Upload
geoffrey-lang
View
217
Download
4
Embed Size (px)
Citation preview
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)