Plate Tectonics Flashcards

1
Q

What are plate tectonics?

A

Framework for understanding the Earth’s large scale behaviour.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are some ideas about plate tectonics?

A
  • Earth lithosphere divided into nearly rigid plates
  • Oceanic crust can be part of continental crust, but is much denser, so more easily created or destroyed
  • Surface area constant: sea floor spreading balanced by consumption of plate material elsewhere
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are 6 pieces of evidence for plate tectonics?

A
  • Jigsaw fit
  • Geological evidence (similar rock types across continents
  • Palaeontology (similar species)
  • Palaeomagnetism (record of magnetic field reversals)
  • Seismic activity (earthquake activity shows pattern of stress in crust)
  • Volcanism (hot spots indicate mantle plumes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 3 types of plate boundary?

A
  • Constructive
  • Destructive
  • Conservative
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe a constructive plate boundary.

A
  • Plates moving away from eachother (parallel or at angle)
  • Creates new lithosphere, usually at mid-ocean ridges
  • Magma upwells and cools, creating basaltic crust
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two types of spreading for constructive plate boundaries and what is the equation for their relative velocities?

A

Normal spreading is parallel, whereas oblique spreading is at an angle.

v0 = |B V(A)| = |A V(B)|

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe a destructive plates boundary.

A
  • Volcanoes and earthquakes occur
  • One plate being subducted under another
  • Plate material forced into mantle
  • Usually dense oceanic crust under less dense continental crust
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe a conservative plate boundary.

A
  • Plates slide past each other
  • No lithosphere created or destroyed
  • Many small earthquakes to release stress build up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What do real plate boundaries normally look like?

A

Segments of constructive boundaries connected to segments of conservative boundaries, as boundaries are not straight lines.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are plates described as? What can we approximate?

A

Plates are ‘spherical cap segments’. We can approximate a flat earth ~100km.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a triple function?

A

Where three plate boundaries meet. many different types depending on the 3 types of boundary.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What can we do to calculate the unknown velocity of one of the plate boundaries?

A

Can use vector addition.

c) VB = (c) VA + (a) VB (use pythagoras to determine third velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can we say plate motion is similar to?

A

A rotation of the plate about an axis passing through the centre of Earth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do we need to fully describe the relative motion between 2 plates?

A

The latitude and longitude of one pole of the rotation axis, plus it’s rotation vector.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the notation for each pole on the rotation axis?

A

P = positive rotation pole = clockwise, N = negative pole = anticlockwise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the equation for the velocity of a specific point?

A

v = ωR(earth)sin(Δ), where Δ is the angular distance from the pole to the point (centred at earths centre) and ω is the angular velocity of the rotation pole.

17
Q

What is the standard convention for describing plate velocities?

A

Half the velocity as is 2 plates moving relatively, so each plate has v/2

18
Q

How do we find the position of the rotation pole?

A

Found by constructing perpendicular lines from conservative boundaries.

19
Q

What are 3 other ways to measure plate velocities?

A
  • Displacement survey (how much a river moves after earthquake)
  • GPS (measure change in relative position of GPS ground stations)
  • Very long baseline interferometry (measure separation of radio telescopes using astronomical objects)