Lecture 4 - Volcanic Imagination

Question 0

A Quake struck the region of Yerevan and Tbilisi on what date, and what was magnitude and how many killed, injured?

Answer 0

23 October 2011
7.2M
600 dead, 4000 injured

Question 1

What are the tectonic plates by the region of Yerevan and Tbilisi?

Answer 1

Arabian and Eurasian plates

Question 2

What does an earthquake release energy in the form of?

Answer 2

Wave

Question 3

How may a wave be reflected, deflected or retracted?

Answer 3

If the strength or density of the Earths interior changes

Question 4

What can be used to probe and understand the Earths interior?

Answer 4

Earthquake waves

Question 5

What happens to seismic waves when density of rock changes?

Answer 5

They bend and change speed

Question 6

What are p waves?

Answer 6

Primary waves

Question 7

Name 3 components of p waves?

Answer 7

1. They travel through solids, liquids or gaseous materials
2. They are the fastest of the 3 seismic waves
3. Also called, push-pull waves

Question 8

What are S waves also called?

Answer 8

Secondary waves

Question 9

Name 3 components of S waves?

Answer 9

1. Travel at half the velocity of P waves
2. They have shear waves, and push material at right angles to their direction of travel
3. Shear waves are only present in solids

Question 10

Name 2 components of surface waves?

Answer 10

Travel around NOT through the Earths surface

Velocity slightly less than S Waves

Question 11

What does the push pull, P Wave (compressional wave) do to material travelling in same direction?

Answer 11

Compresses and expands the material

Question 12

What do S Waves shake?

Answer 12

The ground up and down, back and forth at right angles to the direction of travel

Question 13

Surface waves (Rayleigh and Love waves) are like what?

Answer 13

Waves in the ocean

Question 14

What increases with P and S waves?

Answer 14

Intervals, the further you get from te epicentre

Question 15

Describe compressional waves, by Larry Braile, Purdue Universities animation (2010)

Answer 15

Particle motion has changing compression and dilation. Particle motion is parallel to direction of propagation. Material returns to original shape

Question 16

Describe Shear Waves (S Waves) using animation by Larry Braile, Purdue Universities animation (2010)

Answer 16

Particle motion consists of alternating transverse motion. Particle motion perpendicular to direction of travel. Material returns to original shape

Question 17

Describe Rayleigh waves (R-Waves) using animation by Larry Braile, Purdue Universities animation (2010)

Answer 17

Particle motion has elliptical motions in vertical plane and is parallel to direction of propagation. Amplitude decreases with depth. Material returns to original shape

Question 18

Describe love waves (L-Waves) using animation by Larry Braile, Purdue Universities animation (2010)

Answer 18

Particle motion consists of alternating transverse motions. Particle motion horizontal and perpendicular to direction of propagation. Amplitude decreases with depth. Material returns to original shape

Question 19

What is 2 components is the crust made of?

Answer 19

Oceanic Basalt

Continental Andesite

Question 20

What can be found in the upper mantle? Think about the ‘Big Hole’ at Kimberly, South Africa.

Answer 20

Diamonds, they are formed in the upper mantle, bought to surface by volcanic rock called Kimberlite

Question 21

What is Peridotite?

Answer 21

Special for of basalt that occurs in the Earths mantle

Question 22

What can be found in the Lower mantle, name 2 things?

Answer 22

• Perivskite - magnesium silicate mineral

- Iron-Nickel meteorites

Question 23

What did Anderson Celsius notice in Southern Sweden in the 18thC?

Answer 23

It was rising by 3cm a year

Question 24

What happens with the weight of ice during glacial periods?

Answer 24

It pushes down the earths surface and lithosphere

Question 25

What happens during a glacial period when the ice sheet melts?

Answer 25

The displaced mantle flows back and the depression rises

Question 26

When the displaced mantle flows back and depression rises after a glacial period, what does the mantle appear to do?

Answer 26

Bulge and ‘flow’

Question 27

What is the temperature gradient at Gold Reef City Mine - Jo’Burg?

Answer 27

12.5degrees km-1

Question 28

Why is the temperature gradient not constant?

Answer 28

Rocks of mantle are mixed by convection currents, so heat is distributed more evenly

Question 29

Can the mantle convect?

Answer 29

Depends on it’s Rayleigh number

Question 30

What is runniness or viscosity measure in? Also give 3 examples?

Answer 30

Poise - the higher a value = the more sticky

E.g - Water - 0.0114

• Maple Syrup - 320000
• Mantle 10000000000000000000000 (22noughts)

Question 31

What happens if rock is heated and put under enough pressure?

Answer 31

It will flow

Question 32

Conclusion: the movement of Earthquake waves (refraction and reflection) through the earths interior suggests what?

Answer 32

The earths interior is like a scotch egg.

Crust, mantle, outer core, inner core

Question 33

Conclusion: how can composition of layers of rock be deduced?

Answer 33

By examining terrestrial and extra terrestrial rocks

Question 34

Conclusion: the 3-D structure of heat flow in Earths mantle suggest presence of convection currents, what does this mean?

Answer 34

It is the most probable force for plate movement