A LEVEL GEOGRAPHY UPDATED ACTUAL
EXAM QUESTIONS AND CORRECT
ANSWERS FULL SOLUTION GRADED A+
◉ What separates the crust and the mantle? Answer: *Moho*
◉ What 2 layers does the upper mantle consist of? Answer:
*Lithosphere* (semi-core)
Varies in thickness
Boundary with asthenosphere difficult to define (melts and becomes
incorporated in asthenosphere)
*Asthenosphere* extends 100-300km
Semi-molten/viscous - Allows rock to move due to high pressure in
mantle.
Flowing slowly
◉ What are continental and oceanic plates made up of? Answer:
Lithosphere and crust
◉ Where do convection currents exist?
What do these do? Answer: Asthenosphere
,Caused by vast amounts of heat generated in mantle.
Semi-molten asthenosphere flows carrying with it the solid
lithosphere and crust.
◉ What are the properties of the *continental crust*? Answer:
Thickness:
35km average (<30-70km)
Density:
2.6-2.7
Mineral composition:
Mainly granitic, silicon, aluminium
◉ What are the properties of the *oceanic crust*? Answer: Thickness:
5-10km
Density:
3.0
Mineral composition:
Mainly basaltic, silicon and magnesium
◉ What are the properties of the *mantle*? Answer: Thickness:
,To a depth of 2900km
Density:
3.3 at Moho
5.6 at core
Mineral composition:
Rich in magnesium and iron
◉ Explain the movement of the crust caused by convection currents
in the mantle. Answer: Hot rock rises from lower to upper
asthenosphere.
Hot rock spreads and cools, pushing plates apart.
Cool rock sinks back down towards core.
As (oceanic) plate subducts at ocean trenches, gravity pulls it under
(*slab pull*).
Rising mantle pushes crust upwards at mid-ocean trenches, while
gravity pulls it back down (*ridge push*).
, ◉ What was Alfred Wegener's big idea? Answer: 250 million years
(Carboniferous period), all the Earth's continents fit together
(*Pangea*).
Over time, continents have moved apart through *continental drift*.
◉ Explain 3 pieces of (Wegener's) *geological* (rocks) evidence for
continental drift. Answer: *Mountain chains and rock sequences on
opposite sides of oceans show close similarities* (e.g. northeast
Canada and northern Scotland).
- These mountains are likely to have been created together and then
split apart as the continents moved.
*Continents seem to fit together* (particularly South America and
Africa).
- Suggests that continents once fit all together and continental drift
has separated them.
- (Erosion wouldn't've made them this shape).
*Evidence of glaciations 290 million years ago in southern Africa,
Australia, South America, India and Antarctica*.
- Suggests these land masses were joined during this time, located
close to the South Pole.
- (India has a tropical climate now, and due to it's current location it
wouldn't have been glaciated in an ice age.
- Suggests India was one at a higher latitude further from the equator).
EXAM QUESTIONS AND CORRECT
ANSWERS FULL SOLUTION GRADED A+
◉ What separates the crust and the mantle? Answer: *Moho*
◉ What 2 layers does the upper mantle consist of? Answer:
*Lithosphere* (semi-core)
Varies in thickness
Boundary with asthenosphere difficult to define (melts and becomes
incorporated in asthenosphere)
*Asthenosphere* extends 100-300km
Semi-molten/viscous - Allows rock to move due to high pressure in
mantle.
Flowing slowly
◉ What are continental and oceanic plates made up of? Answer:
Lithosphere and crust
◉ Where do convection currents exist?
What do these do? Answer: Asthenosphere
,Caused by vast amounts of heat generated in mantle.
Semi-molten asthenosphere flows carrying with it the solid
lithosphere and crust.
◉ What are the properties of the *continental crust*? Answer:
Thickness:
35km average (<30-70km)
Density:
2.6-2.7
Mineral composition:
Mainly granitic, silicon, aluminium
◉ What are the properties of the *oceanic crust*? Answer: Thickness:
5-10km
Density:
3.0
Mineral composition:
Mainly basaltic, silicon and magnesium
◉ What are the properties of the *mantle*? Answer: Thickness:
,To a depth of 2900km
Density:
3.3 at Moho
5.6 at core
Mineral composition:
Rich in magnesium and iron
◉ Explain the movement of the crust caused by convection currents
in the mantle. Answer: Hot rock rises from lower to upper
asthenosphere.
Hot rock spreads and cools, pushing plates apart.
Cool rock sinks back down towards core.
As (oceanic) plate subducts at ocean trenches, gravity pulls it under
(*slab pull*).
Rising mantle pushes crust upwards at mid-ocean trenches, while
gravity pulls it back down (*ridge push*).
, ◉ What was Alfred Wegener's big idea? Answer: 250 million years
(Carboniferous period), all the Earth's continents fit together
(*Pangea*).
Over time, continents have moved apart through *continental drift*.
◉ Explain 3 pieces of (Wegener's) *geological* (rocks) evidence for
continental drift. Answer: *Mountain chains and rock sequences on
opposite sides of oceans show close similarities* (e.g. northeast
Canada and northern Scotland).
- These mountains are likely to have been created together and then
split apart as the continents moved.
*Continents seem to fit together* (particularly South America and
Africa).
- Suggests that continents once fit all together and continental drift
has separated them.
- (Erosion wouldn't've made them this shape).
*Evidence of glaciations 290 million years ago in southern Africa,
Australia, South America, India and Antarctica*.
- Suggests these land masses were joined during this time, located
close to the South Pole.
- (India has a tropical climate now, and due to it's current location it
wouldn't have been glaciated in an ice age.
- Suggests India was one at a higher latitude further from the equator).
