what is the significance of the angle of repose in regard to mass wasting?

The 1983 Thistle landslide (foreground) dammed the Spanish Fork River creating a lake that covered the town of Thistle, Utah. The slide covered Hwy 6 and the main railroad between Table salt Lake and Denver.

x Mass Wasting

KEY CONCEPTS

At the finish of this chapter, students should exist able to:

• Explain what mass wasting is and why it occurs on a gradient
• Explicate the basic triggers of mass-wasting events and how they occur
• Identify types of mass wasting
• Identify run a risk factors for mass-wasting events
• Evaluate landslides and their contributing factors

This chapter discusses the central processes driving mass-wasting, types of mass wasting, examples and lessons learned from famous mass-wasting events, how mass wasting can exist predicted, and how people can be protected from this potential take chances. Mass wasting is the downhill motion of stone and soil fabric due to gravity. The term landslide is often used as a synonym for mass wasting, but mass wasting is a much broader terms referring to all movement downslope. Geologically, landslide is a general term for mass wasting that involves fast-moving geologic material. Loose material along with overlying soils are what typically move during a mass-wasting event. Moving blocks of boulder are called rock topples, rock slides, or rock falls, depending on the dominant motility of the blocks. Movements of dominantly liquid textile are called flows. Movement by mass wasting can be slow or rapid. Rapid movement can be dangerous, such as during droppings flows. Areas with steep topography and rapid rainfall, such every bit the California coast, Rocky Mountain Region, and Pacific Northwest, are particularly susceptible to hazardous mass-wasting events.

x.1 Slope Forcefulness

Forces on a block on an inclined plane (fg = forcefulness of gravity; fn = normal strength; fs = shear strength).

Mass wasting occurs when a slope fails. A slope fails when it is likewise steep and unstable for existing materials and weather. Slope stability is ultimately determined past two principal factors: the slope angle and the strength of the underlying fabric. Force of gravity, which plays a part in mass wasting, is abiding on the Earth'south surface for the nigh part, although small variations be depending on the elevation and density of the underlying stone. In the effigy, a block of rock situated on a slope is pulled downward toward the Earth's centre by the force of gravity (fg). The gravitational force interim on a slope can be divided into ii components: the shear or driving forcefulness (fs) pushing the block down the slope, and the normal or resisting strength (fn) pushing into the slope, which produces friction. The human relationship between shear strength and normal forcefulness is called shear strength. When the normal forcefulness, i.e., friction, is greater than the shear force, so the block does non move downslope. However, if the slope bending becomes steeper or if the earth material is weakened, shear strength exceeds normal force, compromising shear forcefulness, and downslope movement occurs.

Equally gradient increases, the force of gravity (fg) stays the aforementioned and the normal force decreases while the shear strength proportionately increases.

In the figure, the strength vectors modify as the gradient angle increases. The gravitational force doesn't change, but the shear force increases while the normal force decreases. The steepest angle at which stone and soil material is stable and volition not movement downslope is called the angle of tranquility. The angle of repose is measured relative from the horizontal. When a gradient is at the angle of quiet, the shear force is in equilibrium with the normal forcefulness. If the slope becomes just slightly steeper, the shear force exceeds the normal force, and the material starts to move downhill. The bending of quiet varies for all fabric and slopes depending on many factors such as grain size, grain limerick, and water content. The figure shows the angle of tranquility for sand that is poured into a pile on a flat surface. The sand grains cascade down the sides of the pile until coming to rest at the angle of tranquillity. At that angle, the base of operations and height of the pile continue to increase, but the angle of the sides remains the same.

Angle of repose in a pile of sand.

Water is a common gene that can significantly modify the shear strength of a detail slope. Water is located in pore spaces, which are empty air spaces in sediments or rocks between the grains. For example, assume a dry sand pile has an angle of repose of 30 degrees. If water is added to the sand, the bending of tranquillity will increment, possibly to lx degrees or fifty-fifty xc degrees, such equally a sandcastle being built at a beach. Only if besides much water is added to the pore spaces of the sandcastle, the h2o decreases the shear strength, lowers the bending of repose, and the sandcastle collapses.

