GLY1000 Exam 3 Study Guide Mass Wasting Mass Wasting is the down slope hill movement of rock soil or sediment under the influence of gravity Understand all the factors that effect mass wasting i e what factors influence the stabilities of slopes and how they effect it o Nature of the materials o Steepness of slope Gravity provides the energy to move the materials Rapid movements e g landslide slumping are commonly found on steep slopes while slow movements e g soil creep are found on gentle slopes o Water Rainwater acts as a lubricant to weathered materials Rainwater adds weight to weathered materials o Vegetation Lack of vegetation cover to hold the loose particles o Presence and orientation of planes of weakness Joints dipping usually assists landslides rock falls rockslide rock creep etc o Heights Steeper the slope the more likely it is to fail o Climate Areas with a moist temperature climate are subjected to frequent freeze and thaw cycles freeze thaw cycles affect tocks because when water seeps into cracks in a rock then freezes it expands putting tremendous pressure on the rock forcing cracks to expand o Vibrations Earthquakes Construction processes and mining operations Think about some ways in which human activity can influence these factors and what the results of such activity might be o Drainage diversion and irrigation projects destabilize slopes and increase the probability of mass wasting by increasing the moisture in vulnerable areas o Blasting associated with mining o Transportation vibration increasing the load that the ground must bear changing vegetative cover and pumping Some natural processes that over steepen slopes include o Stream erosion the loosening and transportation of soil and rock from one location to another by streams and rivers GLY1000 Exam 3 Study Guide o Wave erosion The pure energy of waves along with the chemical content of the water is what erodes the rock of the coastline o Tectonic uplift the portion of the total geologic uplift of the mean Earth surface that is not attributable to an Isostatic response to unloading o Volcanic activity can cause debris avalanches Mass wasting events are manifested in different ways and at different rates depending on the types of materials involved such as rock earth mud debris and the type of motion involved such as fall slide flow To what do the terms creep slump and avalanche refer what about the rates at which they occur o Creep cm year or less o Slump Rapid Movement o Avalanche Rapid 160 km hr Landslide is general term referring to all slides flows even falls that occur at a moderately fast rate o They occur on steep slope Gravity provides the energy to move materials so the force of downhill pull is greater on steep slope o Types of landslides Slide Movement of rock materials downslope along a slide plane Slump occurs along a curved slide plane Be familiar with the details of creep and the structure geometry and behavior of slumps o Creep occurs at the slowest rate of mass wasting processes often at a cm year or less The slow downhill movement of ground surface by creep destroys the foundations of buildings highways railways underground pipelines and utilities o Slumps In slumps material moves as coherent mass along the curved surfaces This motion results in a slightly backward rotation of blocks The distal end toe of the slump moves along a less steep surface Often the toe of slumps moves more as flows than as slides GLY1000 Exam 3 Study Guide How can you recognize evidence of past mass wasting events o Look for signs that they have occurred Scars and debris piles reveal former landslides Scarps displaced objects and hummocky terrain betray creep What if anything can be done to lessen the possibility of future such events in areas prone to mass wasting o Many potential human activity related problems can be avoided by using good land use planning techniques and engineering solutions where appropriate o Avoidance of development in areas prone to rock falls and landslides o Proper maintenance and inspection of mass wasting prone areas is essential to spotting potential hazards Streams Recall that precipitation that does not evaporate either infiltrates the ground or runs off the surface Remember what factors affect the infiltration capacity of the ground Runoff is either in the form of sheet flow such as during floods or it is confined to channels Channelized runoff is stream flow o Factors that influence the infiltration versus runoff include The permeability of the surficial material The slope of the land Amount and type of vegetation Recent amounts of precipitation degree of saturation of the land Things that reduce the infiltration capacity of the ground results in more runoff and greater flooding potential Think of some natural and human activities that can increase the flooding potential of streams o Human development clearing of land alters the characteristics of the ground cover and clears land of its natural vegetation vegetation works with the soil to store rainfall so when vegetation is cleared the rainfall runoff can increase substantially o Construction of roads and buildings also acts to increase runoff and leads to an increasing in flooding o Streams erode the surface of the Earth picking up sediments they transport sediments and they deposit sediments There are erosional landforms produced by steams and there are depositional landforms produced by streams what are some o Erosional landform channel canyon valley o Depositional landforms floodplain meander oxbow lake delta alluvial fan GLY1000 Exam 3 Study Guide What factors affect the velocity of streams Understand how and why these factors effect velocity o Stream gradient slope of surface over which it flows When a river flows down a steep slope the gravitational force that pulls the water downward is stronger than it would be on water flowing down a gentle slope resulting in the river having a greater level of velocity o The size and shape of the channel Water flowing through a wide deep river channel encounters less resistance higher velocity than water flowing in a narrow shallow channel lower velocity since a smaller proportion of the total water molecules will be slowed by the river s edges The center of the river experiences the greatest velocity o Channel roughness Rougher the water the less velocity smooth river channel high velocity o Discharge the amount of water flowing pass a point on a stream per unit time more water
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