Rockslide

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Rockslide at Oddicombe Beach in Devon, UK Rockslide at Oddicombe.jpg
Rockslide at Oddicombe Beach in Devon, UK

A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses en masse and not in individual blocks. Note that a rockslide is similar to an avalanche because they are both slides of debris that can bury a piece of land. While a landslide occurs when loose dirt or sediment falls down a slope, a rockslide occurs only when solid rocks are transported down slope. The rocks tumble downhill, loosening other rocks on their way and smashing everything in their path. [1] Fast-flowing rock slides or debris slides behave similarly to snow avalanches, and are often referred to as rock avalanches or debris avalanches. [2]

Contents

Definition

The term landslide refers to a variety of mass wasting events (geologic slope failures) that include slumps, slides, falls, and flows. The two major types of slides are rotational slides and translational slides. [3] Rockslides are a type of translational event since the rock mass moves along a roughly planar surface with little rotation or backward tilting. [3] Rock slides are the most dangerous form of mass-wasting because they incorporate a sudden, incredibly fast-paced release of bedrock along a uniform plane of weakness. These uniform weaknesses are key to identifying rock slides because unlike slumps, flows, or falls, the failed material moves in a fairly uniform direction over a layer of solid, pre-existing rock. Rock may break down while falling during rockslides.

The sudden, rapid release of material found in rock slides combined with the sheer size and weight of the material that is falling is what gives these events the potential to have devastating effects on human life and infrastructure. Rock slides are very common in the over steepened canyons and drainages of Idaho, particularly in those areas like the Salmon River Canyon where more than 5,000 feet of elevation may exist between the ridge tops and the canyon bottoms. [4]

Causes

Mass-wasting occurs whenever the gravitational force on the rock exceeds the ability of the slope to resist that force. Therefore, anything that erodes or impedes the mountain's ability to resist this force may be one of the causes of mass-wasting. [5] While a major event such as an earthquake can cause large rockslides to happen, a majority of slides occur due to a combination of gravitational pressure and erosional influences. Anthropogenic activities, such as altering the geometry of a hill through excavation, can also change the stress state, contributing to slope instability [6] .

Amongst these erosional properties, water is arguably the most effective geologic agent that causes mass-wasting events to occur. Water aids in the downslope movement of surface material by adding weight to the soil and by filling pores which tends to push apart individual grains, decreasing the resistance of the material to movement. [4] While these processes can cause a slide to happen, the speed and potential devastation of a rockslide is often determined by the severity of steepness presented by the failing slope.

Disaster prevention

With increasing populations in rural areas around the world, the hazards presented by potential rock slides are becoming more of a pressing issue moving forward. Luckily, individuals working in the fields of geologic science and engineering continue to perfect methods of rock slide detection, assessment, and warning. New earth observation tools have supplied a much enhanced ability to detect potential rock slide hazards. Analysis of sequential InSAR and LiDAR data provides a very valuable regional view of slope movement. [7] Once susceptible areas are discovered, detailed analysis can be carried out at the specific site. These assessments are used to determine the amount of material that will be released as well as the speed at which this material will be transported.

Once a site is deemed hazardous, different types of geologic engineering techniques are used in order to prevent the compromised slope from failing. Some of these designs are listed below.

Wire meshing
A corrosion resistant material that is installed at the crest and foot of the slope. This insures that any falling debris is trapped behind the mesh.
Retaining walls
One of the oldest forms of ground engineering, retaining walls are built in order to neutralize the effects of unstable slopes by holding fallen rocks and soil back from roads and other structures.
Soil nailing
An economical method of constructing a form of retaining wall from the top of a slope down. In this process closely spaced steel tendons are drilled into the soil. These nails significantly increase the cohesion of soil through the ability of these rods to carry tensile loads. these steel beams are usually reinforced through the use of welded wire mesh.
Rock bolting
Rock bolts are always a primary means of reinforcement, Bolts are placed in a specific pattern in order to transfer the faces load from the slopes exterior, to its interior.

See also

Related Research Articles

<span class="mw-page-title-main">Erosion</span> Natural processes that remove soil and rock

Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.

<span class="mw-page-title-main">Landslide</span> Natural hazard involving ground movement

Landslides, also known as landslips, or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides.

