Mass Wasting and Slope Stability Jeff Clark Lawrence

Mass Wasting and Slope Stability Jeff Clark Lawrence University

Course Details • Physics of the Earth: Surficial Environments – Physical and chemical processes that shape Earth’s surface • Focus on a few in depth • Lecture and lab coupled • Moving to integrate “field technology” • Required 300 level course (prereqs) • ~ 9 2/3 weeks (8 -9 3 -hr* labs) • 6 -10 students

Lab Context • Third and fourth labs of term – depth • Follows basic mapping and soils labs • Lectures on mechanical weathering, slope stability, and mass wasting concurrent. • All labs are group labs • First “formal” lab write up

Goals of Lab • Reinforce and build upon concepts/skills – Soils from previous labs and lectures – Mass wasting and slope stability – Strat columns • New field and lab techniques – In situ strength estimates – Morphometric indices – Aerial rephotography – Sediment size analysis – fine fraction

Goals of Lab • Scientific Habits of Mind – Sound observations to support inferences – Synthesis of multiple observations/data sets – Effective communication • Written report with tables, figures, methods, results, discussion, etc. • Other labs have oral or poster style communication forms

Lab Activities • Create stratigraphic column – Measurements, sampling, and observations • Measure slide morphometry – Use survey skills and identify slide features • Map present shoreline and cliff – Relate to historic shoreline position

Top 5 m of strat column • Describe color, texture • Measure strength • Sample From Geo. Test

In-situ measures of strength

Mophometric Index D/L Crozier, 1973; reprinted in Ritter, Kotchel and Miller, 2002

Mophometric Index D/L Crozier, 1973; reprinted in Ritter, Kotchel and Miller, 2002

Mapping and Rephotography

Second Week • Determine rates of retreat – GIS • Hydrometer analysis – Correlate with strength • Moisture content? • Revisit site? • Compile report

Why does this lab “work” • Multiple clear “textbook” possibilities for failure mechanism – Wave-cut toe, profoundly weak layer, pore water, historic changes in lake level • Several Possible interpretations • Requires synthesis of different types of observations/measurements

Problems • Reports – students need guidance on structure and content – Use background reading article as model? • Data sharing is problematic – Try electronic field forms/notebooks • Students tend to wait until the second week to work on project – Build in credit bearing check points • Too ambitious even for groups – May remove GPS mapping in future