The structure of the Earth Flashcards
How thick is the Earths crust on average?
20km thick
What is the lithosphere?
The crust and the upper/ rigid section of the mantle
What is the asthenosphere?
The upper part of the mantle (the boundary between the earths crust and mantle)
What causes the movement of plates?
convection currents
What is the outer core made up of?
molten iron and nickel
What is the inner core made up of?
solid iron and nickel
The cores temperature is over how many degrees celcius?
5000
What is primordial heat?
heat left over from the earths formation
What is radiogenic heat?
heat produced by radioactive decay of isotopes
Approximately how thick is the earths lithosphere?
approximately 80-90km thick
What is Mohorovicic Discontinuity?
semi-molten (plastic-like) rock that can move very slowly
How thick is oceanic crust?
6-10km thick
How thick is the continetial crust?
30-70km thick
Which is more dense oceanic or continential crust?
Oceanic
What crust can be subducted?
Oceanic
Which crust cant be renewed or destroyed?
Continential
How old is the oceanic crust?
less than 2 million years
How old is the continental crust?
over 1500 million years
What is the oceanic crust made out of?
Basalt
What is the continential crust made out of?
Granites/ sedimentary rock
What crust moves faster?
Oceanic
What are the rules for plate movement?
-Plates cant overlap
- No ‘gaps’ can occur on the surface
- As new crust is created, it must be destroyed somewhere else
-Very little change occurs in the middle of plates
How quick is plate movement?
Very slow but continuous approximately 5-10 cm per year
How do convection currents occur?
- the earth core radiates heat so the semi-molten lower mantle becomes less dense
- as a result it rises
- then it drags the plates along due to friciton
- eventually the magma cools and becomes denser
- then the dense, cool magma sinks back to the core
- this repeats
