Microsoft Word - GEOG1106-Lab10_MassMovementKarst.docx
Name: Date:
Mass Movements
***Please submit only this document at the end of the lab period***
INSTRUCTIONS: Please read the lab reader before beginning this exercise. The following lab questions will be based upon the material given in the lab reader.
Part I: Mass Movement Terminology and Types
1. [12%] Complete Table 1 by matching the letters from Figure 1 to a landslide definition.
Figure 1. Example landslide with significant features labeled by letters.
(
PHYSICAL
GEOGRAPHY
LABORATORY
)
Table 1. Landside terminology and definitions.
Definition
Name
Letter (See Figure 1)
The nearly undisplaced material still in place and adjacent to the
highest parts of the main scarp.
Crown
The part of the ground overlain
y the foot of the landslide.
Surface of separation
The portion of the landslide that has moved beyond the toe of surface of rupture and overlies
the original ground surface.
Foot
A steep, nearly vertical upper edge caused by movement of the displaced material. A visible
part of the surface of rupture.
Main scarp
The undisplaced material adjacent to the side of the landslide. If left and right are
used, they are referenced as viewed from the crown.
Right flank
A steep surface on the displaced material produced by differential.
movements within the material.
Minor scarp
The nearly horizontal, upper parts of the landslide along the
contact between the displaced material and the main scarp.
Head
The intersection between the surface of rupture and the
original ground surface.
Toe of surface of rupture
The slope that existed before the
landslide took place.
Original ground surface
The displaced material overlying the surface of rupture between the main scarp and the toe of
surface of rupture.
Main body
A landslide’s lowest end, most
distant from the main scarp.
Toe
The surface that forms the lowe
oundary of the material below the original ground surface.
Surface of rupture
2. [5%] What do all mass movements have in common?
3. [5%] How are development activities by humans related to mass-movement disasters?
4. [5%] What will happen to weathered material when the resistance force is less than the downslope force?
5. [5%] Why are heavy rains of particular concern in areas where mass-movement events are common?
6. [5%] Why are wildfires of particular concern in areas where mass-movement events are common?
7. [6%] Complete Table 2 by matching the letters from Figure 2 to a landslide type.
Figure 2. Several landslide types with important features labeled.
Table 2. Landslide types and descriptions.
Landslide Type
Description
Letter (See Figure 2)
De
is flow
A form of rapid mass movement in which loose soil, rock, and organic matter combine with water to form a slu
y that flows downslope. They have been informally called “mudslides.” Occasionally, a rotational or translational slide may evolve into a de
is flow. Dry flows can sometimes occur in cohesionless sand. De
is flows can be deadly as
they can be extremely rapid and may occur without warning.
Soil creep
Soil creep is the informal name for a slow earth flow. It consists of the imperceptibly slow, steady, downward movement of soil or rock.
Movement is caused by internal shear stress sufficient to cause deformation but insufficient to cause failure.
Rotational landslide
A landslide on which the surface of rupture is curved like a spoon and the slide movement is rotational about an axis parallel to the slope’s contour. The mass may move coherently along the rupture surface with little internal deformation. The head of the displaced material may move almost vertically downward, and the upper surface of the displaced material may tilt backward toward the scarp. If the slide is rotational and has several parallel curved planes of movement, it is
called a slump.
Rockfall
Falls are a
upt, downward movements of rock and/or soil that detach from steep slopes or cliffs. The material often strikes the lower slope at
an angle that causes bouncing. The falling mass may
eak on impact, may roll, and may continue moving until the te
ain flattens.
Lateral spread
Occurs on very gentle slopes, especially where an upper layer of strong rock or soil slides across a lower, softer layer. In rock spreads, solid ground extends and fractures, without necessarily forming a recognizable rupture surface. The underlying softer layer may squeeze
upward into fractures that divide the upper layer into blocks.
Translational landslide
The mass in a translational landslide moves down along a planar surface with little rotational movement or backward tilting. This type of slide may progress over considerable distances if the surface of rupture is sufficiently inclined. The material in the slide may range from loose soils to slabs of rock, or both. Translational slides commonly fail along the contact between rock and soil. In northern environments the slide may
also move along the permafrost layer.