Another factor influencing shear strength are planes of weakness in sedimentary rocks. Bedding planes (meet Chapter 5) can human action as significant planes of weakness when they are parallel to the slope but less so if they are perpendicular to the slope. At locations A and B, the bedding is well-nigh perpendicular to the slope and relatively stable. At location D, the bedding is nigh parallel to the slope and quite unstable. At location C, the bedding is nearly horizontal, and the stability is intermediate between the other two extremes [1]. Additionally, if clay minerals form along bedding planes, they tin absorb water and get slick. When a bedding plane of shale (clay and silt) becomes saturated, it can lower the shear forcefulness of the stone mass and cause a landslide, such as at the 1925 Gros Ventre, Wyoming rock slide. See the case studies section for details on this and other landslides.

Locations A and B take bedding well-nigh perpendicular to the slope, making for a relatively stable slope. Location D has bedding well-nigh parallel to the gradient, increasing the chance of slope failure. Location C has bedding nearly horizontal and the stability is relatively intermediate.

10.ii Mass-Wasting Triggers & Mitigation

Mass-wasting events often have a trigger : something changes that causes a landslide to occur at a specific time. It could exist rapid snowmelt, intense rainfall, earthquake shaking, volcanic eruption, storm waves, rapid-stream erosion, or human activities, such as grading a new road. Increased water content within the slope is the most mutual mass-wasting trigger. Water content tin increase due to rapidly melting snowfall or ice or an intense rain consequence. Intense rain events can occur more than ofttimes during El Niño years. And then, the west coast of North America receives more than precipitation than normal, and landslides go more common. Changes in surface-water atmospheric condition resulting from earthquakes, previous slope failures that dam up streams, or human structures that interfere with runoff, such as  buildings, roads, or parking lots can provide additional h2o to a slope. In the case of the 1959 Hebgen Lake rock slide, Madison Canyon, Montana, the shear strength of the slope may have been weakened by earthquake shaking. Nearly landslide mitigation diverts and drains water away from slide areas.  Tarps and plastic sheeting  are often used to drain water off of slide bodies and prevent infiltration into the slide. Drains are used to dewater landslides and shallow wells are used to monitor the water content of some agile landslides.

An oversteepened slope may also trigger landslides. Slopes can be made excessively steep past natural processes of erosion or when humans modify the landscape for building construction. An case of how a gradient may be oversteepened during development occurs where the bottom of the slope is cutting into, peradventure to build a road or level a building lot, and the superlative of the slope is modified by depositing excavated fabric from below. If done carefully, this practice tin be very useful in land development, just in some cases, this can issue in devastating consequences. For example, this might have been a contributing cistron in the 2014 Northward Table salt Lake City, Utah landslide. A old gravel pit was regraded to provide a route and several edifice lots. These activities may take oversteepened the slope, which resulted in a wearisome moving landslide that destroyed one habitation at the bottom of the slope. Natural processes such as excessive stream erosion from a flood or littoral erosion during a storm tin besides oversteepen slopes. For instance, natural undercutting of the riverbank was proposed as role of the trigger for the famous 1925 Gros Ventre, Wyoming rock slide.

Slope reinforcement can assist forestall and mitigate landslides .  For rockfall-decumbent areas, sometimes information technology is economical to use long steel bolts. Bolts, drilled a few meters into a rock face, can secure loose pieces of textile that could pose a hazard. Shockcrete, a reinforced spray-on form of physical, can strengthen a slope confront when applied properly. Buttressing a slide by calculation weight at the toe of the slide and removing weight from the caput of the slide, can stabilize a landslide.  Terracing, which creates a stairstep topography, can be applied to help with slope stabilization, merely information technology must exist applied at the proper calibration to exist effective.

A different approach in reducing landslide hazard is to shield, catch, and divert the runout textile.  Sometimes the most economical mode to bargain with a landslide gamble is to divert and deadening the falling material.  Special stretchable fencing can be applied in areas where rockfall is common to protect pedestrians and vehicles.  Runout channels, diversion structures, and check dams tin can be used to slow droppings flows and divert them effectually structures.  Some highways take special tunnels that divert landslides over the highway.  In all of these cases the shielding has to exist engineered to a scale that is greater than the slide, or catastrophic loss in property and life could issue.

