tectonics chpt 1

Question 1

How do convection currents lead to tectonic plate movement

Answer 1

1. heat from earth’s core causes mantle material to be less dense
2. mantle material rises towards surface
3. rising convection current spread beneath plates and drags them apart, causing divergent plate movement
4. mantle loses heat and sinks back towards core
5. convergent plate movements occur when convection currents collide
6. mantle heated up again, process repeats - rising and sinking of mantle forms convection currents

Question 2

What is the slab pull force?

Answer 2

1. when 2 plates converge, the denser oceanic plate will subduct beneath the less dense oceanic plate due to gravity
2. denser oceanic crust sinks deeper into mantle bc of its own heavy weight and pulls the rest of the plate with it - further convergence

Question 3

Evidence of seafloor spreading?

Answer 3

1. seafloor spreading occurs when two plates move apart from each other at divergent plate boundaries
2. magma from deep within earth rises through mid ocean ridge
3. forms new oceanic crust

rocks nearest to centre of ridge are youngest, rocks further away are oldest
proves that new oceanic crust is created at divergent plate boundaries and moves laterally along ridge as seafloor spreading continues

Question 4

What is magnetic striping?

Answer 4

1. magnetic north at geo south - reverse polarity
2. magnetic north at geo north - normal polarity
3. normal and reverse polarity has flipped multiple times over time
4. magnetic striping is the zebra like pattern of the normal polarity rocks alternating with the reverse polarity rocks on the seafloor
5. symmetrical on both sides of mid ocean ridge

Question 5

How magnetic striping occur and how does it prove the plate tectonics theory?

Answer 5

1. oceanic plates move away from each other
2. iron rich lave erupts from centre of ridge
3. cools and solidifies, forming new oceanic crust
4. crust is pushed away at both directions of the ridge when new lava erupts due to movement of oceanic plates
5. cools and solidifies, forming basaltic rocks
6. rocks point towards earth’s magnetic north at the time
7. records the alternating polarities
8. over time, more and more oceanic divergent plate boundaries, lead to more and more lava, forms symmetrical zebra like pattern

Question 6

What happens at oceanic-oceanic divergent plate boundaries?

Answer 6

1. oceanic plates move apart
2. forms mid ocean ridge
3. decrease in overlying pressure allows water from oceanic crust to flow into mantle, reducing melting point
4. mantle melts into magma, rises to surface , fills gaps caused by plates
5. lava cools and solidifies, forming basaltic rocks
6. forms new oceanic crust, contributes to mid ocean ridge

Question 7

What happens at continental continental divergence?

Answer 7

1. continental plates move apart
2. rocks fracture to form parallel faults
3. rocks btwn faults collapse to form deep rift valley with steep sides
4. decrease in overlying pressure causes parts of underlying mantle to melt and rise to surface, lava
5. EQ formed due stress and tension released when rocks collapse

Question 8

What happens at oceanic oceanic convergence?

Answer 8

1. 2 oceanic plates collide
2. denser oceanic plate subducts beneath less dense plate
3. forms a deep depression called the oceanic trench
4. subducting plate sinks, high pressure forces water out of oceanic plate, reduces mp of mantle, mantle melts into magma, rises to surface
5. forms a chain of volcanoes, known as a volcanic island
6. friction btwn plates causes EQ

Question 9

What happens at continental continental convergence ?

Answer 9

1. 2 continental plates collide
2. no subduction, continental plates too buoyant to subduct
3. enormous pressure causes rocks to buckle and be uplifted to form fold mountains
4. friction causes EQ
5. no magma

Question 10

What happens at oceanic continental convergence?

Answer 10

1. oceanic and continental plate collide
2. oceanic plate subducts, forms deep depression called oceanic trench in subduction zone
3. high pressure forces water out of oceanic crust, lowers mp of mantle, melts to form magma, rises to surface, forming volcanoes on continental plate
4. friction causes EQ
5. enormous pressure causes rocks in continental plate to be uplifted and buckled, forming fold mountains

Question 11

what happens at transform plate boundaries ?

Answer 11

1. 2 plates slide past each other
2. stress caused by plate movement forms faults - a zone of fractures
3. no EQ
4. no magma