Tectonic Topic 1

Question 1

State the range of characteristic of the [core, mantle, crust]

Answer 1

1. innermost > in between > outermost
2. Highest > 1000-3700> lowest
3. Thickest> 2900 km > thinnest

Question 2

How do convection currents lead to tectonic plate movement

Answer 2

1. Heat from the earth’s core causes the mantle to be less dense
2. the less dense mantle material will rise towards the surface
3. The rising convection currents spread beneath the plates and drag them apart
4. The mantle will then loss heat and sink towards the core as it become denser
5. The material then gets heated up again and repeats the process

Question 3

How does slab-pull force contribute to tectonic plate movement

Answer 3

1. When two plates converge, the denser oceanic crust is pulled down by gravity as it subducts
2. The denser oceanic crust sinks deeper into the mantle under its own weight

Question 4

What is the evidence of seafloor spreading?

Answer 4

1. Where two plates move away from each other at divergent plate boundaries, seafloor spreading occurs
2. Magma from deep within the earth rises through the mid-ocean ridge
3. New oceanic crust is formed

Question 5

Why does seafloor spread support the plate tectonic theory?

Answer 5

1. The rocks nearer to the crest of the mid-ocean ridge are the youngest
2. Rocks further away from the ridge are progressively older
3. New oceanic crust is created at divergent boundaries, then moves laterally on both sides of the mid-ocean ridge
4. Older oceanic crust is being destroyed at oceanic trenches
5. New crest is continually formed at divergent boundaries while older crest is being destroyed at the oceanic trenches

Question 6

Explain what magnetic striping is

Answer 6

1. Geographic north and south does not change
2. Magnetic north and south can shift
3. When the geographic north point towards magnetic north it is known as normal polarity
4. Reverse polarity is when the geographic north point towards the magnetic south

Question 7

Describe the Magnetic striping

Answer 7

• Magnetic striping is the zebra-like pattern where there are strips of normal polarity rocks alternating alongside strips of reversed polarity
• It is symmetrical on both sides of the mid-ocean ridge

Question 8

Why does the magnetic striping occur?

Answer 8

1. Basaltic rocks from the oceanic crust are volcanic rocks formed from iron-rich lava
2. They contain magnetic materials
3. When iron-rich lava erupts, it cools and solidifies
4. Magnetic material points towards Earth’s north

Question 9

Why does magnetic striping support plate tectonic theory?

Answer 9

1. The zebra-like pattern is symmetrical on either side of mid-oceanic ridge
2. Oceanic plates move away from each other
3. Iron-rich lava erupts from the centre of the ridge
4. Lava cools, solidifies and form new oceanic crust
5. The crust is then pushed in both directions away from the ridge

Question 10

Oceanic-oceanic divergent plate

Answer 10

1. The two oceanic plates will move away from each other.
2. The decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma
3. Magma rises through weak areas in the crust and fills gaps caused by the spreading plates
4. Lava cools and solidifies to form basaltic rocks
5. The rocks make up a new oceanic crust

Question 11

How does the Oceanic-Oceanic divergent plate create mid-ocean ridges, volcanoes, and earthquakes

Answer 11

1. An extensive underwater mountain chain (mid-ocean ridge) forms because of the basaltic rocks making up a new oceanic crust
2. At the centre of the deep ridge valley, magma rises through weak areas in the crust to form submarine volcanoes. After many eruptions, the volcanoes may break the surface of ocean to form volcanic island
3. Earthquakes occur here due to the stress and tension released when plates moved

Question 12

Continental-continental divergent plate boundaries

Answer 12

1. Two continental plates move apart
2. Rocks eventually fracture to form parallel faults
3. The rock between these faults collapses to form a deep rift valley with steep sides
4. As the plate moves apart, the decrease in overlying pressure causes parts of the underlying mantle to melt forming magma.
5. Magma rises through weak areas in the crust, forming volcanoes.
6. Earthquakes occur as stress and tension are released when plates move

Question 13

Oceanic-oceanic convergent plate boundaries

Answer 13

1. Two oceanic plates collide
2. The denser plate subducts beneath the less dense plate
3. This forms a deep depression known as oceanic trench
4. As the subducting plate sinks into the mantle, the high-pressure forces water out. Water lowers the melting point, forming magma
5. Magma rises through weak areas
6. This forms a chain of volcanoes known as Volcanic plates
7. Friction along the subducting oceanic plate also causes earthquake

Question 14

Continental-continental convergent plate boundaries

Answer 14

1. Two continental plates collide
2. Subduction does not take plate, as the continental plates are too buoyant to subduct
3. Huge pressure causes the rocks to be uplifted and buckled to form fold mountains
4. Friction along the plate boundary causes earthquakes

Question 15

Oceanic-continental convergent plate boundary

Answer 15

1. Oceanic plate collides with continental plate
2. The denser oceanic plate subducts beneath the less dense continental plate
3. This forms an oceanic trench
4. The subducting plate sinks into the mantle, the high-pressure forces water out, lowers the melting point and forming magma
5. Magma rises through weak areas, forming volcanoes on the continental plate
6. Huge pressure at this plate boundary causes rocks on the continental plate to be uplifted and buckled, forming fold mountains

Question 16

Transform plate boundary

Answer 16

1. Tectonic plates slide past each other
2. No crust is destroyed or created
3. Stress caused by the plate movement produces a fault
4. Earthquakes occur as one plate suddenly slips past another