10.3 Landslide Classification & Identification

Mass-wasting events are classified by blazon of movement and type of material, and in that location are several ways to allocate these events. The effigy and table show terms used. In improver, mass-wasting types often share common morphological features observed on the surface, such as the head scarp—unremarkably seen as crescent shapes on a cliff face; hummocky or uneven surfaces; accumulations of talus—loose rocky material falling from to a higher place; and toe of slope, which covers existing surface material.

x.3.1 Types of Mass Wasting

The nearly common mass-wasting types are falls, rotational and translational slides, flows, and pitter-patter. Falls are precipitous rock movements that disassemble from steep slopes or cliffs. Rocks carve up along existing natural breaks such as fractures or bedding planes. Motion occurs as gratuitous-falling, bouncing, and rolling. Falls are strongly influenced by gravity, mechanical weathering, and water. Rotational slides commonly show slow movement along a curved rupture surface. Translational slides oftentimes are rapid movements along a plane of distinct weakness between the overlying slide fabric and more than stable underlying material. Slides can be farther subdivided into rock slides, debris slides, or earth slides depending on the blazon of the textile involved (see tabular array).

Table of Mass Wasting Types.Mass wasting move type and primary earth textile. Modified from [zotpressInText particular="{948446:KG8X6AAJ},{948446:HN9CI37K}" format="(%num%)" brackets="yes"].

Type of Movement		Primary Material Type and Mutual Name of Slide
		Bedrock	Soil Types
			Mostly Coarse-Grained	Mostly Fine-Grained
Falls		Rock Fall	—	—
Rock Avalanche		Rock Avalanche	—	—
Rotational Slide (Slump)		—	Rotational Debris Slide (Slump)	Rotational Globe Slide (Slump)
Translational Slide		Translational Rock Slide	Translational Debris Slide	Translational Earth Slide
Flows		—	Debris Flow	World menstruation
Soil Creep		—	Pitter-patter	Creep

Examples of some of the types of landslides.

Flows are rapidly moving mass-wasting events in which the loose material is typically mixed with abundant h2o, creating long runouts at the gradient base. Flows are commonly separated into debris flow (fibroid cloth) and earthflow (fine material) depending on the blazon of textile involved and the amount of water. Some of the largest and fastest flows on land are called sturzstroms , or long runout landslides. They are all the same poorly understood, but are known to travel for long distances, even in places without significant atmospheres like the Moon.

Creep is the imperceptibly slow downward movement of cloth acquired by a regular cycle of nighttime freezing followed past daytime thawing in unconsolidated material such every bit soil. During the freeze, expansion of ice pushes soil particles out away from the gradient, while the next mean solar day following the thaw, gravity pulls them directly downward. The internet effect is a gradual motion of surface soil particles downhill. Creep is indicated by curved tree trunks, aptitude fences or retaining walls, tilted poles or fences, and pocket-sized soil ripples or ridges. A special type of soil creep is solifluction, which is the deadening movement of soil lobes on low-angle slopes due to soil seasonally freezing and thawing in high-breadth, typically sub-Chill, Arctic, and Antarctic locations.

Landslide Hazards, David Applegate

x.3.2 Parts of a Landslide

Landslides have several identifying features that can be common across the different types of mass wasting. Note that there are many exceptions, and a landslide does non have to have these features. Displacement of material by landslides causes the absence of fabric uphill and the deposition of new material downhill, and careful observation tin place the evidence of that displacement. Other signs of landslides include tilted or offset structures or natural features that would usually be vertical or in identify.
Many landslides have escarpments or scarps. Landslide scarps, like fault scarps, are steep terrain created when movement of the next land exposes a part of the subsurface. The virtually prominent scarp is the main scarp, which marks the uphill extent of the landslide. Equally the disturbed material moves out of identify, a pace slope forms and develops a new hillside escarpment for the undisturbed material. Chief scarps are formed by motion of the displaced material abroad from the undisturbed ground and are the visible function of slide rupture surface.