<span class="mw-page-title-main">Slump (geology)</span> Short distance movement of coherent earth down a slope

A slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or a rock layer moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface. Causes of slumping include earthquake shocks, thorough wetting, freezing and thawing, undercutting, and loading of a slope.

<span class="mw-page-title-main">Engineering geology</span> Application of geology to engineering practice

Engineering geology is the application of geology to engineering study for the purpose of assuring that the geological factors regarding the location, design, construction, operation and maintenance of engineering works are recognized and accounted for. Engineering geologists provide geological and geotechnical recommendations, analysis, and design associated with human development and various types of structures. The realm of the engineering geologist is essentially in the area of earth-structure interactions, or investigation of how the earth or earth processes impact human made structures and human activities.

<span class="mw-page-title-main">Geological hazard</span> Geological state that may lead to widespread damage or risk

A geologic hazard or geohazard is an adverse geologic condition capable of causing widespread damage or loss of property and life. These hazards are geological and environmental conditions and involve long-term or short-term geological processes. Geohazards can be relatively small features, but they can also attain huge dimensions and affect local and regional socio-economics to a large extent.

<span class="mw-page-title-main">Mass wasting</span> Movement of rock or soil down slopes

Mass wasting, also known as mass movement, is a general term for the movement of rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in a moving medium, such as water, wind, or ice. Types of mass wasting include creep, solifluction, rockfalls, debris flows, and landslides, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, Jupiter's moon Io, and on many other bodies in the Solar System.

<span class="mw-page-title-main">Submarine canyon</span> Steep-sided valley cut into the seabed of the continental slope

A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km (3 mi), from canyon floor to canyon rim, as with the Great Bahama Canyon. Just as above-sea-level canyons serve as channels for the flow of water across land, submarine canyons serve as channels for the flow of turbidity currents across the seafloor. Turbidity currents are flows of dense, sediment laden waters that are supplied by rivers, or generated on the seabed by storms, submarine landslides, earthquakes, and other soil disturbances. Turbidity currents travel down slope at great speed, eroding the continental slope and finally depositing sediment onto the abyssal plain, where the particles settle out.

<span class="mw-page-title-main">Rockfall</span> Rocks fallen freely from a cliff, roof, or quarry

A rockfall or rock-fall is a quantity/sheets of rock that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or walls of mine or quarry workings. "A rockfall is a fragment of rock detached by sliding, toppling, or falling, that falls along a vertical or sub-vertical cliff, proceeds down slope by bouncing and flying along ballistic trajectories or by rolling on talus or debris slopes."

<span class="mw-page-title-main">Hilina Slump</span> Subsided section of the Big Island of Hawaii

The Hilina Slump, on the south flank of the Kīlauea Volcano on the southeast coast of the Big Island of Hawaiʻi, is the most notable of several landslides that ring each of the Hawaiian Islands. These landslides are the means by which material deposited at a volcano's vents are transferred downward and seaward, eventually spilling onto the seabed to broaden the island.

<span class="mw-page-title-main">Mudflow</span> Form of mass wasting

A mudflow, also known as mudslide or mud flow, is a form of mass wasting involving fast-moving flow of debris and dirt that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significant proportion of clay, which makes them more fluid than debris flows, allowing them to travel farther and across lower slope angles. Both types of flow are generally mixtures of particles with a wide range of sizes, which typically become sorted by size upon deposition.

<span class="mw-page-title-main">Rock glacier</span> Glacial landform

Rock glaciers are distinctive geomorphological landforms, consisting either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in-between. Rock glaciers are normally found at high latitudes and/or elevations, and may extend outward and downslope from talus cones, glaciers or terminal moraines of glaciers.

<span class="mw-page-title-main">Sturzstrom</span> Type of landslide

A Sturzstrom or rock avalanche is a large landslide, consisting of soil and rock. It travels a great horizontal distance, compared to its initial vertical drop. Sturzstroms have similarities to the flow of glaciers, mudflows, and lava flows. They flow across land fairly easily, and their mobility increases when volume increases. They have been found on other bodies in the Solar System, including the Moon, Mars, Venus, Io, Callisto, Iapetus, and Phobos.