Part II: Triggering Mechanisms
Use Table 1 from the Reader to answer the following questions regarding triggering mechanisms.
8. [2%] What country has suffered the largest number of fatalities from the mass-movement events presented in the table?
9. [2%] What were the two largest mass-movement events in terms of volume, and what was their trigger?
10. [5%] Considering your answer to question 4, explain why the following statement is either co
ect or inco
ect: “The larger the volume of material unleashed during a mass movement event is, the greater is the number of fatalities.”
11. [5%] What Peruvian town was damaged or destroyed twice within a decade, and what would you recommend as a course of action to avoid such an impact in the future?
12. [2%] Are more deaths attributable to the “intense rainfall” trigger or the “volcanic eruption” trigger?
13. [5%] One of the human contributing variables to mass movement is deforestation. What does this activity do to a slope’s stability?
Part III: Measuring Landslides
We will be examining landslides using Google Earth. An example of a region where many landslides have been triggered by a single earthquake (heavy-rain can also trigger landslides) is the Kashmir Earthquake which occu
ed on October 8, 2005. Information on the local area is provided below:
Muzaffarabad, Kashmi
Latitude 34° 24’ 28" N and longitude 73° 28’ 08" E Thousands of landslides resulted due to the earthquake
The government of Pakistan's official death toll was 87,350 due to the earthquake
Find a landslide within this region and follow along the Google Earth guide in the reader to complete the following questions.
14. [3%] What is the location (city, county, country, any landmark, etc)?
15. [3%] Give the latitude and longitude of the location.
16. [5%] Use the "Historical Imagery" tool to see how your landslide has changed with time and provide a historical description in sequence. For example:
- In 1978 te
ain looked normal. No signs of mass movement.
-
17. [2%] Provide approximate date for when the landslide took place.
18. [5%] Calculate the area of the landslide in both square kilometers and square meters.
Obtain a an elevation profile of the te
ain before and after the landslide and:
19. [10%] In the same plot, with two different colors, please sketch the calculated curves for pre and post landslide times. Use a ruler to approximate the te
ain variation. Use distance in the horizontal axis and elevation in the vertical axis.
20. [3%] How are the shapes of slopes before and after the landslide? Describe them
21. [5%] Provide a description of how the landslide changed over time and discuss observations made during the exercise.
Microsoft Word - GEOG1106-Lab11_MassMovementKarst_Reader.docx
PHYSICAL GEOGRAPHY LABORATORY
1
Reader:
Mass Movement and
Surface Karst
Learning Outcomes: This laboratory has the overall objective of exploring the concepts of
mass movement and wasting, as well as the formation of surface karst. After finishing this exercise,
students should be able to classify the variety of landslides and understand their primary features, how
they are formed, and to have an understanding of chemical weathering processes. The specific learning
outcomes are:
1. Describe the process of mass wasting and basic triggering mechanisms.
2. Categorize and identify parts of landslides.
3. Understand and define contributing factors in karst formation.
4. Define and label terminology related to karst diagrams.
Materials: Pencil, lab handout, computer with google earth.
Part I. Mass Movement Mechanisms
Mass movement, or Mass wasting, is the downward movement of material due to the effects of gravity.
When occu
ing suddenly, these events are generally refe
ed to as landslides.
Mass wasting occurs when a slope fails, which happens when the slope is too steep and unstable for
materials to remain on the slope. This can be imagined with a simple block on a ramp where the block is
eing acted on by the force of gravity (fg) that can be decomposed in two cartesian components: a force
perpendicular to the plane of motion, also known as normal force (fn), and another force that is parallel
to the plane of motion (fs). The steepest stable angle is called the angle of repose.
Figure 1. As slope increases, the force of gravity (fg) stays the same and the perpendicular-to-the-plane
component (fn) decreases while the parallel-to-the-plane force (fs) proportionately increases.
