Easc 104 Midterm 2 Study Guide

Front 1

What is mass wasting?

Back 1

Any type of downslope movement of rock or sediment because of gravity

Front 2

What is the driving force in mass wasting?

Back 2

Gravity

Front 3

What are the 3 main factors that cause mass wasting events?

Back 3

1. Nature of slope
2. Amount of water
3. Steepness and instability of slopes

Front 4

How does the nature of slope influence the likelihood of mass wasting events?

Back 4

- Slopes made up of unconsolidated (loose) sediments are more likely to fail
- Angle of repose: the angle at which unconsolidated material becomes unstable; varies with material cohesion

Front 5

What is the relationship between consolidated material and mass wasting?

Back 5

The more cohesive and adhesive the material (i.e. more consolidated), the less likely mass wasting is

Front 6

How does increased water content influence the likelihood of slope failure?

Back 6

1. Water increases the weight of the slope and decreases the strength of the material in the slope (i.e. material becomes less cohesive), thereby increasing the likelihood of slope failure
2. Pore pressure in the slope increases, and clay materials become hydrated and expand

Front 7

When do slopes fail?

Back 7

When gravitational forces exceed the strength of rock or soil which comprise the slope

Front 8

What are driving forces in mass wasting events?

Back 8

Forces that move materials downslope (e.g .weight of slope material due to things placed on the slope such as vegetation, fill material, or buildings)

Front 9

What are resisting forces in mass wasting events?

Back 9

Forces that oppose downslope movement (i.e. shear strength of the material)

Front 10

What is a factor of safety?

Back 10

The ratio of resisting forces to driving forces.
When greater than 1, slope is stable
When less than 1, slope is unstable

Front 11

What are the 3 types of mass movements?

Back 11

1. Fall
2. Slide
3. Flow

Front 12

What are the characteristics of falls?

Back 12

- Consolidated material (rock)
- Fast (5km/hr+)
- Rocks fall through the air into talus at the base of slope

Front 13

What are the characteristics of slides?

Back 13

- Can be consolidated or unconsolidated material
- Fast
- Material slides as a cohesive mass in contact with slope

Front 14

What are the characteristics of flows?

Back 14

- Can be slow or fast
- Consolidated (rock avalanche) or unconsolidated (debris avalanche) materials
- Material flows over slope

Front 15

What are 2 types of falls?

Back 15

- Rock fall
- Slump

Front 16

What are 4 types of slides?

Back 16

- Debris slide/avalanche
- Rockslide
- Rock avalanche
- Creep

Front 17

What are 3 types of flows?

Back 17

- Earthflow
- Debris flow
- Complex

Front 18

Why is British Columbia vulnerable to mass wasting?

Back 18

- Lots of water content makes slope heavy and makes material less cohesive
- Steep slopes on hills and mountains
- Lots of vegetation on slopes, which can increase the weight

Front 19

What are 3 ways of forecasting mass movements?

Back 19

1. Statistics (distribution of slides and return periods of earthquakes and storms)
2. Monitoring (local sites and satellite)
3. Modelling

Front 20

What are 3 physical interventions for mass movements?

Back 20

1. Slope drainage (removing water) and regrading (making slope less steep)
2. Restraining structures
3. Vegetation to increase cohesion

Front 21

What are 4 ways mass wastings can be avoided?

Back 21

1. Land use restrictions
2. Hazard mapping and zoning
3. Geological and engineering surveys prior to development
4. Insurance

Front 22

What are 6 factors influencing avalanches?

Back 22

1. Slope (~30-45 degrees)
2. Wind depositing loose snow in weak areas, increasing weight
3. Weak snowpack (e.g. hoar)
4. Anchors - whether trees and rocks provide adhesion
5. Temperature variation
6. Accumulation of snowfall

Front 23

What is hoar?

Back 23

Ice crystals deposited on the snowpack when water condenses directly onto ice
- Result in layer weakness in the snowpack

Front 24

What are the 3 zones of an avalanche?

Back 24

1. Startout zone: where avalanche initiated
2. Avalanche track: where avalanche goes down slope
3. Runout area: where avalanche dissipates

Front 25

How are avalanches initiated?

Back 25

- Slab avalanches initiated by overloading slope or zones of weakness in the snowpack at depth
- Point-release avalanches triggered by initial failure of a small amount of snow at the surface

Front 26

How do avalanches move?

Back 26

- Slab avalanches move as a cohesive block initially after the snowpack fractures along a weak layer
- Point-release avalanches start small at the surface and widen as they move downslope

Front 27

What are 3 ways avalanches can be prevented?

Back 27

1. Location planning and zoning
2. Structures in all avalanche zones
3. Control using explosives and forecasting

Front 28

What is a Rutschblock test?

Back 28

Test of snowpack strength by cutting a block of snow and jumping to expose weak layers

Front 29

What are 3 considerations to make before engaging in winter sports?