<span class="mw-page-title-main">2006 Southern Leyte mudslide</span> Major landslide in the Philippines

On February 17, 2006, a massive rock slide-debris avalanche occurred in the Philippine province of Southern Leyte, causing widespread damage and loss of life. The deadly landslide followed a 10-day period of heavy rain and a minor earthquake. The official death toll was 1,126.

There have been known various classifications of landslides. Broad definitions include forms of mass movement that narrower definitions exclude. For example, the McGraw-Hill Encyclopedia of Science and Technology distinguishes the following types of landslides:

<span class="mw-page-title-main">Submarine landslide</span> Landslides that transport sediment across the continental shelf and into the deep ocean

Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress exceeds the resisting stress of the seafloor slope material, causing movements along one or more concave to planar rupture surfaces. Submarine landslides take place in a variety of different settings, including planes as low as 1°, and can cause significant damage to both life and property. Recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology.

A tsunami is a series of water waves caused by the displacement of a large volume within a body of water, often caused by earthquakes, or similar events. This may occur in lakes as well as oceans, presenting threats to both fishermen and shoreside inhabitants. Because they are generated by a near field source region, tsunamis generated in lakes and reservoirs result in a decreased amount of warning time.

<span class="mw-page-title-main">2014 West Salt Creek landslide</span>

The West Salt Creek landslide occurred on the evening of May 25, 2014 near Collbran, Colorado, along the north side of the Grand Mesa, about 30 miles (48 km) east of Grand Junction. It was the largest landslide in Colorado's history.

<span class="mw-page-title-main">2010 Mount Meager landslide</span> 2010 landslide in British Columbia, Canada

The 2010 Mount Meager landslide was a large catastrophic debris avalanche that occurred in southwestern British Columbia, Canada, on August 6 at 3:27 a.m. PDT (UTC-7). More than 45,000,000 m3 (1.6×109 cu ft) of debris slid down Mount Meager, temporarily blocking Meager Creek and destroying local bridges, roads and equipment. It was one of the largest landslides in Canadian history and one of over 20 landslides to have occurred from the Mount Meager massif in the last 10,000 years.

<span class="mw-page-title-main">Mount Cayley</span> Mountains in British Columbia

Mount Cayley is an eroded but potentially active stratovolcano in the Pacific Ranges of southwestern British Columbia, Canada. Located 45 km (28 mi) north of Squamish and 24 km (15 mi) west of Whistler, the volcano resides on the edge of the Powder Mountain Icefield. It consists of massif that towers over the Cheakamus and Squamish river valleys. All major summits have elevations greater than 2,000 m (6,600 ft), Mount Cayley being the highest at 2,385 m (7,825 ft). The surrounding area has been inhabited by indigenous peoples for more than 7,000 years while geothermal exploration has taken place there for the last four decades.

<span class="mw-page-title-main">Volcanic landslide</span> Mass movement that occurs at volcanoes

A volcanic landslide or volcanogenic landslide is a type of mass wasting that takes place at volcanoes.

References

  1. Whittow, John (1984). Dictionary of Physical Geography. London: Penguin, 1984. ISBN   0-14-051094-X.
  2. "Flows". California State University Long Beach. Archived from the original on 2013-08-18.
  3. 1 2 "Landslide Types and Processes". USGS. 2004-08-18. Retrieved 2015-12-17.
  4. 1 2 "What is Mass Movement?". Idaho Museum of Natural History. Retrieved 2015-12-17.
  5. "Types of Wasting: Slump, Rockslide, Debris Flow & Earthflow - Video & Lesson Transcript" . Study.com. Retrieved 2015-12-17.
  6. Tomás, Roberto; Pinheiro, Marisa; Pinto, Pedro; Pereira, Eduardo; Miranda, Tiago (2023-08-01). "Preliminary analysis of the mechanisms, characteristics, and causes of a recent catastrophic structurally controlled rock planar slide in Esposende (northern Portugal)". Landslides. 20 (8): 1657–1665. Bibcode:2023Lands..20.1657T. doi:10.1007/s10346-023-02082-y. ISSN   1612-5118.
  7. D. Jean Hutchinson (2008). "Rock slide hazards: Detection, assessment and warning". Geological Survey of Brazil. Retrieved 2015-12-17.