The slide rupture surface is the purlieus of the body of movement of the landslide. The geologic textile beneath the slide surface does not move, and is marked on the sides by the flanks of the landslide and at the end by the toe of the landslide.

The toe of the landslide marks the terminate of the moving material. The toe marks the runout, or maximum distance traveled, of the landslide. In rotational landslides, the toe is frequently a large, disturbed mound of geologic material, forming as the landslide moves past its original rupture surface.

Rotational and translational landslides often have extensional cracks, sag ponds, hummocky terrain and pressure ridges. Extensional cracks form when a landslide'due south toe moves forward faster than the rest of landslide, resulting in tensional forces. Sag ponds are small bodies of water filling depressions formed where landslide move has impounded drainage. Hummocky terrain is undulating and uneven topography that results from the basis being disturbed. Pressure ridges develop on the margins of the landslide where material is forced up into a ridge construction.

10.4 Examples of Landslides

Landslides in United States

Scar of the Gros Ventre landslide in background with landslide deposits in the foreground.

1925, Gros Ventre, Wyoming: On June 23, 1925, a 38 million cubic meter (50 million cu yd) translational rock slide occurred next to the Gros Ventre River (pronounced "grow vont") about Jackson Hole, Wyoming. Big boulders dammed the Gros Ventre River and ran upwardly the contrary side of the valley several hundred vertical feet. The dammed river created Slide Lake, and 2 years later on in 1927, lake levels rose loftier plenty to destabilize the dam. The dam failed and acquired a catastrophic flood that killed six people in the small-scale downstream community of Kelly, Wyoming.

Cross-section of 1925 Gros Ventre slide showing sedimentary layers parallel with the surface and undercutting (oversteepening) of the slope by the river.

A combination of three factors acquired the stone slide: 1) heavy rains and apace melting snowfall saturated the Tensleep Sandstone causing the underlying shale of the Amsden Formation to lose its shear forcefulness, 2) the Gros Ventre River cut through the sandstone creating an oversteepened slope, and iii) soil on acme of the mountain became saturated with water due to poor drainage. The cantankerous-section diagram shows how the parallel bedding planes between the Tensleep Sandstone and Amsden Germination offered little friction against the slope surface as the river undercut the sandstone. Lastly, the rockslide may have been triggered by an convulsion.

1959, Madison Canyon, Montana: In 1959, the largest earthquake in Rocky Mountain recorded history, magnitude 7.5, struck the Hebgen Lake, Montana area, causing a destructive seiche on the lake (see Chapter 9). The earthquake caused a stone avalanche that dammed the Madison River, creating Quake Lake, and ran up the other side of the valley hundreds of vertical feet. Today, there are still house-sized boulders visible on the slope opposite their starting indicate. The slide moved at a velocity of up to 160.9 kph (100 mph), creating an incredible air blast that swept through the Rock Creek Campground. The slide killed 28 people, most of whom were in the campground and remain cached there. In a way like the Gros Ventre slide, foliation planes of weakness in metamorphic rock outcrops were parallel with the surface, compromising shear strength.

1959 Madison Canyon landslide scar. Photograph taken from landslide fabric.

1980, Mount Saint Helens, Washington: On May 18, 1980 a five.1-magnitude earthquake triggered the largest landslide observed in the historical record.  This landslide was followed past the lateral eruption of Mountain Saint Helens volcano, and the eruption was followed past volcanic debris flows known as lahars. The volume of fabric moved by the landslide was 2.8 cubic kilometers (0.67 mi^three).

1995 and 2005, La Conchita, California: On March 4, 1995, a fast-moving earthflow damaged ix houses in the southern California coastal customs of La Conchita. A week later, a debris menstruum in the same location damaged 5 more than houses. Surface-tension cracks at the top of the slide gave early warning signs in the summer of 1994. During the rainy winter season of 1994/1995, the cracks grew larger. The probable trigger of the 1995 event was unusually heavy rainfall during the winter of 1994/1995 and ascension groundwater levels. Ten years after, in 2005, a rapid-debris flow occurred at the end of a xv-day menstruation of near-record rainfall in southern California. Vegetation remained relatively intact equally it was rafted on the surface of the rapid flow, indicating that much of the landslide mass simply was beingness carried on a presumably much more saturated and fluidized layer beneath. The 2005 slide damaged 36 houses and killed 10 people.

