Rockfalls occur when rock fragments fall from steep cliffs. This is the fastest type of mass movement. The fragments may be as tiny as pebbles or as huge as giant boulders. Landslides occur when large amounts of loose rock combined with soil fall suddenly down a slope.
Which is an example of mass movement? Types and Examples of Mass Movement Flows include mudflows, debris flows or lahars superheated water that moves down an erupting volcano. Which landslide type moves the fastest? Which types of mass movement are most dangerous to humans? Landslides and avalanches are the most dramatic, sudden, and dangerous examples of earth materials moved by gravity.
Landslides are sudden falls of rock, whereas avalanches are sudden falls of snow. Here is a video of a snow avalanche. What kind of mass movement happens continuously? Creep - the very slow, usually continuous movement of regolith down slope. Creep occurs on almost all slopes, but the rates vary. Evidence for creep is often seen in bent trees, offsets in roads and fences, and inclined utility poles. How many types of mass are there?
What's the difference between the five masses: inertial mass, gravitational mass, rest mass, invariant mass and relativistic mass? I have learned in my physics classes about five different types of masses and I am confused about the differences between them. How are mass movements classified?
Types of mass movement there is. Types of landslides. These illustrations presented by the USGS show typical landscape features associated with landsliding. Avalanches are common mountainous country. The Hazel Landslide of near Arlington, Washington formed where a river undercut a slope of unconsolidated sediments.
A debris flow deposit caused by a debris flood in Santa Barbara, CA in Helens associated with an eruption in August, A lahar on Mount St. Helens that occurred in Mount Shasta in northern California the most massive volcano in the Cascade Range displays evidence of massive prehistoric landsliding. The summit of Mount Rainier shows evidence of massive landsliding. Much of Tacoma Washington and other surrounding cities are built on the lahar deposits from the volcano. Wildfire is a major force of destruction, but can also generate vast quantities of sediment as ash, dust, and debris.
These boulders on Bernardo Mountain in San Diego County display evidence that fire scorching can help break down rocks. This fire-scorched landscape on Double Peak, San Marcos California, show that even the soil organic content is burned in a fire.
A debris flow from a fire-burned landscape wiped out a campground in Cable Canyon, California in Chapter 9 - Weathering, Erosion, and Mass Wasting. The rocky surface of the planet is subjected to processes that break down rocks and move materials. This chapter focuses focuses on the weathering and erosion of rocks to form sediments, and the transport and modification of sediments to sites of deposition. Weathering and erosion impact the surface of the land in many way. Much of this relates to the mechanical, chemical, and biological processes breaking down rocks while shaping the landscape, including the formation of soils.
Gravity has a large role in moving material downhill in a variety of means called mass wasting. Mass wasting is associated with a variety of serious landslide hazards that are often associated with heavy precipitation.
Landslides can take place slowly or rapidly, and intermittently such as events associated with seasonal storm floods or some that are triggered by earthquakes or human activities.
What Are Weathering and Erosion? Rocks exposed on or near the surface are exposed to physical and chemical interactions with air and water, and changes in temperature and pressure.
Weathering is the mechanical and chemical disintegration of rock on th surface of the Earth. Weathering produces sediments, erosion moves sediments. Weathered materials are subjected to gravitation forces pulling them downhill and are transported by forces of erosion associated with flowing water, ice, or wind. Erosion involves processes that wears down and removes materials exposed on the surface.
This includes materials exposed on the land, below the oceans, or under glaciers. Sediments are solid fragments of inorganic or organic material that come from the weathering and erosion of rock. Soil is made up of sediments and organic matter, and forms from the processes associated with weathering and erosion. Sediments can be eroded , transported , and deposited. Deposition is the process of sediments settling and accumulating from a moving fluid wind, water, or ice.
Once sediments have accumulated in a stable setting they can gradually undergo compaction and cementation to form sedimentary rocks. Sedimentary processes and the sediments and rocks they produce are part of the rock cycle Figure This chapter focuses on weathering and the production and movement of sediments.
Deposition and formation of sedimentary rocks are discussed in the next chapter on Sedimentary Rocks. Click on images for a larger view throughout this website. Sediments , sedimentary rocks and sedimentary processes are part of the rock cycle. Weathering Weathering is the gradual destruction of rock under surface conditions. Weathering may involve physical processes called mechanical weathering or chemical activity called chemical weathering.
Biological activity can also result in weathering that can be construed as mechanical, chemical, or both. Weathering processes can begin long before rocks are exposed at the surface. This is true in most places on the earth surface where rocky outcrops bedrock is not exposed.
In addition, weathering and erosion can take place simultaneously, perhaps most obviously in settings like rivers in flood, or waves crashing on a beach. Mechanical weathering is any process that makes big pieces into smaller fragments. Glaciers moving ice scours bedrock and produce and carry away large quantities of sediment. Weathering of Rocks Produces Sediments Sediments are solid fragments of inorganic or organic material that come from the weathering of rock and soil erosion, and are carried and deposited by wind, water, or ice.