Back 29

1. Slope angle and orientation
2. Snowpack stability
3. Consequences

Front 30

What is the crest of a wave?

Back 30

The highest point of the wave

Front 31

What is the trough of a wave?

Back 31

The lowest point of a wave

Front 32

What is a wavelength?

Back 32

The distance for one full cycle (i.e. distance between crests or troughs)

Front 33

What is wave height?

Back 33

The vertical distance from crest to trough

Front 34

What is the amplitude of a wave?

Back 34

Half the height (i.e. average height of the wave)

Front 35

What is the steepness of a wave?

Back 35

Height (rise) divided by wavelength (run)

Front 36

What is a wave period?

Back 36

The time for one wavelength to pass a point (e.g. seconds per cycle)

Front 37

What is wave frequency?

Back 37

The number of waves per unit of time (e.g. cycles per second)

Front 38

What is wave celerity?

Back 38

Wavelength divided by period (e.g. 1 meter per second)

Speed

Front 39

What is the relationship between wave period and wave frequency?

Back 39

Wave period is the inverse of wave frequency

Front 40

How is wave speed determined in deep water?

Back 40

Celerity (speed) = wavelength/period

Generally, waves are faster in deep water because wavelengths are longer

Front 41

How is wave speed determined in shallow water?

Back 41

celerity (speed) = 3.1*sqrt(depth)

In shallow water, waves travel slower because less depth

Front 42

What happens to wave speed, wavelength, wave height, and wave period as waves shoal (move into shallower water)?

Back 42

- Wave speed decreases (slows down)
- Wavelengths shorten
- Wave height increases
- Wave period stays the same

Front 43

What are 5 ways a tsunami can be generated?

Back 43

1. Earthquakes
2. Volcanic eruptions
3. Meteor impacts
4. Landslides/mass movements
5. Icebergs falling from glaciers

Front 44

How can earthquakes cause tsunamis?

Back 44

Vertical fault motion (one plate moves over or under another) transmits energy to the water column, resulting in a massive displacement of water

Tsunamis unlikely at strike-slip faults

Front 45

How can volcanoes cause tsunamis?

Back 45

- Land eruption causes landslide into water
- Underwater eruption ejects gas and lava into water

Front 46

How do tsunami waves move in comparison to wind-driven waves?

Back 46

Water flows straight forward over the beach in a highly turbulent state

NOT CIRCULAR like WIND-DRIVEN WAVES

Front 47

What are warning signs of a tsunami?

Back 47

- Trough draws water out (receding sea level)
- Earthquake

Front 48

How can the arrival of a tsunami be predicted?

Back 48

- Predict based on speed, which depends on water depth
- DART buoy system measures pressure changes caused by tsunami moving through ocean

Front 49

Which areas have elevated tsunami risk?

Back 49

Coastal areas near vertical faults, volcanoes and slopes

Front 50

What are the 3 major components that drive a wildfire system?

Back 50

- Fuel (plants degrade into sugar and oxygen when heated; cellulose (sugar) fuels the fire)
- Oxygen
- Heat

Front 51

What are the major stages of a fire?

Back 51

- Preignition stage:
a. Preheating
b. Pyrolysis

- Combustion stage:
a. Flaming combustion
b. Smouldering combustion

Front 52

What happens during the preignition stage of a fire?

Back 52

Fuel (plants) achieves temperature and humidity favorable to ignition

Preheating (fuel loses water and volatiles)

Pyrolysis (heat degrades and splits up larger molecules)

Front 53

What are 3 ways wildfire can ignite?

Back 53

1. Lightning
2. Volcanic activity
3. Human action

Ignition occurs repeatedly as wildfire moves

Front 54

What is flaming combustion?

Back 54

Large visible flames early in the fire at high temperature

Large amount of unburned material

Front 55

What is smoldering combustion?

Back 55

- Takes place at lower temperatures
- Does not require pyrolysis (heat degradation of molecules) for growth

Front 56

How are heat and gas exchanged in a wildfire?

Back 56

- Hot buoyant gases rise, more dense gases are drawn in
- Fire draws in fresh air

Front 57

How does fuel material influence the distribution and extent of fires?

Back 57

- Fuel moisture content varies by location because different types of plants grow in different environments
- The drier the fuel, the easier the wildfire will spread

Front 58

How does topography (i.e. slope) relate to the distribution and extent of wildfires?

Back 58

- South-facing slopes in the Northern Hemisphere have drier fuels and are exposed to prevailing winds that drive the fire upslope

Front 59

How does wind relate to the distribution and extent of wildfires?

Back 59

- Wind preheats unburned materials, spreading the fire
- Winds carry embers to ignite spot fires ahead of the front of the wildfire

Front 60

How does weather relate to the distribution and extent of wildfires?

Back 60

- Hot weather, droughts and low humidity dry out fuel, making ignition more likely

Front 61

What 4 hazards can result from wildfires?

