EOSC 114 EXAM QUESTIONS AND
ANSWERS | 2025 EDITION
How do you monitor Volcanoes? - Answer-Rising magma increases
-swarms of EQ, swelling of the volcano, expulsion of gas
Monitor seismic activity (Look for swarms)
Acoustic Flow Monitors - Detects high frequencies found in lahars
Ground deformation - direct measurements of displacement or tiltmeters or GPS or
inSAR
Gas emissions - Collection or COSPEC/FTIR
Heat flow - Infrared scanning
Why are volcanoes hard to predict? - Answer-Each act differently and while we may
know the rough time of an eruption, we cant say exactly
Distribution of Volcanoes - Answer-Plate Boundaries
Pacific Ring of Fire
Hotspots (where mantle plume rises and intiates melting)
OceanOcean Convergent margins
OceanContienent Convergent Margins
Why study landslides - Answer-Safety
Socioeconomic impact (global warming/pop. increase/use of marginal land)
How are land slides caused - Answer-Caused by mass movement.
Gravity and shear stress specifically (Gravity Perpendicular aka Gp or normal stressand
Tangential gravity Gt)
As Gt increases, Gp decreases and the slope is steeper
When shear stress is greater than shear strength of the slope
-
Shear Strength - Answer-Force that pulls materials downslope. Includes frictional
resistance and cohesion.
Defined as the internal resistance of a body to shear stress
What influences shear strength - Answer-Type of rock
Condition of materials (how eroded)
Presence of structural weakness
pore water pressure within slope
,What is factor of safety - Answer-Fs = Shear strength/shear stress or Resisting/Driving
forces
if Fs > 1 the slope is stable
if Fs < 1 slope failure is expected
Effective Stress - Answer-The sum of contact forces between grains/Total area
Difference between trigger and a cause - Answer-Cause - Creates susceptibility without
initiating
Trigger - Initiates Movement
E.g = EQ, Volcano, raining, removal of veg, loud noises
Trigger Frequency - Answer-How often a trigger causes a landslide
How can erosion cause landslides? What is rapid erosion? - Answer-1) Driving mass
becomes greater than the resisting mass
2)The slope steepness at the base increases such that shear stress > shear strength
3)Rapid erosion is through waves,heavy rainfall and storms
Slope stability + Water Content + Vegetation - Answer-1)Vegetation helps improve
stability by binding loose materials together
2)High levels of water increase a slope's mass and thus increases shear stress
3)Water reduces friction between particles and lower shear strength
4)Changes volume as it get wedged between particles. Volume change can push things
apart.
5) Can make sediment act as fluid
Effect of Seasons on Landslides - Answer-After periods of heavy rain, water affects
erosion rates and content levels and pore pressure. This increases chances of
landslides. This includes periods after snow melts.
Effect of Volcanic Activity on Landslides - Answer-Deposition of volcanic ash on
hillsides can cause intense slides after being triggered by rain for accelerated erosion.
Slope Stability and EQ - Answer-EQ's typically dislodge rocks on steep slopes. They
destabilize slopes and induce more shear stress and weaken the slope overall
Slope stability and people - Answer-Landslides can increase via
1)excavation of a slope at the base or loading at its crest.
2)Deforestation
3)Irrigation
4)Mining
5)Water Leakages
7)Artificial Vibrations
, Classification of Landslides - Answer-Falls
Topples
Slides
Spreads
Flows/Creeps/Debris Flow
Complex Landslides
What is a Fall - Answer-Sudden vertical movement of material.
Extremely fast
What is a Topple - Answer-Forward rotation of materials in the slope
Requires fractured material oriented perpendicular and parallel to the slope face.
What is a slide - Answer-Rotational - Moving down a curved surface
Translational - Moving down a weak plane
What is a Lateral Spread - Answer-Slow/Rapid extensional movement of rock or soil
usually due to sudden liquefaction
What are quick clays? - Answer-Clays that liquefact
What are Flows/Creep/Debris Flow - Answer-Flow - Large amounts of water with soil; it
flows quickly
Creep -A type of flow that flows very slowly
Debris flow - Rapid flow of fully saturated debris in a channel
Debris Avalanche - Rapid shallow flow of partially-fully saturated debris
What are complex landslides? - Answer-Combo of two or more types of landslide types
for example long run out debris flow or sturzstroms.
