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 primarilyby 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 diffusiveif soil exists).• Bedrock recession rate decreases exponentially with soil thickness.

Model predictionsfor soil-thicknesssteady state:

h0 approx. 0.5 mfrom cosmogenicnuclide 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

time

Sea level changes due to ice storage

More people die on dusty days(Thorax, 2013)