Mass Movement
Mass Movement is any one of several processes
that move sediment downhill. The different types
of mass movement include landslides, mudflows,
slump, and creep. Gravity is the number one cause
of mass movement. Mass movements can vary from
being rapid or super slow it all depends on the type.
Landslides
Landslides are the most destructive type of mass movement. Landslides occur when rock and soil slide quickly down a steep slope. Landslides can contain Huge masses of rock, soil, and smaller sediment. Most landslides occur where roads have cut through hills or mountain ranges.
Mudflows
Mudflows can be very dangerous.
Mudflows are a mixture of water,
rock, and soil rapidly flowing downhill.
Mudflows usually occur after a heavy
rain in a normaly dry place. Mudflows
can contain as high as 60 percent of
water. Sometimes when soil has lots
of clay with a high water content,
mudflows can occur even on a very
gentle slope, under certain conditions
clay soils turn into liquid making it
easier to flow downhill.
Slump
A slump is when a mass of rock and soil attached to an even bigger mass of rock and soil suddenly slip down a slope. A slump occurs when water soaks the bottom of a slope and erodes it until that part of the slope finally collapses. A slump is different than a landslide because unlike the landslide a slump all moves down the slope at the same time in one huge mass.
Creep
Creep, in geology, slow down slope movement of particles that occurs on every slope covered with loose, weathered material. Even soil covered with close-knit sod creeps down slope, as indicated by slow but persistent tilting of trees, poles, gravestones, and other objects set into the ground on hillsides. The most important process producing creep, aside from direct gravitational influences, is frost heaving: as interstitial water freezes, surface particles are forced up and out perpendicular to the slope; when let down by melting, these particles are drawn directly downward by gravity and are thereby gradually moved down slope. Other processes involved are the wedging action of root growth and the wetting and drying of soil layers.
Mass Movement PPT
https://www.wsfcs.k12.nc.us/cms/lib/NC01001395/Centricity/Domain/1190/Chapter%2008.pdf
-------------------------------------------------------------------------------------------------------------------------------------------Mass Movement Webquest help
Weather is the process of breaking rocks into sediment while erosion is the process that wears away this sediment and other materials and moves them from one location to another. Agents of erosion include gravity, glaciers, wind, and water. Erosion only occurs when these agents have enough energy. The moment agents of erosion lose their energy and momentum they deposit their load. This process is known as deposition. The load is what the agent is carrying. As agents of weather lose their energy they the heavier sediment begins to be dropped.
Mass movement, sometimes referred to as mass wasting, is what we call the movement of surface material due to gravity, water, wind, and ice. There are four main types of mass movements: creep, flows, slides, and slump.
Slump occurs when soil and rock slip down slope in one large mass. It happens when water penetrates the upper layers of a land mass, but doesn't penetrate the lower layers causing the ground to move outward and on top of the lower layers. Evidence of slump having happened is upturned curved scars in the side of a hill or bank of a river. Earthquakes can also cause slump as the ground is shaken, the top layers can fall and slide out overtop of the bottom layers. Below are some images demonstrating slump.
Creep happens when sediments slowly move downhill. This one is easy to remember because the sediment creeps downhill. You can tell creep is happening when you see power lines, trees, fences, ending up curved or tilted.
When rock falls, crumbles, or rolls quickly downhill we call it a slide, commonly called landslides. This type of mass movement happens in mountainous areas are where the Earth contains steep cliffs. You can easily tell that a landslide has happened when you see rocks and other sediment gathering at the base of a slope or mountain. This pile of rock, at the base of a slope is called talus.
Flows are the most devastating type mass movement. Imagine a thick wall of mud, rock and debris coming toward you at high speeds, moving like a river of water, except in this case swimming would be nearly impossible. Flows happen due to an accumulation of weathered material in dry areas. Piles of debris and sediment is present. When a rain happens in this area, with all of this material; because it is loose the water has an easy time penetrating it, and then gravity forces all of this sediment down hill where it picks up other sediment on its way. Evidence: When the wash up debris hits the base of the slope it spreads out in a conical shape called an alluvial fan. A special type of mudflow is a lahar. A lahar happens when a volcano begins to heat up it snow filled slopes and melts the ice and snow. This causes very quick and dangerous mudflows that can travel many miles destroying anything in its path.
Section 2 Daily Dose of Destruction
Mass movement or mass wasting happens after the angle of repose has been breached. The angle of repose is the steepest angle at which a sloping surface made out of a specific material is stable. The moment the angle of a slope has become too steep, due to circumstances like undercutting and erosion, the slope with that material will collapse until it is stable once more. Once a material like sand has hit the angle of repose, a mass movement event is inevitable. All it will take is a slightly steeper angle and then BOOM, the slope collapses. Adding a solvent like water can change the angle of repose as well. Below is a video experimenting with two types of sand to demonstrate that the angle of repose is different based on the material types.
Most costly landslide in US:
Thistle, UT
https://www.ngdc.noaa.gov/hazardimages/picture/show/1548
Most deadly landslide in US:
Mudslide in Oso, Washington that killed 43 people
https://www.huffingtonpost.com/2015/03/22/oso-washington-mudslide_n_6918178.html