Oblique LIDAR prototype of La Conchita subsequently the 2005 landslide. Outline of 1995 (blue) and 2005 (yellow) landslides shown; arrows show examples of other landslides in the area; blood-red line outlines main scarp of an aboriginal landslide for the entire bluff. Source: Todd Stennett, Airborne one Corp., El Segundo. Public domain

1995 La Conchita slide. Source: USGS.

2014 Oso slide in Washington killed 43 people and buried many homes (source: USGS, public domain).

2014, Oso Landslide, Washington: On March 22, 2014, a landslide of approximately 18 meg tons (10 million ydⁱⁱⁱ) traveled at 64 kph (40 mph), extended for almost a 1.6 km (1 yard), and dammed the Due north Fork of the Stillaguamish River. The landslide covered forty homes and killed 43 people in the Steelhead Haven community near Oso, Washington. It produced a volume of material equivalent to 600 football game fields covered in material 3 m (x ft) deep. The winter of 2013-2014 was unusually moisture with almost double the average amount of atmospheric precipitation. The landslide occurred in an area of the Stillaguamish River Valley historically active with many landslides, but previous events had been small.

Annotated LiDAR map of 2014 Oso slide in Washington.

Yosemite National Park Stone Falls: The steep cliffs of Yosemite National Park cause frequent stone falls. Fractures created to tectonic stresses and exfoliation and expanded by frost wedging can cause business firm-sized blocks of granite to detach from the cliff-faces of Yosemite National Park.  The park models potential runout, the altitude landslide material travels, to better assess the adventure posed to the millions of park visitors.

Rockfalls in Yosemite.

Utah Landslides

Guess extent of Markagunt Gravity slide.

Markagunt Gravity Slide: Almost 21–22 one thousand thousand years agone, one of the biggest land-based landslides yet discovered in the geologic record displaced more than one,700 cu km (408 cu mi) of material in one relatively fast outcome. Evidence for this slide includes breccia conglomerates (see Affiliate five), glassy pseudotachylytes, (see Chapter vi), slip surfaces (similar to faults) see Chapter 9), and dikes (run across Chapter 7). The landslide is estimated to embrace an surface area the size of Rhode Island and to extend from about Cedar City, Utah to Panguitch, Utah. This landslide was likely the effect of cloth released from the side of a growing laccolith (a blazon of igneous intrusion) see Chapter 4), after existence triggered past an eruption-related earthquake.

The 1983 Thistle landslide (foreground) dammed the Castilian Fork river creating a lake.

1983, Thistle Slide: Starting in April of 1983 and standing into May of that year, a slow-moving landslide traveled 305 m (1,000 ft) downhill and blocked Castilian Fork Canyon with an earthflow dam 61 yard (200 ft) high. This caused disastrous flooding upstream in the Soldier Creek and Thistle Creek valleys, submerging the town of Thistle. As part of the emergency response, a spillway was constructed to prevent the newly formed lake from breaching the dam. After, a tunnel was constructed to bleed the lake, and currently the river continues to menses through this tunnel. The track line and United states-vi highway had to exist relocated at a cost of more than than $200 million.

Business firm before and after destruction from 2013 Rockville rockfall.

2013, Rockville Rock Autumn:Rockville, Utah is a modest customs near the entrance to Zion National Park. In December of 2013, a two,700 ton (1,400 ydⁱⁱⁱ) block of Shinarump Conglomerate fell from the Rockville Demote cliff, landed on the steep 35-degree slope beneath, and shattered into several large pieces that connected downslope at a high speed. These boulders completely destroyed a house located 375 feet below the cliff (see the before and after photographs) and killed two people inside the domicile. The topographic map shows other rock falls in the surface area prior to this catastrophic result.

Tracks of deadly 2013 Rockville rocksfall and earlier documented rockfall events.

