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1
Q

Are Oceanic or Continental Plates denser and what does this mean for tectonics

A

Oceanic crust is denser - the denser plate is always the one that subducts

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2
Q

What is a Convergent Plate Boundary

A

When two plates collide with each other

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3
Q

What happens at a Convergent Plate Boundary for the following:

Oceanic-Oceanic

Oceanic-Continental

Continental-Continental

A
  • Oceanic-Oceanic: The older and colder one (more dense) subducts below the other
  • Oceanic-Continental: The Oceanic crust subducts as it is denser
  • Continental-Continental: The two plates collide but as neither can subduct they push each other upwards
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4
Q

Give two examples of a Convergent Plate Boundary

A
  • Between the Nazca and South American Plate, where the Oceanic Nazca plate has subducted under the South American plate creating the Andes Mountains
  • The Himalayas where the continental Indian Plate and Eurasion Plate collided and pushed each other upwards forming the Himalayas
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5
Q

What is the term for a place where subduction occurs

A

Subduction Zones

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6
Q

What is subduction

A

When one plate (denser than the other) slides beneath the other, getting melted by the mantle into magma

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7
Q

What is Slab Pull

A

The process of the part of the crust that is mid-subduction pulling the rest of the crust with it

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8
Q

What is the name for a place where collisions occur at a continental-continental covergent boundary

A

Collision Margin

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9
Q

How are mountains formed as a result of subduction

A

As one crust slides beneath the other crust, the less dense crust is forced upwards by the denser subducted crust forming mountains

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10
Q

How are volcanoes formed as a result of subduction

A

When the denser crust enters the mantle, it is melted into magma, which is less dense than the crust above. This causes it to rise up creating volcanoes on the surface

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11
Q

How are deep sea trenches formed at Oceanic-Oceanic Convergent Plate Boundaries

A

They are the gap between the lowered subducted plate and the raised other plate

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12
Q

What are the two types of volcano are what is a word to describe each of them

A

Shield Volcanoes - Effusive
Composite Volcanoes - Explosive

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13
Q

What is the difference between effusive and explosive eruptions

A
  • Effusive eruptions have less pressure so its eruptions are mostly lava flowing out the top
  • Explosive eruptions have higher pressure so when the eruption begins the lava, rocks and gas would go flying really high in the air
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14
Q

What type of volcanoes form at convergent plate boundaries

A

Composite

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15
Q

What is a divergent plate boundary

A

When two plates move away from each other and pull apart

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16
Q

What % of earthquakes are found at convergent plate boundaries

A

80%

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17
Q

What happens at divergent plate boundaries

A

The two plates pull away from each other

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18
Q

How do divergent plate boundaries create new land

A

When the plates move apart, there is a gap which allows the mantle to release its pressure. This causes part of the mantle to melt into magma, which rises through the gap between the two plates to produce new crust OR form a volcano

19
Q

What is seafloor spreading

A

The creation of new crust at the divergent plate boundary which pushes the crust either side of the boundary in different directions

20
Q

What is ridge push

A

The process of the seafloor moving horizontally away from the divergent plate boundary as a result of seafloor spreading.

21
Q

What is an ocean ridge

A

An elevated part of land on the divergent plate boundary which is where the crust is formed and seafloor spreading occurs. It is often in the form of mountains

22
Q

What is a rift valley

A

A flat stretch of land between two divergent plate boundaries which has been made horizontal by seafloor spreading

23
Q

What type of volcanoes form at divergent plate boundaries

A

Shield volcanoes

24
Q

Do earthquakes occur at divergent plate boundaries and how strong are they

A

Yes but are quite weak

25
Q

Give an example of divergent plate boundaries

A

Mid atlantic ridge (in Atlantic Ocean and Iceland)

26
Q

What are conservative plate boundaries also known as

A

Transform plate boundaries

27
Q

What happens at conservative plate boundaries

A

Two plates do not move closer or further but slide past each other, either in different directions or at different speeds

28
Q

What are the 3 main types of tectonic hazards

A

Earthquakes, Volcanoes, Tsunamis

29
Q

What are ‘intra-plate’ hazards

A

Hazards that occur in the middle of a plate, far from a plate boundary

30
Q

Name 3 possible reasons for intra-plate earthquakes

A

-Movements and friction upon old fault lines created by previous plate movements
- isostatic readjustment
- human activities

31
Q

What is isostatic readjustment

A

Weight of ice removed after the Ice Age can cause the ground to move up or down after losing all the extra weight, causing earthquakes

32
Q

Give 3 examples of human activities that can cause earthquakes

A
  • Storing water in reservoirs being to heavy
  • Fracking of gas
  • Large explosions
33
Q

How are intra-plate volcanoes formed? Are they more common in oceanic or continental plates and why?

A

If the crust is thin enough, magma from mantle plumes will be able to melt through the ground and onto the surface, creating a volcano. They occur more in oceanic plates as the crust is thinner on average

34
Q

How thick is oceanic and continental crust

A

Oceanic: 6-7km thick
Continental: 35-40km thick

35
Q

Name a place that experiences intra-plate earthquakes and how many are felt per year

A

The UK - 25 felt a year (although weak)

36
Q

Name a place that has intra-plate volcanoes and how many

A

Hawaii - has 15

37
Q

What is a mantle plume

A

A place where molten viscous silicate material from the mantle rises closer to the surface than normal (700km below the lithosphere/crust)

38
Q

What do mantle plumes form

A

‘hot spots’, where magma rises through the asthenosphere and sometimes through the crust, creating volcanoes

39
Q

Where are the two massive mantle plumes on Earth

A
  • under the Pacific Plate
  • under the African Plate
40
Q

What is the lithosphere

A

The solid outer layer of the Earth made of the crust and upper mantle

41
Q

What is plate tectonic theory

A

The theory that the Earth’s lithosphere is made up of a number of tectonic plates

42
Q

What are the four main evidences for Plate tectonic theory

A
  • Charactertistics of the Earth’s Structure
  • Mantle Convection
  • Paleomagnetism and Sea Floor Spreading
  • Subduction and Slab Pull
43
Q

How does the structure of the Earth act as evidence for plate tectonic theory

A
44
Q
A

Physical Geography Tectonic Processes and Hazards (1 decks)

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