Mass Wasting and Landslides Part 2
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Questions and Answers

FLUVIAL EROSION is caused by flowing ______.

water

WEATHERING involves breaking down ROCKS and ______ on Earth’s surface.

MINERALS

EROSION typically implies that worn-down materials are ______ away.

transported

A LANDSLIDE can be defined as the failure and downslope movement of rock or ______ materials due to gravity.

<p>unconsolidated</p> Signup and view all the answers

Mass wasting refers to the movement of mass down a ______ due to gravity.

<p>slope</p> Signup and view all the answers

A SLUMP occurs above a curved ______.

<p>slope</p> Signup and view all the answers

CREEP is characterized by very slow movement of soil and ______ materials.

<p>unconsolidated</p> Signup and view all the answers

Mass of unconsolidated material can move downward and spread ______.

<p>outward</p> Signup and view all the answers

The presence of excess ______ can often cause a SLUMP to occur.

<p>water</p> Signup and view all the answers

FLOWS can range from extremely slow to extremely ______.

<p>rapid</p> Signup and view all the answers

CREEP results in cracked ______ due to the gradual movement of materials.

<p>roads</p> Signup and view all the answers

SLIDES can be categorized as SLUMP and various types of ______.

<p>flows</p> Signup and view all the answers

CREEP is prevalent on ______ surfaces.

<p>sloped</p> Signup and view all the answers

FALLS are an EXTREMELY RAPID or VERY RAPID form of ______

<p>mass wasting</p> Signup and view all the answers

ROCKFALLS and SOIL FALLS can also be driven by HYDROSTATIC PRESSURE and the presence of water in ______ cracks.

<p>bedrock</p> Signup and view all the answers

A rock slide buries ______.

<p>equipment</p> Signup and view all the answers

SLUMP is sliding encountered when a thick layer/slice of ______ material is on a curved slope.

<p>unconsolidated</p> Signup and view all the answers

ROCK AVALANCHES involve larger rocks moving downhill quickly, fragmenting to form smaller ______.

<p>rocks/pieces</p> Signup and view all the answers

The mass of UNCONSOLIDATED MATERIAL moves DOWNWARD and spreads ______.

<p>outward</p> Signup and view all the answers

Erosion by rivers/streams and wave action below is also known as ______.

<p>undercutting</p> Signup and view all the answers

A curved trunk is known as a ______.

<p>pistol butt</p> Signup and view all the answers

Mass wasting is generally associated with ______ materials.

<p>unconsolidated</p> Signup and view all the answers

Creep can be enhanced by frozen subsoil preventing water ______.

<p>drainage</p> Signup and view all the answers

Solifluction is creep triggered by freeze-thaw in ______ climates.

<p>colder</p> Signup and view all the answers

Mudflows and debris flows can have extremely ______ movement of unconsolidated materials.

<p>rapid</p> Signup and view all the answers

Mudflow is the flow of (water) saturated unconsolidated material whose grains are ______-sized or smaller.

<p>sand</p> Signup and view all the answers

Debris flow refers to saturated unconsolidated material with grains that are ______-sized or larger.

<p>gravel</p> Signup and view all the answers

Soil particles vary in ______.

<p>size</p> Signup and view all the answers

CLAY particles are smallest with DIAMETERS less than ______ mm.

<p>0.002</p> Signup and view all the answers

SILT particles have DIAMETERS ranging from ______ mm to 0.05 mm.

<p>0.002</p> Signup and view all the answers

SAND particles have DIAMETERS ranging from 0.05 mm to ______ mm.

<p>2.0</p> Signup and view all the answers

PORE SIZE is largest in ______ and smallest in CLAY.

<p>GRAVEL</p> Signup and view all the answers

DEBRIS FLOWS involve movement of LARGER particles than ______.

<p>MUDFLOWS</p> Signup and view all the answers

UNCONSOLIDATED MATERIAL can become ______ which causes it to FLOW with water.