2014, North Common salt Lake Slide: In August 2014 after a specially wet period, a deadening moving rotational landslide destroyed one dwelling house and damaged nearby tennis courts .

Scarp and displaced material from the Northward Table salt Lake (Parkview) slide of 2014.

Reports from residents suggested that ground cracks had been seen near the acme of the gradient at to the lowest degree a year prior to the catastrophic movement. The presence of easily-drained sands and gravels overlying more impermeable clays weathered from volcanic ash, forth with recent regrading of the slope,  may have been contributing causes of this slide.  Local heavy rains seem to have provided the trigger.  In the two years after the landslide, the gradient has been partially regraded to increase its stability. Unfortunately, in January 2017, parts of the slope have shown reactivation motility. Similarly, in 1996 residents in a nearby subdivision started reporting distress to their homes.  This distress connected until 2012 when 18 homes became uninhabitable due to extensive  damage and were removed. A geologic park was constructed in the now vacant expanse.

Northward Salt Lake Landslide

2013, Bingham Canyon Copper Mine Landslide, Utah: At nine:xxx pm on April ten, 2013, more than 65 million cubic meters of steep terraced mine wall slid downwardly into the engineered pit of Bingham Canyon mine, making it one of the largest celebrated landslides non associated with volcanoes.  Radar systems maintained by the mine operator warned of movement of the wall, preventing the loss of life and limiting the loss of holding.

10.iv Did I Get It?

Apply this quiz to bank check your comprehension of this section. Click directly on the answer button, non on the answer bar.

ane / 5

1. What happened in the 1925 Gros Ventre slide in Wyoming?

i. An convulsion caused millions of tons of rock to cascade down burying a campground, damming a river, and causing a seiche in a lake.

two. Heavy rains saturated a shale layer causing the already oversteepened slope of rock to slide downward and dam up a river.

3. Blocks of rock fell off a cliff, burial a home and killing two people.

4. Saturated glacial deposits became unstable and flowed downwardly in a valley covering 40 homes and killing 43 people.

5. Slow-moving creep gradually covered a whole boondocks. Though no i died, the structures of Kelly, WY were lost.

Wrong. H2o seeped through sandstone and saturated a shale layer on the oversteepeneed slope causing a slide which dammed the river and formed a lake that broke through two years later flooding downstream towns.

Right! Water seeped through sandstone and saturated a shale layer on the oversteepeneed gradient causing a slide which dammed the river and formed a lake that bankrupt through two years later on flooding downstream towns.

ii / v

two. The 2005 La Conchita slide in California and the 2014 Oso landslide in Washington were both deadly landslides in residential areas. They were principally triggered by ______.

i. Construction

two. Shaking

3. Devegetation

4. Oversteepening of slope

5. Precipitation

Incorrect. Oversaturation of the hillslope caused failure in both of these cases resulting in rapid debris flows.

Correct! Oversaturation of the hillslope caused failure in both of these cases resulting in rapid droppings flows.

three / 5

3. When a landslide  dams a river , what is the greatest ultimate chance?

ane. Saturation from the ascent lake causes deadly droppings flows.

two. The dam produces a rising lake that may overtop the dam, washing information technology out, and causing massive flooding downstream.

three. Water from the river volition saturate the area causing more landslides.

4. Toxic minerals from new rocks and soils exposed by the landslide contaminate the lake and valley.

v. Rising lake water causes even more dangerous mud flows and debris flows.

Wrong. The earthen dam caused by the landslide creates a rising lake that, when it overtops the dam, quickly washes it out creating flooding downstream.

Correct! The earthen dam caused by the landslide creates a rising lake that, when it overtops the dam, quickly washes it out creating flooding downstream.

four / 5

4. The 1959 Madison Canyon landslide killed 28 people near Hebgen Lake. What was the trigger for this landslide?

1. Precipitation

ii. Devegetation

3. Earthquake

4. Oversteepening of slope

5. Construction

Incorrect. This massive landslide was triggered by an earthquake.

Correct! This massive landslide was triggered by an earthquake.

five / 5

5. What is the greatest mass wasting chance to visitors in Yosemite National Park?

ane. Rock falls

2. Debris flows

three. Translational slumps

4. Mud flows

v. Rotational slumps

Incorrect. Rock falls from the steep granitic cliffs is the greatest mass wasting hazard in Yosemite.

