Mass Wasting (14/05/2024) PDF

14/05/2024 Mass wasting What is mass wasting? Factors promoting mass wasting Classification of mass wasting processes G.T. Valera | Geology 11 Principles o...

14/05/2024 Mass wasting What is mass wasting? Factors promoting mass wasting Classification of mass wasting processes G.T. Valera | Geology 11 Principles of Geology Mitigation measures Mass wasting G.T. Valera | Geology 11 Principles of Geology Mass wasting 1  14/05/2024 What is mass wasting? downslope movement of rock, regolith (unconsolidated material) and soil under the influence gravity some mass-wasting processes act very slowly; others occur very suddenly, often with disastrous results G.T. Valera | Geology 11 Principles of Geology Mass wasting Mass wasting Dingalan, Aurora Real, Quezon Maco, Compostela Valley G.T. Valera | Geology 11 Principles of Geology Mass wasting 2  14/05/2024 Factors promoting mass wasting 1. Slope Material resting on flat surface will not move under force of gravity On a slope, force of gravity is divided into 2 components: normal to surface and tangential to it If gt (to downslope)> gp (stay in place): mass wasting G.T. Valera | Geology 11 Principles of Geology Mass wasting Legend: Yellow – slope < 15º Black – slope > 45º G.T. Valera | Geology 11 Principles of Geology Mass wasting 3  14/05/2024 Factors promoting mass wasting 2. Water angle of repose or steepest angle at which a pile of unconsolidated grains remain stable dry, undersaturated soil, saturated soil G.T. Valera | Geology 11 Principles of Geology Mass wasting Factors promoting mass wasting 3. Soil cover Soil is more unconsolidated, and water percolating down may reach its contact with bedrock. This interface may serve as a sliding plane; Thicker soil cover, greater volume of unconsolidated material G.T. Valera | Geology 11 Principles of Geology Mass wasting 4  14/05/2024 Factors promoting mass wasting 4. Geologic features Type of rock Presence of joints or fractures Presence of bedding planes If direction of slope is the same as direction of planar features: daylighting slope G.T. Valera | Geology 11 Principles of Geology Mass wasting “Daylighting” structures G.T. Valera | Geology 11 Principles of Geology Mass wasting 5  14/05/2024 Triggers of mass wasting 1. Ground shaking (e.g.earthquake or volcanic eruptions) 2. Excessive rainfall that may saturate unconsolidated material G.T. Valera | Geology 11 Principles of Geology Mass wasting G.T. Valera | Geology 11 Principles of Geology Mass wasting 6  14/05/2024 Triggers of mass wasting February 2012 Negros Oriental Trigger: earthquake www.phivolcs.dost.gov.ph/html/update_SOEPD/ 2012_Earthquake_Bulletins/February/2012_020 6_0349_B4_files/2012_0206_0349_B4.jpg Casualties: 51 dead 62 missing 112 wounded NDRRMC G.T. Valera | Geology 11 Principles of Geology Mass wasting 1. Ground shaking (e.g.earthquake or volcanic eruptions) 2. Excessive rainfall that may saturate unconsolidated material (material is data for 150 years) G.T. Valera | Geology 11 Principles of Geology Mass wasting 7  14/05/2024 Triggers of mass wasting January 2012 Pantukan, Compostela Valley Trigger: rain Casualties: 38 dead 16 injured 37 missing NDRRMC G.T. Valera | Geology 11 Principles of Geology Mass wasting Classification of mass wasting processes Type of movement (slope failures) sudden failure of the slope resulting in transport of debris down hill fall, topple, slide, slump, spread and subsidence, flow Water content and rate of movement materials flow downhill mixed with water or air slurry flows (solifluction, debris flows, mudflows) granular flows (creep, earth flows, grain flows, debris avalanches) Type of material Rock, solid or debris G.T. Valera | Geology 11 Principles of Geology Mass wasting 8  14/05/2024 Halsema Highway Fall sudden movement of rock, separated along fractures or bedding planes no fluidity in the motion, only bouncing, rolling and free fall H. Cabria, 2002 G.T. Valera | Geology 11 Principles of Geology Mass wasting Topple Charmouth, UK blocks of material fall over as a unit, similar to falling dominos anaheim-landslide.com/types.htm Chaco Canyon, NM www.charmouth.org/html/geology/ www.science.ubc.ca/~geol351/imgset.html geology%20gallery/gallery.ht G.T. Valera | Geology 11 Principles of Geology Mass wasting 9  14/05/2024 Slides (Translational) result when rocks (rock slides) and debris (debris slides) slide down a pre-existing surface, such as a bedding plane, foliation surface, or joint La Union – Ilocos Sur, Philippines geology.about.com/od/naturalhazardsclimate/ig/Landsli des/ Mines and Geosciences Bureau G.T. Valera | Geology 11 Principles of Geology Mass wasting Ilocos Norte, Philippines Slumps (Rotational slides) downward rotation of rock or regolith occurs along a concave-upward curved surface leave arcuate scars or depressions on the hill slope Benguet, Philippines geology.about.com/od/naturalhazardsclimate/ig/Landslides/ Mines and Geosciences Bureau G.T. Valera | Geology 11 Principles of Geology Mass wasting 10  14/05/2024 Flow materials behave in a fluid manner and move rapidly El Salvador anaheim-landslide.com/types.htm www.science.ubc.ca/~geol351/imgset.html G.T. Valera | Geology 11 Principles of Geology Mass wasting Spread and subsidence Japan G.T. Valera | Geology 11 Principles of Geology Mass wasting 11  14/05/2024 Classification of mass wasting processes Type of movement (slope failures) sudden failure of the slope resulting in transport of debris down hill fall, topple, slide, slump, spread and subsidence, flow Water content and rate of movement materials flow downhill mixed with water or air slurry flows (solifluction, debris flows, mudflows) granular flows (creep, earth flows, grain flows, debris avalanches) Type of material Rock, solid or debris G.T. Valera | Geology 11 Principles of Geology Mass wasting Classification of mass wasting processes 64.19.142.13/www.tulane.edu/~sanelson/images/sedflows.gif_hyuncompressed G.T. Valera | Geology 11 Principles of Geology Mass wasting 12  14/05/2024 Creep very slow, usually continuous movement of regolith down slope anaheim-landslide.com/types.htm 0.tqn.com/d/geology/1/7/J/4/1/creeprock.jpg 0.tqn.com/d/geology/1/7/H/4/1/treecreep.jpg G.T. Valera | Geology 11 Principles of Geology Mass wasting Solifluction flowage at rates measured on the order of cm/yr of regolith containing water produces distinctive lobes on hill slopes, where the soil remains saturated with water for long periods of time solifluction lobes, Kyrgyzstan G.T. Valera | Geology 11 Principles of Geology Mass wasting 13  14/05/2024 Earth flows 1995 La Conchita landslide, USA (CA) involve fine-grained materials that form a thick slurry and have a fluid motion; usually associated with heavy rains and move at velocities between several cm/yr and 100s of m/day ooze rather than rush; form lobes rather than long streams like debris flows geology.about.com/od/naturalhazardsclimate/ig/Landslides/ G.T. Valera | Geology 11 Principles of Geology Mass wasting Debris flows occur at higher velocities than solifluction, with velocities between 1 m/yr and 100 mm/hr and often result from heavy rains causing saturation of the soil and regolith with water sometimes start with slumps and then flow down hill forming lobes with an irregular surface consisting of ridges and furrows Wooden Valley, USA (CA) 0.tqn.com/d/geology/1/7/P/X/woodenvlydebrisflow.jpg G.T. Valera | Geology 11 Principles of Geology Mass wasting 14  14/05/2024 Grain flows usually form in relatively dry material, such as a sand dune, on a steep slope a small disturbance sends the dry unconsolidated grains moving rapidly down slope 64.19.142.13/www.umt.edu/geosciences/faculty/hendrix/g432/g43 2_L10_files/Image121.jpe_hyuncompressed 64.19.142.13/www.umt.edu/geosciences/faculty/hendrix/g432/g432_L10_files/Image12 0.jpe_hyuncompressed G.T. Valera | Geology 11 Principles of Geology Mass wasting Mudflows highly fluid, high velocity mixture of sediment and water that has a consistency ranging between soup-like and wet concrete move at velocities greater than 1 km/hr and tend to travel along valley floors February 2006 Southern Leyte Trigger: prolonged rainfall (La Niña weather) Death toll: ~1,126 people www.defense.gov/home/features/Leyte/landslide/images/hi-res/060219-N-5067K- 109.jpg G.T. Valera | Geology 11 Principles of Geology Mass wasting 15  14/05/2024 December 2006 Mt. Mayon mudflows Trigger: heavy rainfall (TY Reming | Int: Durian) www.fotothing.com/photos/3d1/3d100a5b7a97a4f42298708405cd6df9.jpg G.T. Valera | Geology 11 Principles of Geology Mass wasting December 2006 Mt. Mayon mudflows Trigger: heavy rainfall (TY Reming | Int: Durian) earthobservatory.nasa.gov Death toll: ~1,266 people ++ G.T. Valera | Geology 11 Principles of Geology Mass wasting 16  14/05/2024 Goodell Creek, USA (WA) Debris avalanches very high velocity flows of large volume mixtures of rock and regolith that result from complete collapse of a mountainous slope often triggered by earthquakes and 64.19.142.11/upload.wikimedia.org/wikipedia/commons/thumb/3 volcanic eruptions /3e/Goodell_Creek_Debris_Avalanche.jpg/800px- Goodell_Creek_Debris_Avalanche.jpg Mt. St. Helens, USA (WA) https://giphy.com/gifs/landslide-h4R3CamOsE8Sc 0.tqn.com/d/geology/1/7/k/-/1/slide-debalanche.jpg G.T. Valera | Geology 11 Principles of Geology Mass wasting Mitigation measures Hazard maps provide information about proper land use in certain areas identified to be prone to mass wasting “hard” engineering measures (e.g. construction of features to stabilize slope) or “soft” measure (e.g. monitoring) G.T. Valera | Geology 11 Principles of Geology Mass wasting 17  14/05/2024 G.T. Valera | Geology 11 Principles of Geology Mass wasting Engineering measures Retaining wall Concrete cover Chicken wire Coconet G.T. Valera | Geology 11 Principles of Geology Mass wasting 18  14/05/2024 Engineering measures Weep holes Benching Rock barriers G.T. Valera | Geology 11 Principles of Geology Mass wasting What areas should you avoid? Areas That Are Generally Prone To Landslides On existing landslides, old or recent On or at the base or top of slopes In or at the base of minor drainage hollows At the base or top of a steep cut slope G.T. Valera | Geology 11 Principles of Geology Mass wasting 19  14/05/2024 “Soft” measures Information and education campaign Monitoring (e.g. slopes, rainfall conditions etc.) Early warning system Hazard preparedness program Rehabilitation/coping mechanism program G.T. Valera | Geology 11 Principles of Geology Mass wasting 20