<p>SATURATED</p> Signup and view all the answers

Volcanic activity can suddenly melt ______, leading to mass wasting.

<p>ice/snow</p> Signup and view all the answers

When soil is completely filled with water, it is said to be ______.

<p>SATURATED</p> Signup and view all the answers

A LAHAR is a flowing mixture of water, debris, volcanic and ______ materials.

<p>unconsolidated</p> Signup and view all the answers

TOPPLING involves the forward ______ and movement of a mass out of a slope.

<p>rotation</p> Signup and view all the answers

Undercutting causes erosion of material at the foot of a ______ or steep slope.

<p>cliff</p> Signup and view all the answers

The formation of a ______ cone occurs when debris piles up at the base of a slope.

<p>talus</p> Signup and view all the answers

Mass wasting can occur extremely ______ to rapidly due to various triggering factors.

<p>slowly</p> Signup and view all the answers

LAHAR is classified as a type of ______ flow associated with volcanic activity.

<p>debris</p> Signup and view all the answers

Factors such as ice/snow thaw and ______ contribute to mass wasting events.

<p>weathering</p> Signup and view all the answers

Erosion is a geological process in which materials are worn away and potentially transported by ______ or water.

<p>wind</p> Signup and view all the answers

Flashcards

Erosion vs. Weathering

Erosion is the wearing down and transportation of materials, while weathering is the wearing down of materials without transport.

Landslide

The failure and downslope movement of rock or unconsolidated material due to gravity.

Fluvial Erosion

Erosion caused by flowing water

Mass Wasting

Downslope movement of rock or unconsolidated material due to gravity.

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Weathering Factors

Water, ice, acids, salts, plants, animals, and temperature changes break down rocks and minerals.

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Rockfall

A very rapid form of mass wasting involving rocks.

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Soil fall

A very rapid form of mass wasting involving unconsolidated materials (like soil).

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Hydrostatic pressure

Pressure exerted by water that can trigger mass wasting.

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Rock slide

A form of mass wasting where rocks move along a slope, ranging from very slow to moderately fast.

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Rock avalanche

A rapid form of rock mass wasting where large rocks break down and move quickly down a slope.

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Slump

A mass wasting event where a thick layer of unconsolidated material moves downward and outward along a curved slope.

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Mass wasting (slides)

The downslope movement of rock and/or soil.

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Undercutting

Erosion below a slope that can trigger mass wasting.

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Slump (Unconsolidated Material Slide)

A type of landslide where a thick layer of unconsolidated material slides down and spreads outward along a curved slope.

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Unconsolidated material

Material that hasn't been cemented or compacted together. Examples include soil and loose sediment.

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Curved slope

A slope with a curved shape.

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Creep

Very slow movement of soil or unconsolidated material down a slope, difficult to distinguish from sliding.

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Slide (Landslide)

A form of mass wasting that involves the rapid movement of rock or unconsolidated material. It can range from extremely slow to extremely rapid.

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Flow (Mass Wasting)

A form of mass wasting that involves the movement of unconsolidated materials. It can range from extremely slow to extremely rapid.

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Excess water

More water than is stable for the given material and conditions.

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Pistol Butt

A curved trunk of a tree that leans downhill, often found in trees due to the effects of gravity.

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What causes creep?

Creep is the slow, downhill movement of soil, often enhanced by factors such as frozen subsoil preventing water drainage (leading to wet material above), freeze-thaw cycles, and frequent wetting/drying of the soil.

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Solifluction

A type of creep triggered by freeze-thaw cycles in colder climates, resulting in the gradual movement of wet soil or unconsolidated materials downslope.

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Mudflow

A rapid to extremely rapid flow of water-saturated unconsolidated material (soil, sediment) downslope, where the material is sand-sized or smaller.

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Debris Flow

A rapid to extremely rapid flow of water-saturated unconsolidated material downslope, where the material is gravel-sized or larger.

