Landslides, Mud drifts & Sinkholes

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Description or Situation

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Overview

Finding ourselves in the midst of a land or mud slide is not something we typically visualize happening to such a degree that we plan for a scheduled occurrence, ... unless we work or resided in risky areas prone to such an event. Some regions are certainly self explanatory and reveal their potential characteristics by what we see as obvious or higher risk for human habitation. These are geographical areas that have experienced the same or consistent type events over time and have become known for those characteristics such as with earthquakes or tornado's. Despite the obvious intricacies associated with risky areas people still choose to reside or work within them. Land and mud slides are not limited to the obvious. Additional characteristics which are not as apparent and hidden from view often cause devastating and unexpected surprises. Characteristics as such can cause sink holes large enough to swallow homes and buildings. Land and mud slides have claimed many miles of populated coast line, mountainous regions with towns and low lying areas expectant of overrun from an event occurring in higher regions.  As long as the ground moves beneath our feet and water flows from above or below many regions on planet Earth are subject to anomalous adjustments known as land slides and sink holes.

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The following is intended to present the severity, cause & effects associated with land and mud slides and to provide historical events which validate unsuspected or catastrophic results.

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What is a land or mud slide?

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A landslide, also known as a landslip, is a geological phenomenon that includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows. Landslides can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.

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A landslide is the movement of rock, earth, or debris down a sloped section of land. Landslides are caused by rain, earthquakes, volcanoes, or other factors that make the slope unstableGeologists, scientists who study the physical formations of the Earth, sometimes describe landslides as one type of mass wasting. A mass wasting is any downward movement in which the Earth's surface is worn away. Other types of mass wasting include rockfalls and the flow of shore deposits called alluvium. Near populated areas, landslides present major hazards to people and property. Landslides cause an estimated 25 to 50 deaths and $3.5 billion in damage each year in the United States.

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What are causes for a land or mud slide?

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Landslides occur when the stability of the slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include:

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  Groundwater (pore water) pressure acting to destabilize the slope.

⇒   Loss or absence of vertical vegetative structure, soil nutrients, and soil structure .

  Erosion of the toe of a slope by rivers or ocean waves.

  Weakening of a slope through saturation by snow melt, glaciers melting, or heavy rains.

  Earthquakes adding loads to barely stable slope.

  Earthquake-caused liquefaction destabilizing slopes.

  Volcanic eruptions.

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Landslides can be aggravated by human activities, .... such as

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  Deforestation, cultivation and construction, which destabilize the already fragile slopes.

   Vibrations from machinery or traffic.

   Blasting.

   Earthwork which alters the shape of a slope, or which imposes new loads on an existing slope.

   In shallow soils, the removal of deep-rooted vegetation that binds colluvium to bedrock.

   Construction, agricultural or forestry activities (logging) which change the amount of water which infiltrates the soil.

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Types of landslide

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The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. The materials may move by falling, toppling, sliding, spreading, or flowing. Figure 1 shows a graphic illustration of a landslide, with the commonly accepted terminology describing its features.

The various types of landslides can be differentiated by the kinds of material involved and the mode of movement. A classification system based on these parameters is shown in Figure 2. Other classification systems incorporate additional variables, such as the rate of movement and the water, air, or ice content of the landslide material.

Although landslides are primarily associated with mountainous regions, they can also occur in areas of generally low relief. In low-relief areas, landslides occur as cut-and-fill failures (roadway and building excavations), river bluff failures, lateral spreading landslides, collapse of mine-waste piles (especially coal), and a wide variety of slope failures associated with quarries and open-pit mines. The most common types of landslides are described as follows.

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Slides

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Although many types of mass movements are included in the general term "landslide," the more restrictive use of the term refers only to mass movements, where there is a distinct zone of weakness that separates the slide material from more stable underlying material. The two major types of slides are rotational slides and translational slides.

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Rotational slide

This is a slide in which the surface of rupture is curved concavely upward and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide.

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Translational slide

In this type of slide, the landslide mass moves along a roughly planar surface with little rotation or backward tilting (Figure 3B). A block slide is a translational slide in which the moving mass consists of a single unit or a few closely related units that move down-slope as a relatively coherent mass.

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Falls

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Falls are abrupt movements of masses of geologic materials, such as rocks and boulders, that become detached from steep slopes or cliffs. Separation occurs along discontinuities such as fractures, joints, and bedding planes, and movement occurs by free-fall, bouncing, and rolling. Falls are strongly influenced by gravity, mechanical weathering, and the presence of interstitial water.

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Topples

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Toppling failures are distinguished by the forward rotation of a unit or units about some pivotal point, below or low in the unit, under the actions of gravity and forces exerted by adjacent units or by fluids in cracks.

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Flows

There are five basic categories of flows that differ from one another in fundamental ways.

Debris flow, Debris avalanche, Earthflow, Mudflow & Creep

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Debris flow

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A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilize as a slurry that flows down-slope. Debris flows include <50% fines. Debris flows are commonly caused by intense surface-water flow, due to heavy precipitation or rapid snow-melt, that erodes and mobilizes loose soil or rock on steep slopes. Debris flows also commonly mobilize from other types of landslides that occur on steep slopes, are nearly saturated, and consist of a large proportion of silt- and sand-sized material. Debris-flow source areas are often associated with steep gullies, and debris-flow deposits are usually indicated by the presence of debris fans at the mouths of gullies. Fires that denude slopes of vegetation intensify the susceptibility of slopes to debris flows.

