Exercise7_Mass Wasting Activity_Spring2021
docx
keyboard_arrow_up
School
East Carolina University *
*We aren’t endorsed by this school
Course
3241
Subject
Geology
Date
Apr 3, 2024
Type
docx
Pages
7
Uploaded by bnlampe02
Dynamic Earth GEOL-1500
Spring 2021
Mass Wasting Events: Mechanisms and Processes
Learning Exercise
Name:_______Bradley Lampe___________
Date: ________03/24/21_________
Learning Goals:
What is the driving force behind mass wasting?
What are the types of mass wasting events?
How is each type of mass wasting event characterized?
What influences slope stability?
What measures can be implemented to protect against mass wasting events?
Questions:
1.
What is the driving force behind mass wasting? What types of material can be transported by mass wasting events?
Gravity is the main driving force behind mass wasting. All types of material can be transported, such as rocks, soil,
clay, and silt. 2.
Name THREE
causes of mass wasting.
1.
Change in slope angle
2.
Weakening of material by weathering 3.
Increased water cocktail
3.
How is North Carolina classified for “landslide severity” as a whole state? Which region of NC has a higher risk of landslides (e.g. North? South? East? West?) and WHY
?
Landslides are most common in the mountain regions of North Carolina because of steep slopes. The Piedmont and
Coastal Plain regions also have landslides that are commonly related to human activity such as making a road cut too steep. 4.
Name this type of mass wasting event: Label the key parts of the image that you used to identify the event. Keep in mind that some mass wasted material may have been transported by the river at the base of the slope!
This could be a flow mass wasting event. The river could have mixed materials with the water, which causes these materials to fall and move at a faster speed. I see there is a lot of soil at the base of the hill. This could have been caused by soil erosion and or excessive amounts of rain, causing the soil to loosen and fall. 1
5.
How are mass wasting movements classified? Give one example of a SLOW event, and one example of a FAST event. Mass wasting events are classified as downhill movement of rock and soil due to gravity. A slow event could
be classified as a not so steep slope and excessive amounts of rain causing soil and rocks from a hill to
slowly trickle down the hill. A fast event could be classified as an avalanche. 6.
Volcanoes have many potential geologic hazards, some of which we have already studied. List three potential hazards, including
one mass wasting hazard related specifically to volcanoes. Describe this new hazard.
Indirect hazards include environmental changes leading to distress, famine, or habitual destruction. One mass wasting event associated with volcanoes are eruptions that occur in Hawaii, as the volcanoes there have been known to be active, destroying local towns. 7.
Two fatal disasters resulting from mass wasting events are described in the slide pack. For EACH, provide the following: Location and date, underlying CAUSE
of the event, type
of event, and number killed.
1952, Gros Ventre, Wyoming. On June 23, a 38 million cubic meter rockslide occurred next to the Gros Ventre river. Large boulder dammed the Gros River and ran up the opposite side of the valley several hundred vertical feet. The dammed river created the landslide, killing six people in a small community. 1959, Madison Canyon, Montana. In 1959, the largest earthquake in Rocky Mountain history struck Hebgen Lake,
Montana. The earthquake caused a rock avalanche that dammed the Madison River. The earthquake killed 28 people. 8.
Mass wasting can occur on land or below sea level. How many
types of submarine mass wasting events are there? Describe
each. Why
do you think submarine events are “well-preserved” in the geologic record?
Singular Slumps
Singular Translation
Multiple-Single type
Complex
2
9.
Define what is an “Angle of Repose”. What features determine the angle of repose for a given material? (List three). Finally, what is the angle of for fine sand vs. angular pebbles?
The Angle of Repose is the steepest angle at which a sloping surface formed of a particular loose material is stable. Features that determine this could be the angle at which the given material sits, where it is, and what kind of material it sits on. The angle of fine sand is far less than the angular pebbled. The pebbles can sit for longer then the sand can because the sand is so fine. 10.
Slope stability determines whether material will move downslope. It is affected by two forces: downslope and resisting. What is the main driver of these two forces?
The main driver of these two forces is gravity. Gravity pulls anything down that is on a slope, eventually forcing it to start sliding or fall down the slope. 11.
One of the causes of mass wasting is excessive rainfall. In terms of the slope stability forces, explain
how rainfall
affects BOTH the downslope and resisting forces, resulting in increased likelihood of slope failure.
In ultimately depends on how much rain the area gets, and what kind of soil is located in that area. If the soil is loose soil such as first or silt, excessive amounts of rainfall will loosen this soil, eventually causing it to wither away and slide, depending on the slope that it’s sitting on. 12.
Imagine a sea-side slope with τ
ff
of 20 kPa. Wave action over-time has removed some material from the base of the slope. Local government is encouraging tourism to the beautiful location and decides to build a hotel at the top of this slope. The combination of natural and anthropogenic actions described here will qualitatively ________
destroy the slope
________ τ (the actual shear stress on the slope), and _______
cause it to collapse
________ F (Factor of Safety). At what value of τ will this slope become unstable?
40 kpa
F= factor of safety, τ
ff = the maximum stress a slope can sustain, τ = the actual shear stress on the slope
13.
Name this type of mass wasting event. Hint: This is a simulation of a sub-sea event!
This is a sea floor landslide, causing much particles from the sea floor to rapidly slide down a slope. 3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
14.
Slope failure triggers can be both natural and anthropogenic (human-induced). Give two examples of natural failure triggers and two examples of anthropogenic failure triggers.
Natural slope triggers include induced rainfall waves hitting the side of a hill. Both of these can cause the soil to become loose with water and become unstable. Anthropogenic failure triggers includes building on unstable slopes and too much tourism, loosening up the soil. 15.
Bed rock geology can greatly influence how and were mass wasting events occur. Give three examples of how different types of geologic configurations can influence the risk of slope failure..
Factors that can trigger slope failure include hydrologic events, rapid snowmelt, progressive soil saturation, increased water pressure, earthquakes, internal erosion, surface or toe erosion, etc. 16.
Both houses A and B are exposed to slope stability hazards. Explain why using specific failure triggers and/or slope stability forces. Give an example of what could be done to mitigate the risk.
House A is in a better situation then House B, but they are still in danger because their house is right below a hill that could eventually be damaged by a landslide caused by constant soil erosion and rainfall on the hill above their house. House B is in the worst scenario because constant rainfall could eventually cause their home to be subject to a landslide because of the sheer stress put on the ground beneath them. Something that could be done to mitigate this risk would be to decrease the slope on the top of the hill for house A, and to reenforce the soil for house B. 4
17.
What are these and what is their purpose?
These things support the hillside making it a stronger structure of rocks. WWWWWWWW
18.
What are some surface features that indicate the development of a slump below the ground? List five
.
Sinkholes, presence of limestone, disappearing streams, deep caves, and loose soil Use the below Landslide Hazard maps from Buncombe county NC to answer questions 19 and 20.
5
6
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
19.
Using the provided maps for Buncombe County, NC, what is common to the areas mapped as “Stable”? What is the minimum Factor of Safety to be considered “Stable”?
All the areas labeled stable are near major roads and highways. This is for safety measures to make sure people aren’t getting injured by mass wasting events. They are also not on slopes. The minimum FS is 1. 20.
Have there been previous slope failures in Buncombe County? How do we know? What is the most common type of mass wasting event to occur in the SW portion of the county?
There have been previous slope failures in Buncombe County. We know because of the type of slopes around the location. We also know there are landslides because of all the hills around the area. Detail from Buncombe County landslide Hazard map
7