Back 61

1. Destruction of homes and buildings
2. Destruction of forests, grasslands and scrubland
3. Respiratory problems related to smoke
4. Removal of vegetation can increase the risk of rockslides or mudslides because sediment becomes less cohesive

Front 62

What are 2 data collection methods used to manage wildfires?

Back 62

1. Mapping vegetation and potential fuel
2. Weather, Moisture and Precipitation inform Fire Potential Index maps

Front 63

What are 2 fire suppression methods?

Back 63

1. Controlled or prescribed burns to manage forests
2. Reduce fuel for more catastrophic fires (i.e. logging)

Front 64

What 3 generating forces produce waves?

Back 64

1. Gravity (sun & moon) = tides
2. Natural processes (earthquakes, volcanoes, landslides) = tsunami
3. Wind = ripples, chop, swell waves

Front 65

What 2 restoring forces dissipate waves?

Back 65

1. Gravity (majority of restoration)
2. Surface tension

Front 66

What 3 factors determine the growth of wind waves?

Back 66

1. Wind speed (greater speed = greater waves)
2. Wind duration (greater duration = greater waves)
3. Fetch (uninterrupted distance over which wind blows) (greater fetch=greater waves)

Front 67

What is wave interference?

Back 67

When two types of waves interact and cause a more complex wave (i.e. new wave can be increased or decreased in size)

Front 68

What is surf beat?

Back 68

Packets in interfered waves with higher or lower energy than any single wave alone

Front 69

What is constructive interference?

Back 69

Crests of two different types of wave line up to create larger waves

Front 70

What is destructive interference?

Back 70

Crests of one wave type line up with troughs of other wave type to create smaller waves

Front 71

What are rogue waves?

Back 71

Unpredictable and dangerous waves created by constructive interference

Common where a strong current flows against wind-driven waves from storms

Front 72

When do waves break?

Back 72

1. When steepness (height/wavelength) is greater than 1/7 of the wavelength - becomes unstable and collapses

2. When height/depth ~ 3/4 of wavelength crest collapses forward over wave base

Front 73

How is wave energy lost?

Back 73

1. Heat (mixed back into ocean water)
2. Motion of rocks and sediments

Front 74

What are 4 types of shoreline change?

Back 74

1. Erosion
2. Deposit
3. Drown
4. Uplift

Front 75

What is erosion?

Back 75

Process where water saturates sediment on land and material becomes unstable

Material then brought out to sea

Front 76

What is uplifting?

Back 76

Cliffs and bluffs created by tectonically active coasts

Front 77

What is wave refraction?

Back 77

Waves bend around the sides and edges of headlands and arrive nearly parallel to shoreline, carrying eroded materials from headlands to shore

Front 78

What are depositional coastal forms?

Back 78

Sediment deposits along tectonically inactive coasts

Sensitive to change during storms
e.g. Spits and barrier islands

Front 79

What is longshore drift?

Back 79

When waves approach the shore at an angle, eroding some of the beach and migrating the sediment further along the beach

Front 80

What are seawalls?

Back 80

Walls that divide beach to protect from erosion

Problem: beach in front of seawall gets eroded, seawall itself gets eroded and collapses

Front 81

What are groins?

Back 81

Artificial coastal barriers that modify normal sediment transport, causing deposition and erosion in new areas

Front 82

What are jetties?

Back 82

Barriers that are similar to groins, but have an opening to protect an inlet or harbour from deposition

Front 83

What are breakwaters?

Back 83

Structures that intercept waves to protect an area

Front 84

What was the tectonic setting of the Japan earthquake?

Back 84

- Pacific plate and Eurasian plate collision
- Pacific plate subducts under Eurasian plate, compressive stress

Front 85

Why was the Japan earthquake such a large magnitude event?

Back 85

- Elastic stress at plates for over 200 years

Front 86

How did the Japan earthquake generate a tsunami?

Back 86

Eurasian plate releases elastic strain, causing a massive displacement of water upwards in the form of a tsunami

Front 87

If the epicentre was so far off shore, why did the Japan tsunami hit so quickly?

Back 87

Tsunami travel extremely fast in deep ocean; shallow sea floor slows down front of the wave, with fast-moving rear overtaking the front and pushing seawater up

Front 88

What local variable led to variation in the height of the Japan tsunami?

Back 88

Varying depths of the sea bed cause differences in speed

Cliffs, bays and inlets around the shoreline focus and defocus waves

Front 89

If this same type of event happened off of Vancouver Island, would we expect the same type of tsunami? Would Vancouver suffer a similar fate as Sendai?

Back 89

- Cascadia subduction zone building pressure that could rupture
- Could create similar tsunami

Front 90

What precautionary and reactive measures are practiced in Japan that could be implemented in British Columbia?

Back 90

- Automatic earthquake warnings
- Seawalls
- Tsunami drills
- Sirens