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Debris avalanche 

This is a variety of very rapid to extremely rapid debris flow.

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Earthflow

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Earth-flows have a characteristic "hourglass" shape (Figure 3H). The slope material liquefies and runs out, forming a bowl or depression at the head. The flow itself is elongate and usually occurs in fine-grained materials or clay-bearing rocks on moderate slopes and under saturated conditions. However, dry flows of granular material are also possible.

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Mudflow

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A mud-flow is an earth-flow consisting of material that is wet enough to flow rapidly and that contains at least 50 percent sand-, silt-, and clay-sized particles. In some instances, for example in many newspaper reports, mud-flows and debris flows are commonly referred to as "mudslides."

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Creep

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Creep is the imperceptibly slow, steady, downward movement of slope-forming soil or rock. Movement is caused by shear stress sufficient to produce permanent deformation, but too small to produce shear failure. There are generally three types of creep: (1) seasonal, where movement is within the depth of soil affected by seasonal changes in soil moisture and soil temperature; (2) continuous, where shear stress continuously exceeds the strength of the material; and (3) progressive, where slopes are reaching the point of failure as other types of mass movements. Creep is indicated by curved tree trunks, bent fences or retaining walls, tilted poles or fences, and small soil ripples or ridges.

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Lateral spreads

Damage due to lateral spreads caused by the 2001 Nisqually, WA Earthquake. The length of the damage is approximately 75 feet (225 m). Photo by National Science investigation team.

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Lateral spreads are distinctive because they usually occur on very gentle slopes or flat terrain. The dominant mode of movement is lateral extension accompanied by shear or tensile fractures. The failure is caused by liquefaction, the process whereby saturated, loose, cohesionless sediments (usually sands and silts) are transformed from a solid into a liquefied state. Failure is usually triggered by rapid ground motion, such as that experienced during an earthquake, but can also be artificially induced. When coherent material, either bedrock or soil, rests on materials that liquefy, the upper units may undergo fracturing and extension and may then subside, translate, rotate, disintegrate, or liquefy and flow. Lateral spreading in fine-grained materials on shallow slopes is usually progressive. The failure starts suddenly in a small area and spreads rapidly. Often the initial failure is a slump, but in some materials movement occurs for no apparent reason. Combination of two or more of the above types is known as a complex landslide.

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Land slides in history

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This list of landslides is a list of notable landslides and mud-flows divided into sections by date and type. This list is very incomplete as there is no central catalog for landslides, although some for individual countries/areas do exist. Volumes of landslides are recorded in the scientific literature using cubic kilometers (km3) for the largest and millions of cubic meters (normally given the non-standard shortening of MCM) for most events.

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See a list of land and mud slides here

Landslide Photo Collections

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Landslide Events

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Sink holes

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A sinkhole, also known as a cenote, sink, sink-hole, shake-hole, swallet, swallow hole, or doline (the different terms for sinkholes are often used interchangeably), is a depression or hole in the ground caused by some form of collapse of the surface layer. Some are caused by karst processes—for example, the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes may vary in size from 1 to 600 m (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may be formed gradually or suddenly, and are found worldwide. On 2 July 2015, scientists reported that active pits, related to sinkhole collapses and possibly associated with outbursts, have been found on the comet 67P/Churyumov-Gerasimenko by the Rosetta space probe.

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Natural processes

Sinkholes may capture surface drainage from running or standing water, but may also form in high and dry places in specific locations.

The formation of sinkholes involves natural processes of erosion or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion. For example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void.

Occasionally a sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as the Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park in Kentucky, an underground stream or river may be visible across its bottom flowing from one side to the other.

Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or in other rocks, such as gypsum, that can be dissolved naturally by circulating ground water. Sinkholes also occur in sandstone and quartzite terrains.

As the rock dissolves, spaces and caverns develop underground. These sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.

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Artificial processes

Sinkholes also form from human activity, such as the collapse of abandoned mines and salt cavern storage in salt domes in places like Louisiana, Mississippi and Texas. More commonly, sinkholes occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the over-pumping and extraction of groundwater and subsurface fluids. Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created; the substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.

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Final note

As the earth changes with the passing of time it is inevitable for people to see and/or experience the effects within our life time, ... some more others depending on which cycle the earth may be in. It is also inevitable that societal communities can be impacted by such effects where hindering routine daily life is likely. Being self reliant and prepared for any type of calamity is simple advantageous and conducive for surviving.

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Find  "Solutions to Landslides, Mud drifts & Sinkholes" 

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Videos 

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[ World's Most Killer Landslides Ever Recorded - Full HD Documentary ]

[ Documentary 2015 | Sinkholes ]

[ Eroding cliffs under California residence & homes ]

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Resources

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https://en.wikipedia.org/wiki/Sinkhole

https://en.wikipedia.org/wiki/Landslide

http://landslides.usgs.gov/dysi/form.php

http://www.eoearth.org/view/article/154157/

http://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html

http://education.nationalgeographic.org/encyclopedia/landslide/

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