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What makes mudflows and debris flows possible?

Mudflows and debris flows occur when sediment or unconsolidated materials become saturated with water, often due to heavy rain, ice/snow thaw, or other factors. This saturation weakens the material, making it lose its ability to hold together and allowing it to flow downhill.

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Mudflow vs. Debris Flow

Both mudflows and debris flows are rapid flows of water-saturated material. The difference lies in the size of the sediment particles: Mudflows consist of sand-sized particles or smaller, while debris flows contain gravel-sized particles or larger.

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Can mudflows happen on gentle slopes?

Yes, mudflows can occur even on gentle slopes due to the high water saturation of the soil, which reduces its ability to resist downslope movement.

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Lahar

A fast-moving flow of water, volcanic debris, and other materials, often triggered by volcanic activity.

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What triggers a lahar?

Lahars can be triggered by volcanic eruptions, heavy rainfall, or even the melting of snow and ice on a volcano's slopes.

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Topple

A type of mass wasting where a mass of rock or unconsolidated material rotates and moves downslope.

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What causes a topple?

Topples can be caused by factors like weathering, undercutting, ice thaw, and fluvial erosion.

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Talus cone

A pile of loose rock and debris at the base of a slope, often formed by toppling and other mass wasting events.

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Erosion

The process of wearing away and transporting materials by natural forces like wind or water.

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Debris

Loose, naturally occurring material, mostly broken pieces of rock.

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Soil Particle Size

Refers to the different sizes of soil particles, categorized as gravel/stones, sand, silt, and clay, each with specific diameter ranges.

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Clay Particles

The smallest soil particles with diameters less than 0.002 mm. They are responsible for water retention and soil structure.

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Silt Particles

Soil particles with diameters ranging from 0.002 mm to 0.05 mm. They have moderate water retention and can contribute to a fine texture.

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Sand Particles

Soil particles with diameters ranging from 0.05 mm to 2.0 mm. They allow good water drainage and are gritty to touch.

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Gravel/Stones

The largest soil particles with diameters greater than 2.0 mm. They don't contribute significantly to soil structure.

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Pore Space

The empty spaces that exist between soil particles, affecting water flow and soil aeration.

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Pore Size

The size of the spaces between soil particles, influencing water flow and drainage.

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Saturated Soil

Soil that has all its pore spaces filled with water, making it waterlogged.

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Study Notes

Mass Wasting/Landslides Part 2

  • Mass wasting (slope failure) is the failure and downslope movement of rock or unconsolidated materials due to gravity.
  • Unconsolidated materials are derived from the disintegration and erosion of rocks on the land's surface, including clay, silt, sand, and gravel.
  • Mass wasting examples include rocks and unconsolidated materials.

Fall vs. Slide vs. Flow

  • Fall: Material drops through air, vertically.
  • Slide: Material moves as a mass along a sloping surface with no internal motion.
  • Flow: Material moves downslope with internal motion, like a fluid (water, lava).
  • Most mass wasting examples include two or more of these. For example, stones can slide before falling off a cliff.

Mass Wasting: Falls

  • Falls are a very rapid or extremely rapid form of mass wasting seen with rocks (rockfalls) and unconsolidated materials (soil falls).
  • Rockfalls involve rapid downslope movement of dislodged rocks originating above a steep slope.
  • Rocks may experience falling, rolling, bouncing, and/or sliding. Falling rocks can include broken chunks from bedrock outcrops or boulders coming down mountainsides/cliffs.
  • Rockfalls have varying rates of movement, from extremely rapid to extremely slow.
  • Factors influencing rockfalls include joints opening (due to pressure, frost, or roots wedging), and removal of support (river erosion, quarrying, or wave action).

