Lecture 02-27-2017

Question 1

What are the four main categories of slope failure?

Answer 1

1. Flow - mixing of particles (e.g., earth flow, avalanche, etc.)
2. Slide - particles remain in relative positions to each-other (e.g., translational and rotational land slide, rock slide, etc.)
3. Fall - free fall of fragments (e.g., rockfall)
4. Subsistence (e.g., topple)

Question 2

What are the two types of contrasting geomorphological forces discussed by FS?

Answer 2

1. Driving/action (e.g., gravity).

2. Resisting/reaction (e.g., isostatic uplift).

Question 3

Angle of Repose

Answer 3

The steepest angle at which a sloping surface formed of a particular loose material is stable.

Question 4

How does the Angle of Repose change with particle size?

Answer 4

Finer and rounder particles (e.g., sand) have a lower angle of repose than coarse, irregular particles (e.g., 3/4” clear stone)

Question 5

Relate the two types of contrasting geomorphological forces discussed by FS to the primary causes of land slides.

Answer 5

1. Driving force increase (e.g., saturation by rain).

2. Resisting forces decrease (e.g., undercutting surface).

Question 6

What types of anthropocentric modifications to the geometry of land structures can cause land slides?

Answer 6

1. Excavations and slope modifications (e.g., cut in mountain valleys for the Trans Canada Highway), which causes
2. Overland surface flow changes that exacerbate the underlying causes of instability.

Question 7

How to identify the potential sites of land slide instability?

Answer 7

1. Leaning structures (e.g., trees, telephone poles, buildings, etc.)
2. Bulging retaining walls downslope of earth material

Question 8

What actions can be taken to prevent land slides?

Answer 8

1. Modify drainage
2. Reduce slope angle
3. Erect retaining walls and piles (oftentimes this makes matters worse)

Question 9

Nuée ardente

Answer 9

1. French: “glowing cloud”
2. highly destructive, fast-moving mass
3. of gas-enveloped particles
4. that is associated with certain types of volcanic eruptions.

Question 10

Lahar def. and types.

Answer 10

1. An Indonesian term for a volcanic mudflow.

2. Two types: hot and cold.

Question 11

Turbidity current

Answer 11

An underwater current flowing swiftly downslope owing to the weight of sediment it carries (https://www.youtube.com/watch?v=8gYJJjxY8g0)

Question 12

What is the range of continental (shelf) slope angle?

Answer 12

3 - 10 degrees

Question 13

What are some of the causes of natural subsidence?

Answer 13

1. Fluid withdrawal (e.g., aquifer drainage)

2. Removal of materials (e.g., dissolution of salt deposits by water infiltration)