity pulls the plate down into the mantle
This pulls slabs of plate apart
Which causes the sea floor to spread or rifts to form (plate movement)
In one word explain how "Mantle drag" causes plate tectonics to move:
Convection
In detail explain how "Mantle drag" causes plate tectonics to move:?
the very slow creep-motion of convection currents in the mantle and asthenosphere drags the overlying solid lithosphere along like a conveyor belt
Explain how "ridge push" moves plate tectonics:
Gravitational sliding
In detail explain how ridge push moves plate tectonics:?
At constructive plate boundaries magma rises to the surface to form newoceaniccrust which is very hot.
The heat from the new crust heats up other surrounding rocks causing these rocks to expand and rise above the surface of the surrounding crust forming a slope
The new crust then cools and becomes denser
Gravity then causes the denser rock to move downslope away from the platemargin
This puts pressure on the tectonics causing them to move apart <--__-->
Fill in Blank:
A) Mantle Drag
Fill in Blanks:
A) Slab Pull
B) Subducting Slab
Fill in Blank:
A) Ridge Push
Sea floor spreading:
Palaeomagnetism provides evidence that the sea floor has gradually moved apart at a mid-ocean ridge
Lava cools and solidifies with the minerals lining up with the magnetic field
The direction of the minerals on either side is a mirror image
Slab pull can only occur at destructive plate boundaries
Ridge Push can only occur at constructive plate margins
What are mid ocean ridges?
Underwatermountain ranges caused by the sea floor spreading apart
What piece of evidence for the theory of plate tectonics did Alfred Wegner find?