PHYSICAL GEOGRAPHY LABORATORY
2
Landslides have common identifying features, including displacement of material with absence of
material uphill and deposition of material downhill. Additional features are provided in the figure below.
Figure 2. An example rotational landslide with a few notable features labeled.
Part II: Triggering Mechanisms
Mass movement events always have a trigger, an event that causes the movement to occur. These
include snowmelt, intense rainfall, earthquake shaking, volcanic eruption, storm waves, rapid-
stream erosion, or human activities. An increase in the water content within the slope is the most
common cause. Additionally, an over-steepened slope- a slope that becomes steeper than the angle of
epose- may form by erosion or human activity which then allows for landslides to occur. Table 1
presents a series of benchmark landslide events that have so far occu
ed in both 20th and 21st centuries.
Table 1. Mass-movement events that occu
ed during the twentieth and twenty-first centuries, all of
which resulted in significant socioeconomic impacts.
Year Location Name and Type Trigger Size Impact
1911 Tajikistan Usoy Rockslide Earthquake 2 x 109 m3
(volume)
54 deaths, Usoy village
destroyed
1919 Indonesia Kelut lahars Volcanic
eruption
Lahars flowed
185 km
5,100 deaths, 104 villages
destroyed or damaged
1920 China Mudflows Earthquake 50,000 km2
covered
100,000 deaths, many
villages buried
1933 China Deixi landslides Earthquake >150 x 106 m3
(volume)
3,000 deaths
PHYSICAL GEOGRAPHY LABORATORY
3
1941 Peru Huaraz De
is Flow Failure of
moraine dam
10 x 106 m3
(volume)
6,000 deaths, 25% of
Huaraz destroyed
1958 Japan Kanogawa
landslides,
mudflows, and
de
is flows
Intense
ainfall
Unknown 1,094 deaths, 19,754
homes destroyed or
damaged
1962 Peru Nevados
Huascaran de
is
avalanche
Unknown 13 x 106 m3
(volume)
5,000 deaths, town of
Ranrahirca destroyed
1970 Peru Nevados
Huascaran de
is
avalanche
Earthquake 50 x 106 m3
(volume)
18,000 deaths, town of
Yungay destroyed, town
of Ranrahirca partially
destroyed
1985 Colombia Nevado del Ruiz
de
is flows
Volcanic
eruption
Unknown 23,000 deaths, 4 towns
destroyed
1999 Venezuela Landslides and
de
is flows
Intense
ainfall
Unknown 30,000 deaths, hundreds
of buildings and roads
destroyed
2005 Pakistan/India Landslides,
ockfalls, and rock
avalanches
Earthquake Unknown 25,500 deaths
2010 Brazil De
is flows Rain Unknown 350 deaths, 61 houses
destroyed
Credit/courtesy of USGS (adapted)
Part III: Measuring Landslides
In this part, we will demonstrate how to measure the area of a landslide (and observe its change over
time, and its profile) using Google Earth. We will use, as an example, a landslide from Hattian Bala,
Kashmir. Later, in Section 3, you will be given three examples of regions where landslides have occu
ed
that you can explore using Google Earth. The Hattian Bala landslide that we will use, was one of many
thousand landslides (mainly rock falls and rock slides) triggered by the Kashmir earthquake which
occu
ed on 8 October 2005. The landslide buried the village of Dandbeh. We will look at the Hattian
Bala landslide and try to answer some basic questions. Finally, we will prepare a report on few landslides
(other than Hattian Bala).
Search:
Enter the name of location (Hattian Bala in this case) in the Search panel (top left) and click Search. The
Google earth will automatically zoom to Hattian Bala, a small town near the Indo-Pak border. Zoom out
a bit and you will see a big landslide to the south of Hattian Bala (see Figure 3).
PHYSICAL GEOGRAPHY LABORATORY
4
Figure 3. Snapshot of the big mass wasting occu
ed near Hattian Bala.
Identify the coordinates, elevation, and eye altitude:
Move your cursor to the location and you will see that the latitude and longitude are displayed in the
ottom right corner (Figure 4).
Figure 4. Date, location and eye altitude information in Google Earth.
PHYSICAL