Mass Wasting: Falls (Definitions)

  • Bedrock: Hard, solid rock (consolidated rock) beneath unconsolidated materials like soil, sand, or gravel; can extend hundreds of meters below the Earth's surface.
  • Outcrops: Visible exposures of bedrock due to erosion or tectonic plate activity.
  • Hydrostatic Pressure: Pressure of any fluid (e.g., water) in a confined space.

Mass Wasting: Falls (Additional Factors)

  • Rockfalls and soil falls can be influenced by shear force, shear strength, rock strength, hydrostatic pressure, and the presence of water in bedrock cracks.
  • Freeze-thaw cycles, heavy snowfall, plant roots in cracks, and undercutting (erosion by rivers/streams or wave action) can also contribute to or trigger rockfalls.
  • Quarrying (mining activities) can also play a role.

Mass Wasting: Slides

  • Slides range from extremely slow to extremely rapid and involve rocks and unconsolidated materials.
  • Rock slides: Sliding motion of rocks along a sloped surface, ranging from very slow to moderately fast.
  • Rock avalanches: Sliding motion of rocks along a sloped surface; larger rocks move quickly, breaking down into smaller pieces.

Mass Wasting: Slumps (Slides)

  • Slumps occur when layers of unconsolidated material are thick (over 10 meters) on a curved slope.
  • The mass of unconsolidated material moves gradually downward and outward.
  • Slumps can occur extremely slowly to moderately fast.
  • Excess water between the layer of unconsolidated material and the curved slope can trigger or contribute to slumps.

Mass Wasting: Flows

  • Flows range from extremely slow to extremely rapid. They are generally associated with unconsolidated materials.
  • Creep: Very slow (millimeters to centimeters per year) movement of soil/unconsolidated materials down a slope.
  • Creep can be enhanced by factors like frozen subsoil, preventing water drainage and wet material above, freeze-thaw cycles, frequent wetting/drying of soil.
  • Solifluction: Creep triggered by freeze-thaw in colder climates, where wet material or soil moves slowly through a slope.

Mass Wasting: Flows (Mudflows and Debris Flows)

  • Mudflows and debris flows involve rapid to extremely rapid movement of soil/sediment/unconsolidated materials down a slope.
  • Sediment/unconsolidated materials saturated with water lose strength and the ability to stay together.
  • The mixture of saturated materials and water turns into a flow.

Mass Wasting: Flows (Mudflows and Debris Flows cont.)

  • Mudflows involve water-saturated material whose grains are sand-sized or smaller.
  • Debris flows involve water-saturated material whose grains are gravel-sized or larger.

Mass Wasting: Topples

  • Top-piling is another form of mass wasting that involves the rotation and forward movement of rock or unconsolidated material (earth, debris) out of a slope.
  • Top-piling can be extremely slow or rapid.
  • The triggering factors for topples can include ice/snow thaw, weathering, undercutting, and fluvial erosion.
  • The result is a pile of debris at the base of the slope, known as a talus cone.

Mass Wasting: Topples (Definitions)

  • Erosion: A geological process where materials are worn away and potentially transported naturally by wind or water.
  • Undercutting: Erosion of material at the base of a cliff or steep slope.
  • Fluvial Erosion: Erosion caused by flowing water on adjacent rock or unconsolidated materials.
  • Weathering: Breaking down or dissolving rocks and minerals on Earth's surface. Erosion can transport the weathered materials away.
  • Talus Cone: A pile of debris or rock at the base of a slope, mountain, or hill.

Mass Wasting: Defining Landslides

  • A landslide is a form of mass wasting, the failure and downslope movement of rock or unconsolidated materials due to gravity.
  • Landslides involve the movement of rock or unconsolidated material (debris or earth) down a slope due to gravity.

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Lecture Notes Set 9 Mass Wasting Pt 2 PDF

Description

Explore the concepts of mass wasting and landslides in this quiz. Understand the differences between falls, slides, and flows. Delve into the factors contributing to slope failure and learn about various types of materials involved.

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