Correct! Stone falls from the steep granitic cliffs is the greatest mass wasting run a risk in Yosemite.

10.five Chapter Summary

Mass wasting is a geologic term describing all downhill rock and soil movement due to gravity. Mass wasting occurs when a slope is too steep to remain stable with existing material and conditions. Loose rock and soil, chosen regolith, are what typically move during a mass-wasting event. Slope stability is adamant by two factors: the bending of the gradient and the shear strength of the accumulated materials. Mass-wasting events are triggered by changes that oversteepen gradient angles and weaken gradient stability, such equally rapid snow cook, intense rainfall, earthquake shaking, volcanic eruption, storm waves, stream erosion, and human activities. Excessive precipitation is the nearly common trigger. Mass-wasting events are classified past their type of motility and material, and they share common morphological surface features. The well-nigh common types of mass-wasting events are rockfalls, slides, flows, and creep.

Mass-wasting move ranges from slow to dangerously rapid. Areas with steep topography and rapid rainfall, such equally the California coast, Rocky Mountain Region, and Pacific Northwest, are specially susceptible to hazardous mass-wasting events. By examining examples and lessons learned from famous mass-wasting events, scientists take a better understanding of how mass-wasting occurs. This knowledge has brought them closer to predicting where and how these potentially chancy events may occur and how people tin exist protected.

Affiliate 10 Review

Utilise this quiz to check your comprehension of this chapter. Click directly on the answer push, not on the reply bar.

ane / 10

i. Which of these is NOT a type of mass movement?

1. Menses

2. Slide

three. Creep

four. Transform

5. Fall

Incorrect. Slides, falls, flows, and pitter-patter are all types of mass move. Transform is not a form of mass movement.

Correct! Slides, falls, flows, and creep are all types of mass move. Transform is non a form of mass motion.

ii / 10

ii. Which of these landslides  caused flooding?

ane. Oso Washington

2. Thistle

3. Yosemite Rock Falls

4. Madison Canyon

five. La Conchita

Wrong. In the Thistle slide, a massive flow of earth from a side coulee dammed the Spanish Fork River creating a rising lake that drowned the town of Thistle, Utah.

Right! In the Thistle slide, a massive flow of earth from a side coulee dammed the Castilian Fork River creating a rising lake that drowned the town of Thistle, Utah.

3 / 10

3. When a landslide dams a river in an unpopulated region, what is the main concern?

one. stone avalanches on oversaturated slopes

ii. stone falls from weakened cliffs

3. rotational slumps on submerged slopes

iv. flooding downstream of the earthen dam

five. debris flows from oversaturation on valley walls

Incorrect. The dam forms a rising lake that may overtop the earthen dam, washing it out, and causing mortiferous flooding downstream.

Right! The dam forms a ascent lake that may overtop the earthen dam, washing it out, and causing mortiferous flooding downstream.

4 / 10

4. If you are because a habitation site, what is ane pretty sure evidence of possible landslides affecting the property?

ane. Dramatic geologic structures affecting local strata

2. A history of previous mass wasting events in the area

three. A boiling climate

4. A steep bedding airplane near the site

5. A nearby river

Wrong. Look for a history of previous mass wasting events in the area from undecayed sources similar government geological surveys.

Correct! Wait for a history of previous mass wasting events in the area from dependable sources like government geological surveys.

5 / 10

5. What was the largest known terrestrial landslide?

1. Markagunt gravity slide

2. Thistle landslide

3. Yosemite rock fall

4. Oso debris menses

five. Mt. St. Helens lahar

Incorrect. The largest known terrestrial landslide was the Markagunt Gravity Slide in Utah. Information technology occurred 21-22 million years ago and displaced more than 1700 cubic kilometers of cloth.

Right! The largest known terrestrial landslide was the Markagunt Gravity Slide in Utah. It occurred 21-22 million years ago and displaced more than 1700 cubic kilometers of material.

6 / 10

6. What is solifluction?

one. A rapid form a soil slumping that is very dangerous.

