Chapter 3

Question 1

What is plate tectonics?

Answer 1

The theory that states that Earth’s crust is sepperated into plates or pieces that move.

Question 2

What are plate boundaries and why are they so important? Give examples of all three types.

Answer 2

Divergent - Mid Atlantic Ridge
Convergent - South Coast of British Columbia
Transform- San Andres Fault System
Passive- East Coast North America

Question 3

What is an earthquake?

Answer 3

A shaking of the ground caused by a release of energy inside the Earth.

Question 4

Where do most earthquakes occur?

Answer 4

Most take place at the plate margins. Most occur at convergent and transform plate margins.

Question 5

What are period, frequency, wavelength and amplitude?

Answer 5

Period - The time it takes a wave to travel one wavelength.
Frequency - The distance a wave travels in a given time.
Wavelength - The distance between crests.
Amplitude -

Question 6

What is a P wave?

Answer 6

Primary waves - Faster speed about 8km/second.

These waves cause objects to move back and forth horizontally depending on which direction the waves come from.

Question 7

What is an S wave?

Answer 7

Secondary waves - slower speed about 5km/second

These waves cause objects to move up and down.

Question 8

What is a body wave?

Answer 8

An energy wave that travels through the Earth.

Question 9

What is a surface wave?

Answer 9

An energy wave that travels along the surface of the earth.

Question 10

How do velocities of P and S waves differ from one another?

Answer 10

Primary wave = 8km/s

Secondary wave = 5km/s

Question 11

What is a seismograph?

Answer 11

A sensitive instrument used to measure ground motion.

Question 12

How does a seismograph work?

Answer 12

1. A frame that is fixed to the Earth. This part will move with the ground.
2. A heavy weight connected to the frame. This part will not move with the ground.
3. On the weight is a pen that will not move in an earthquake. On the frame is a writing surface that will move.

Question 13

What is a fault?

Answer 13

A break in the Earth’s crust along which there is movement.

Question 14

What is a normal fault and what causes it?

Answer 14

Caused by tensional stress

Question 15

What is a reverse fault and what causes it?

Answer 15

Caused by compressive stress

Question 16

what is a strike-slip fault and what causes it?

Answer 16

Right and Left lateral strike strip is caused by sheer stress.

Question 17

What is the difference between stress and strain?

Answer 17

Stress is the unequal application of force where Strain is how an object responds to stress. Under stress a rock body will either bend or break.

Question 18

What factors affect stress and strain in a rock body?

Answer 18

1. Composition: The number and type of different minerals.
2. Texture: The size, shape and packing of crystal grains.
3. Structure: The presence of faults, fractures or bedding planes.

Bedding planes separate 1 bed or 1 layer from another.

Question 19

What is the elastic rebound theory?

Answer 19

When a rock bends when subjected to a force and then returns to its original shape when the force is removed. ex: Vancouver Island.

Question 20

What is the Mercalli Intensity Scale?

Answer 20

Intensity Scale - Measures information about the magnitude as well of the damage done.

Question 21

What are the limitations of the Mercalli Intensity Scale?

Answer 21

Limitations to this scale - It may rely only on local features that are not always found everywhere. ex: Not all houses are built the same.

Question 22

What is the magnitude scale?

Answer 22

Richter Scale - Based on earthquakes wave amplitude, 0-9, Every interval increases in magnitude by 10x.

Question 23

What is an Earthquake Environmental Effect Scale? (EEE)

Answer 23

Indicates the effects an earthquake may have on the natural environment. In particular, the changes observed along the faults.

Question 24

How does liquefaction occur?

Answer 24

Due to Porosity - the space inside a rock or sediment deposit, and Permeability - A measure of how well connected individual pores are.
This creates a less stable deposit that is able to flow or move like a fluid.
Ground motion during an earthquake can force water in the ground to move. This creates places of higher and lower pressure underground.
Where pressure is high, sediment grains are forced apart and the ground begins to flow.

Question 25

What is quick clay?

Answer 25

A clay mineral is a silicate mineral that has a very high surface area to volume ration. It is made up of sheets similar to a sheet of paper. The large surface areas of clay minerals are also electrically charged, This allows clay minerals to store electricity charged atoms or molecules at their surface.

Question 26

How does bedrock composition, structure and temperature affect earthquake energy?

Answer 26

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Question 27

Explain the events of Jan 9, 1965 near Hope, BC

Answer 27

A large landslide took place in the coast mountains. A large mass of rock fell from Johnson Peak. The exposed igneous and metamorphic rock was weathered, unstable and sitting at a steep incline.
Wet, water saturated conditions at the time and an earthquake in the area triggered this event.