CEE 1030 1nd Edition Lecture 15 Mass Wasting Outline of Last Lecture I Mapping the ocean floor II Types of continental margin III Types of plate boundaries IV Isotasy and crustal thickness V Origin and evolution of continents Outline of Current Lecture I Mass wasting a Role of particle size and shape b Role of water c Role of underlying surface II Other factors of mass wasting III Review IV Mass wasting processes Current Lecture I Mass wasting a Mass wasting the movement of rock regolith and or soil downslope under direct influence of gravity i Regolith gathering of rocks on Earth s surface b Landform development i Weathering weakens and breaks rock apart ii Mass wasting transfers debris downslope via gravity c Stable and unstable slopes i When loose sediments are piled particles move downslope until pile s slope becomes stable ii Sediment piled too steeply unstable d Angle of repose the steepest angle at which a pile of unconsolidated sediment remains stable i Varies according to 1 Size and angularity of sediment particles a Larger particles have smaller angle of repose b Rounded particles have smaller angle of repose c Think of marbles vs sand marbles vs pennies These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III IV 2 How much water is mixed in a Dry particles angle of repose determined by friction of grain to grain contact b Small amount of water increases angle of repose c Large amount of water decreases angle of repose eliminates particle cohesion 3 Friction of surface beneath the pile a Angle of repose is affected by the friction of particles against surface beneath the sediment pile i Low friction surface smaller angle of repose ii High friction surface greater angle of repose b Think of slippery snow vs frozen dirt Other factors of mass wasting a Oversteepened slope landscape with slope greater than material s angle of repose unstable b Effects of vegetation removal i Deforestation increases rate of mass wasting by decreasing angle of repose ii Root systems bind soil and regolith together c Stabilizing an unstable slope i To stabilize insert something that will increase the angle of repose ii Add reinforced terraces iii Establish native plants with deeper root systems d Earthquakes as triggers i Ground vibrations from earthquakes can cause liquefaction when shaken water saturated surface sediments can act as a fluid and flow e Submarine landslides i Mass wasting is common and widespread on the ocean floor ii Landslides often occur along passive continental margins and flanks of submarine volcanoes Review a Primary force controlling mass wasting gravity b What would increase the angle of repose Flatter particles Mass wasting processes a Basis of classification i Type of material 1 Rock debris earth by decreasing size ii Movement 1 Fall free fall of sediment 2 Slide sediment moves along surfaces 3 Flow material moves as viscous fluid iii Velocity 1 Most rapid events occur in areas of rugged geologically young mountains b Types of slides i Translational slide material moves down a slope along flat surface ii Rotational slide slump material moves downslope along a curved rupture surface c Types of flows i Creep slow movement ii Flow fast movement iii Avalanche very fast movement iv Solifluction a type of creep in which water saturated soils flow slowly downhill typically in areas where water cannot escape from the saturated surface layer by infiltrating to deeper layers
View Full Document
Unlocking...