tectonics kq2 - landforms

Question 1

what forms at c-c divergence

Answer 1

Rift valleys and block mountains
(overtime) Tensional forces pull sections of crust apart = central section of crust subsides (sinks) = forms range of lowland = rift valleys

Rift valleys: linear depression that lies between higher land - has sttep slopes and flat valley floor (where water bodies may form)

Sections next to rift valley become range of highlands = block mountains (highlands over 600m in height - have flat tops and steep slopes)

Volcanoes
Tensional forces pull plates and crusts apart = crusts weaken = form faults
difference in pressure = magma from the mantle rises through the faults = erupts as lava onto the surface
lava cools and hardens around the fault with ash from the eruption = forms first layer of volcano
Overtime, more eruptions = more layers of ash and hardened lava formed = creates a mountain that erupts lava = volcano

Question 2

O-O divergence

Answer 2

Mid oceanic ridge: long line of highlands that run parallel to plate boundary and fault lines
- Tensional forces pull plates apart = create gap between plates
- difference in pressure = magma from the mantle rises to the surface = accumulate at the edge of the oceanic plates
- magma cools and hardens to become the new ocean floor
- the pressure from the rising magma pushes and raises the edge rof the oceanic crust
- Overtime, more magma accumulates together with the raised edges = a range of raised ocean floor is formed at the edge of the oceanic plate = mid-oceanic ridge.

Underwater volcanoes
Tensional forces pull the plates apart = weakens the crust = forms faults
difference in pressure = magma from the mantle rises through the faults = erupts as lava onto the surface.
lava cools and hardens around the fault = forms the first layer of the volcano.
Overtime = more eruptions = more layers of hardened lava are formed = creates a mountain that erupts lava = a volcano.
Some of these volcanoes may be tall enough to emerge above the sea level, = volcanic islands

(gap and faults are different)

Question 3

why is O-O divergence known as constructive plate boundary

Answer 3

O-O divergence is known as constructive plate boundary: oceanic crust expands in size as new ocean floor spreads outwards
Crust nearer to ridge is ‘younger’ - newly escaped and hardened magma
Crust further from ridge is ‘older’ - earlier formed crust that was carried away by gradual plate movement

Question 4

C-C convergence

Answer 4

fold mountains
collision of plates led to compressional forces acting on the crust
Continental plates made up of soft sedimentary rocks = forces cause layers of rocks in the continental crust to weaken and then buckle and fold = synclines (form valleys)
parts of the layers of rocks also get uplifted and create multiple peaks = anticlines (form mountain peaks)
Overtime, the layer of rocks folds and gets uplifted further = creates a range of highlands (series of anticlines and synclines) = fold mountains

Question 5

O-O convergence

Answer 5

Collision of plates led to compressional forces acting on the crust
Oceanic trench:
Mantle material from convectional current sinks = edge of denser oceanic crust sinks
Edge of denser oceanic crust subducts below less dense oceanic crust = point where this occurs is called subduction zone
Overtime = a underwater range of narrow depression is formed at the
subduction zone = oceanic trench

Underwater volcano - form on less dense oceanic plate
Compressional force weakens the crust = faults formed
Subducted crust melts in mantle = forms magma = rises to crust
Difference in pressure = magma from the mantle rises through the faults = erupts as lava onto the surface
Lava cools and hardens around the fault = forms the first layer of the volcano.
Overtime = more eruptions = more layers of hardened lava formed = creates a mountain that erupts lava = volcano.
Some of these volcanoes may be tall enough to emerge above the sea level = form volcanic islands

Question 6

O-C convergence (with subduction)

Answer 6

1. fold mountains
   collision of plates led to compressional forces acting on the crust
   Continental plates made up of soft sedimentary rocks = forces cause layers of rocks in the continental crust to weaken and then buckle and fold = synclines (form valleys)
   parts of the layers of rocks also get uplifted and create multiple peaks = anticlines (form mountain peaks)
   Overtime, the layer of rocks folds and gets uplifted further = creates a range of highlands (series of anticlines and synclines) = fold mountains on continental crust

Collision of plates led to compressional forces acting on the crust
2. Oceanic trench:
Mantle material from convectional current sinks = edge of denser oceanic crust sinks
Edge of denser oceanic crust subducts below less dense continental crust = point where this occurs is called subduction zone
Overtime = a underwater range of narrow depression is formed at the
subduction zone = oceanic trench

3. Volcano - form on less dense continental plate
   Compressional force weakens the crust = faults formed
   Subducted crust melts in mantle = forms magma = rises to crust
   Difference in pressure = magma from the mantle rises through the faults = erupts as lava onto the surface
   Lava cools and hardens around the fault = forms the first layer of the volcano.
   Overtime = more eruptions = more layers of hardened lava formed = creates a mountain that erupts lava = volcano.
   Some of these volcanoes may be tall enough to emerge above the sea level = form volcanic islands