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the relentless process that transports Earth material down slopes from high to low elevation by the pull of gravity
- occurs when factors that resist movement of the load are overcome by factors driving materials downslope
- friction, gravity, cohesiveness of material |
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- Poor sorting - variety of grain sizes
- Well sorted - all uniform size, usually small as bigger chunks will get sorted out
- Breccia - conglomerate with angular clasts, often water transport
- Muddy conglomerates - mudflows, debris flows |
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| general term for mass movement deposits, any deposits created by mass movement (alluvium - put down by running water or stream) |
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| angular debris formed by roof collapse in cave |
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| angular debris at angle of REPOSE (steepest angle at which sediment can sit) at base of cliff or steep slope |
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EXCEEDING THRESHOLDS - shear stress > shear strength
1. earthquakes (cause spikes in shear stress through shockwaves)
2. layers dipping towards valley bottom (ready-made planes for slipping)
3. heavy rain/snow melt (adds weight to land surface - shear stress, can reduce shear strength of material)
4. volcanic ash & water (pasty mud - very little strength, often deposited on very steep slopes near volcano, likely to create mudslides) |
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| very slow downhill movement - often disturbs plant growth on surface (bent tree trunks) as soil moves downhill - can create waves in roads, permafrost top layer (active layer) thaws in summer, turns into soupy mess because water can't go beneath permafrost layer, creates dip in surface |
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| uphill expansion of earth and soil above creep |
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