Intro to Geomorphology (Geos 450/550) Lecture 2: World-wind tour of the hillslope, fluvial, fan, and playa system conversion of rock to regolith diffusion equation for evol. of soil-mantled slopes detachment-limited vs. transport-limited channels cycles of cutting and filling on fans and relationship to climatic changes desert pavements and wind erosion from playas more on field trip #1 Reading: ch. 2 of Pelletier book

Geomorphic Systems: Hillslope: slope wash, bioturbation, mass movements Fluvial: water action; channels, fans, deltas Aeolian: wind action; dunes, yardangs Glacial: ice action, both alpine and ice sheet; cirques, glacial lakes Periglacial: freeze-thaw; patterned ground, thaw lakes Coastal: wave and longshore currents; spits, barrier is.

Upland landscapes are comprised of two interacting surfaces: P, rate of bedrock recession by conversion to soil, is controlled primarily by rock type, climate, soil thickness E, erosion rate is also controlled by soil thickness and topographic shape

slope profile evolution by diffusion erosion convex upwards curvature concave upwards curvature deposition Applied to dated fault scarps

Soil production function

Simplest model: Colluvial transport proportional to slope (i.e. topography is diffusive if soil exists). Bedrock recession rate decreases exponentially with soil thickness. Model predictions for soil-thickness steady state: h 0 approx. 0.5 m from cosmogenic nuclide studies predicts bare slope above a threshold concavity. breaks down for concave slopes

predicts bare slope above a threshold concavity.

Pelletier et al., 2011

Drainage density high low

T. Hughes,1987

Paleoveg in SW

Pelletier (2014)

time

Sea level changes due to ice storage

More people die on dusty days (Thorax, 2013)