2. Another name for permafrost.

3. Creep of soils downslope caused by wintertime expansion and summertime contraction.

four. Movement of soil lobes on arctic slopes.

5. Saturation of soils by heavy atmospheric precipitation.

Incorrect. Solifluction is movement of soil lobes on slopes due to repeated freezing and thawing in cold chill regions.

Correct! Solifluction is motion of soil lobes on slopes due to repeated freezing and thawing in cold arctic regions.

seven / 10

7. A slump (rotational landslide) is often preceded by ________________?

1. Wide fissures develop in the valley

2. Subsidence is seen at the bottom of the slope

iii. Volcanic eruptions

4. Cracks, possibly with some vertical displacement, occur upslope

5. Several small earthquakes

Incorrect. Cracks may be seen upslope, possibly with some vertical displacement.

Correct! Cracks may be seen upslope, possibly with some vertical displacement.

8 / x

8. Which of these landslides dammed a lake and had an associated destructive seiche?

1. Thistle

ii. Madison Canyon

iii. La Conchita

iv. Yosemite Stone Falls

5. Gros Ventre

Incorrect. The Madison Canyon slide dammed the Madison River. The convulsion that acquired it also caused a seiche in Hebgen Lake which caused considerable devastation.

Correct! The Madison Coulee slide dammed the Madison River. The earthquake that caused it besides caused a seiche in Hebgen Lake which caused considerable devastation.

9 / 10

nine. The number one factor responsible for triggering landslides is ______.

1. human construction

2. convulsion activity

three. saturation of material

4. slump scarp

5. hummocky surface

Wrong. Heavy atmospheric precipitation and saturation of ground is the major trigger of landslides.

Correct! Heavy precipitation and saturation of ground is the major trigger of landslides.

10 / 10

10. Gravity is the force involved in a mass sliding down an inclined aeroplane. Which of these is not related to gravity?

1. Translation

2. Normal

3. Shear

iv. Friction

v. Allure of masses

Wrong. Gravity, resulting from the attraction of masses, can be broken into components, shear and normal, and the normal component contributes to friction. Translation is not a force involved in downslope movement.

Correct! Gravity, resulting from the allure of masses, can be broken into components, shear and normal, and the normal component contributes to friction. Translation is non a strength involved in downslope motion.

References

1. Haugerud, R.A., 2014, Preliminary estimation of pre-2014 landslide deposits in the vicinity of Oso, Washington: US Geological Survey.
2. Highland, Fifty., 2004, Landslide types and processes: pubs.er.usgs.gov.
3. Highland, L.Chiliad., and Bobrowsky, P., 2008, The Landslide Handbook – A Guide to Agreement Landslides: U.Due south. Geological Survey USGS Numbered Series 1325, 147 p.
4. Highland, L.M., and Schuster, R.Fifty., 2000, Significant landslide events in the Us: U.s.a. Geological Survey.
5. Hildenbrand, T.G., and Hendricks, J.D., 1995, Geophysical setting of the Reelfoot rift and relations between rift structures and the New Madrid seismic zone: U.S. Geological Survey Professional Paper 1538-Eastward, 36 p.
6. Hungr, O., Leroueil, Southward., and Picarelli, L., 2013, The Varnes classification of landslide types, an update: Landslides, v. 11, no. 2, p. 167–194.
7. Jibson, R.W., 2005, Landslide hazards at La Conchita, California: United States Geological Survey Open up-File Report 2005-1067.
8. Lipman, P.West., and Mullineaux, D.R., 1981, The 1980 eruptions of Mount St. Helens, Washington: US Geological Survey USGS Numbered Series 1250, 844 p., doi: ten.3133/pp1250.
9. Lund, W.R., Knudsen, T.R., and Bowman, S.D., 2014, Investigation of the December 12, 2013, Fatal Rock Fall at 368 W Chief Street, Rockville, Utah: Utah Geological Survey 273, 24 p.
10. Usa Forest Service, 2016, A Brief History of the Gros Ventre Slide Geological Site: United States Forest Service.

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Source: https://opengeology.org/textbook/10-mass-wasting/

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