Sediments can be eroded and deposited. Erosion involves the mechanical processes of wearing or grinding away materials on a landscape by the action of wind, flowing water, or glacial ice under the influence of gravity. Deposition involves the processes of sediments settling and accumulating from a moving fluid wind, water, or ice. Most deposits of sediments preserve evidence about how, when, and why they were deposited!
Gravity drives mass wasting. In this case, a rock fall, breaks big pieces into fragments. Flood waters can move all sizes of sediments, when the water slows down, sediments are deposited. Mechanical Weathering Mechanical weathering involves all processes that collectively break rocks into smaller pieces see examples in Figures to Mechanical weathering includes all forms of mass wasting —a general name for processes by which soil and rock move downslope under the force of gravity.
Mass wasting , a form of mechanical weathering, includes sudden events such as rock falls , landslides and avalanches —to long-lasting processes including slow movements of massive slumps or the slow creep of material down hillsides. These processes break "big pieces of rocks into smaller pieces.
Mechanical weathering can involve erosional grinding as fast-moving flood waters moves boulders and sediments down stream valleys and where wave action batters rocks into sand along a shoreline. Rocks are shattered by earthquakes and volcanic explosions, the expand and split when erosion unloads overburden on compressed rocks that were previously deeply buried.
Rocks will split when water freezes and expands in cracks. Rocks exposed on the surface are subject to expansion and contraction caused by daily heating and cooling particularly effective in arid environments.
Mechanical weathering is also caused by organic activity—the breakdown and movement of rock and soil caused by expanding tree roots, burrowing, feeding activity, etc. The mechanical breakdown of rocks increases the surface area per unit area increasing the available surface area where chemical weathering can take place see Figure Mechanical weathering involves all processes that collectively break rocks into smaller pieces.
Examples include breaking rocks by water expansion during freezing in cracks, plant root expansion, all forms of mass wasting, and rock particles breaking as they tumble down hillsides and stream beds during floods or get battered by wave action along a shoreline. Examples of mechanical weathering processes include: Erosional grinding —the physical banging and cracking of rock as it is moved by water, wind, or ice, such as waves crashing on a sea cliff, boulders and gravel carried in a fast moving stream, or grinding of rock materials along the bottom of a moving glacier.
Frost wedging —the shattering, fracturing, and moving rock and soil caused by the expansion of freezing water turning into ice. Frost wedging is a major force in seasonally wet regions where daytime temperatures rise above freezing and sink below freezing at night.
Unloading —expansion of compressed rocks previously deeply buried by the removal of overburden, allowing rocks to expand and fracture, commonly resulting in the sheeting off of layers of rocks.
Exfoliation— joints or sheet joints are surface-parallel fracture systems in rock often leading to erosion of concentric slabs. Thermal expansion —expansion and contraction caused by daily heating and cooling, particularly effective in arid environments. Heat from wildfires can also cause thermal expansion and break down rocks by driving out steam and gases trapped in rocks and soil. Biological activity —breakdown and movement of rock and soil caused by expanding tree roots, burrowing, feeding activity, etc.
Frost wedging ice expands when it freezes helps to sculpt unusual landscapes, such as these hoodoos at Bryce Canyon National Park in Utah. Volcanic eruptions produce large volumes of ash and other debris that accumulate and can be eroded, transported, and deposited as sediments.
Flowing water transports, grinds fragments, and erodes landscapes. Stream and river erosion are dominant forces changing mountainous landscapes. They contribute most of the sediments that build beaches and shoreline deposits.
Wave action along shorelines grinds rocks into fragments. Storm-driven currents in ocean and lake settings and wave action along coastlines can move tremendous amounts of sediments. The breakdown of sediments by mechanical and chemical weathering continues into the deep ocean basins of the world.
The deep ocean is where most sediment eventually end up, only to be recycled again! The mechanical breakdown of rocks increases surface area per unit volume. Increased surface area increases the space for chemical weathering processes to take place. Chemical Weathering Chemical weathering involves the breakdown decomposition, decay, and dissolution of rock by chemical means. Water is the most important agent of chemical weathering.
Dissolution is the action or process of dissolving or being dissolved, moving soluble components of materials into solution. Leaching is the process of dissolving and removing the soluble constituents of soil or rock near the land's surface.
Water flowing under the influence of gravity carries dissolved materials away, ultimately adding to the saltiness of the oceans or they are deposited as salts, such a such as in an inland desert basin.
In most surface and near surface settings, mechanical and chemical weathering are taking place simultaneously Figure Weathering is enhanced in environments where repeated wetting and drying periods take place.