Starts as rock fall and ends as a debris flow
What are Sturzstroms? - Answer-Dry rock avalanche
Methods of Landslide Mitigation - Answer-Avoidance
Prevention by reducing driving forces
-Removing unstable parts
-Wire Cage to hold mass in place
-Anchors/Meshes
Protection via Rockfalls (control the direction and minimize damage) and barrier
systems
Ways of increasing landslides - Answer-Developing on steeper slopes
Removing veg
Excavation
Altering climate/Water drainage
ANSWERS | 2025 EDITION
How do you monitor Volcanoes? - Answer-Rising magma increases
-swarms of EQ, swelling of the volcano, expulsion of gas
Monitor seismic activity (Look for swarms)
Acoustic Flow Monitors - Detects high frequencies found in lahars
Ground deformation - direct measurements of displacement or tiltmeters or GPS or
inSAR
Gas emissions - Collection or COSPEC/FTIR
Heat flow - Infrared scanning
Why are volcanoes hard to predict? - Answer-Each act differently and while we may
know the rough time of an eruption, we cant say exactly
Distribution of Volcanoes - Answer-Plate Boundaries
Pacific Ring of Fire
Hotspots (where mantle plume rises and intiates melting)
OceanOcean Convergent margins
OceanContienent Convergent Margins
Why study landslides - Answer-Safety
Socioeconomic impact (global warming/pop. increase/use of marginal land)
How are land slides caused - Answer-Caused by mass movement.
Gravity and shear stress specifically (Gravity Perpendicular aka Gp or normal stressand
Tangential gravity Gt)
As Gt increases, Gp decreases and the slope is steeper
When shear stress is greater than shear strength of the slope
-
Shear Strength - Answer-Force that pulls materials downslope. Includes frictional
resistance and cohesion.
Defined as the internal resistance of a body to shear stress
What influences shear strength - Answer-Type of rock
Condition of materials (how eroded)
Presence of structural weakness
pore water pressure within slope
,What is factor of safety - Answer-Fs = Shear strength/shear stress or Resisting/Driving
forces
if Fs > 1 the slope is stable
if Fs < 1 slope failure is expected
Effective Stress - Answer-The sum of contact forces between grains/Total area
Difference between trigger and a cause - Answer-Cause - Creates susceptibility without
initiating
Trigger - Initiates Movement
E.g = EQ, Volcano, raining, removal of veg, loud noises
Trigger Frequency - Answer-How often a trigger causes a landslide
How can erosion cause landslides? What is rapid erosion? - Answer-1) Driving mass
becomes greater than the resisting mass
2)The slope steepness at the base increases such that shear stress > shear strength
3)Rapid erosion is through waves,heavy rainfall and storms
Slope stability + Water Content + Vegetation - Answer-1)Vegetation helps improve
stability by binding loose materials together
2)High levels of water increase a slope's mass and thus increases shear stress
3)Water reduces friction between particles and lower shear strength
4)Changes volume as it get wedged between particles. Volume change can push things
apart.
5) Can make sediment act as fluid
Effect of Seasons on Landslides - Answer-After periods of heavy rain, water affects
erosion rates and content levels and pore pressure. This increases chances of
landslides. This includes periods after snow melts.
Effect of Volcanic Activity on Landslides - Answer-Deposition of volcanic ash on
hillsides can cause intense slides after being triggered by rain for accelerated erosion.
Slope Stability and EQ - Answer-EQ's typically dislodge rocks on steep slopes. They
destabilize slopes and induce more shear stress and weaken the slope overall
Slope stability and people - Answer-Landslides can increase via
1)excavation of a slope at the base or loading at its crest.
2)Deforestation
3)Irrigation
4)Mining
5)Water Leakages
7)Artificial Vibrations
, Classification of Landslides - Answer-Falls
Topples
Slides
Spreads
Flows/Creeps/Debris Flow
Complex Landslides
What is a Fall - Answer-Sudden vertical movement of material.
Extremely fast
What is a Topple - Answer-Forward rotation of materials in the slope
Requires fractured material oriented perpendicular and parallel to the slope face.
What is a slide - Answer-Rotational - Moving down a curved surface
Translational - Moving down a weak plane
What is a Lateral Spread - Answer-Slow/Rapid extensional movement of rock or soil
usually due to sudden liquefaction
What are quick clays? - Answer-Clays that liquefact
What are Flows/Creep/Debris Flow - Answer-Flow - Large amounts of water with soil; it
flows quickly
Creep -A type of flow that flows very slowly
Debris flow - Rapid flow of fully saturated debris in a channel
Debris Avalanche - Rapid shallow flow of partially-fully saturated debris
What are complex landslides? - Answer-Combo of two or more types of landslide types
for example long run out debris flow or sturzstroms.
Starts as rock fall and ends as a debris flow
What are Sturzstroms? - Answer-Dry rock avalanche
Methods of Landslide Mitigation - Answer-Avoidance
Prevention by reducing driving forces
-Removing unstable parts
-Wire Cage to hold mass in place
-Anchors/Meshes
Protection via Rockfalls (control the direction and minimize damage) and barrier
systems
Ways of increasing landslides - Answer-Developing on steeper slopes
Removing veg
Excavation
Altering climate/Water drainage