The chemical breakdown of rocks is most rapid where warm and humid climatic conditions persist. Mechanical weathering processes dominate in cold settings where daily heating and cooling, and freezing and thawing cycles occur frequently in winter months. Forest fires can have similar heating and cooling effects on breaking rocks on the surface. Chemical weathering is enhanced along fractures in the bedrock where water, air, and organic acids seep through.
Rusting old cars illustrate the same chemical weathering process that break down rocks. Most rust is a natural iron-hydroxide mineral called limonite! The process of making tea or coffee is a good illustration of weathering processes. Hot water poured into coffee grounds or tea bags will dissolve and leach soluble components but will leave behind the insoluble components. Chemical Reactions Involved In Weathering Chemical weathering involves a variety of chemical reactions including hydrolysis, hydration, oxidation, and carbonation.
A mineral that is exposed to air may undergo oxidation. Decaying organic matter releases carbonation and organic acids that enhance the chemical reactivity between rocks and groundwater. All these chemical processes are happening around us. Weathering and erosion are continuous processes in the surface environment, enhanced by the presence of water the "universal solvent".
In addition, barometric changes in air pressure with passing storm fronts push in or pull out air from the ground. Different Minerals Weather In Different Ways Minerals that form under high temperatures or high pressures may not be stable in the surface environment.
Of the common rock-forming minerals, quartz is highly resistant to weathering processes and therefore is perhaps the most stable in the surface environment because is both hard and relatively insoluble in surface waters. Of the common minerals, quartz is most resistant to weathering on the surface. In contrast, mafic minerals and feldspars have metallic elemental components including elements Na, Ca, K, and Fe.
Under the right chemical conditions these elements can easily dissolve in water or react with oxygen, carbon dioxide, or water to form minerals that are more stable in the surface environment. The feldspars, micas, and mafic silicate minerals ultimately break down to form clay minerals. Iron that does not dissolve will hydrate or oxidize, essentially become brown-colored minerals in soil limonite and hematite.
Rust that forms on an old car is mostly the natural mineral limonite Figure Figure illustrates the fate of some of the common rock forming minerals as the break down through weathering processes. Minerals will break down into insoluble or insoluble components. Common Rock-Forming Minerals. What happens to common igneous rocks granite and basalt when they weather? Granite is common in mountainous regions in many regions in the western United States.
When granite weathers, it separates into components. Mechanical weathering forces split the rock into fragments, and the interactions of water and gases slowly chemically alter some of the minerals into clay. The quartz in granite is most resistant to weathering, and remains virtually unchanged, becoming mostly gravel , sand , and silt. In contrast, the feldspars and micas eventually break down to become clays.
Mafic minerals in granite break down into clays and iron-oxide residues hematite and limonite. Soluble components dissolve and are carried away by groundwater or surface waters, eventually contributing to the salts in seawater. Basalt and most volcanic rocks of mafic and intermediate composition experiences a different fate than granite.
Because basalt and these volcanic rocks are dominated by fine grained mafic minerals and feldspars, both of which break down to become clays. Sediments deposited along streams valleys and sediments deposited offshore of volcanic regions are generally dominated by mud iron mineral residues, silt, and clay and dissolved fractions contribute salts to seawater.
In a uniform volume of sediment, the smaller the particle size, the greater the amount of surface area compare surface area of gravel, sand and silt; see Figure The availability of oxygen controls the stability and solubility of minerals; metal oxides precipitate in oxidizing conditions; reducing environments tend to be acidic.
Silica dissolves in basic water and precipitates in acidic water. Oxidation states of iron is the source of most color in rocks and sediments. Factors That Influence Weathering Moisture —water is the universal solvent - the availability of water is a major factor in weathering of surface materials. Surface temperature —the higher the temperature, the faster chemical reactions affecting soil formation takes place. Mineral makeup —mineral compounds have a wide spectrum of solubility, oxidation-reduction, and acid-base stability and reaction rates.
Particle size —large particles have logarithmic scale increases in surface area at materials are broken into smaller and smaller sizes. Time —the longer materials are exposed to a weathering condition, the more it will decay into its weathering components. Weathering In the Subsurface, and the Origin of Rounded Boulders On the Landscape Rounded boulders are often seen on landscapes in arid regions this is particularly well illustrated in the mountainous landscapes in Southern California.
Boulders, or piles of boulders, on the landscape accumulate where chemical weathering has selectively broken down materials in the vicinity of fractures or around materials that are more durable and can withstand rock-water-air chemical weathering reactions Figure Rock falls, slumps, and debris flows are all examples of mass wasting.
Often lubricated by rainfall or agitated by seismic activity, these events may occur very rapidly and move as a flow. Landslide triggers may include:. The runout of a mass wasting event depends on the volume of material, water content, and slope steepness. A Debris Flow is a type of landslide made up of a mixture of water-saturated rock debris and soil with a consistency similar to wet cement. Debris flows move rapidly downslope under the influence of gravity. Sometimes referred to as earth flows or mud flows.
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