Humboldt State
University Department of Geology
Because of copyright restrictions, these slide and overhead
transparency files are password protected and limited to use by
students enrolled in Geology classes at Humboldt State University
Lecture Slides: Weathering and
Soils
Physical Weathering
Exfoliation -- jointing caused by pressure release due to
erosion of overlying rock
- Exfoliation
diagram -- diagram showing weathering due to pressure
release
- Exfoliation
-- jointing due to pressure release, North Cascades Highway,
Washington
- Exfoliation
-- onion-skin jointing due to pressure release, Yosemite National
Park, CA
- Exfoliation
-- pressure-release jointing subparallel to canyon walls, North
Creek, NY
Frost wedging or riving -- due to expansion of water on
freezing
Spheroidal weathering -- due to corners and edges of joint
blocks weathering more rapidly than faces
Salt crystallization (cavernous weathering) -- due to growth of
salt crystals in rock pores and cracks
Granular disintegration (grusification) -- due to expansion of
biotite grains on slight chemical weathering
- Granular
disintegration of granite cobble in 10,000 year old glacial
till -- near Sumas, Washington
- Granular
disintegration of biotite -rich diorite -- can be dug apart
with a knife! Medford, Massachusetts
- Residual
granite blocks exposed in in roadcut -- Sierra Nevada, CA
- Granite
tor -- formed by erosion of weathered (grusified) granite,
Pikes Peak, Colorado
- Granite
residual boulders -- typical weathering of granite, near
Bishop, CA
- Weathered
granite outcrops -- typical weathering of granite, Mojave
Desert, CA
- Hills
of weathered granite -- typical weathering of granite,
Sudan
Expansion and shrinking of clays on wetting and drying
Other mechanisms
Chemical Weathering
Solution
- Solution
rills in limestone -- Nevada
- Joints
and small pits enlarged by solution -- Inishmore, Ireland
- Joints
enlarged by solution -- Inishmore, Ireland
- Cave
formation diagram
- Limestone
cave -- Carlsbad Caverns, New Mexico
- Karst
features diagram -- diagram showing features of a
solution-dominated (karst) landscape
- Disappearing
stream -- karst topography: stream disappearing into
sinkhole
- Sinkholes
above caves -- Colorado
- Sinkhole
-- sacred well of Chichen Itza, Mexico: a large sinkhole in
limestone
- Winters
Park sinkhole -- this sinkhole swallowed up a car dealership
in 1981. Winters Park, Florida
- Karst
topography -- sinkholes near Bowling Green, Kentucky
- Karst
topography -- cone karst near Arecibo, Puerto Rico
- Karst
topography -- tower karst, Guilin, China
- Karst
topography -- tower karst, near Guilin, China
- Karst
topography -- topographic map showing solutional
topography
Soils and Soil Formation
- Soil
horizons -- general diagram
- Soil
profile -- a more realistic diagram
- Thin
young soil on exfoliated granite -- Lynches River, South
Carolina
- Deeply
weathered granite (saprolite) showing B and C horizons --
Athens, Georgia
- Weathered
granite below C horizon -- note clay seams developing along
joints. Athens, Georgia
- Cool
humid soil -- near Forks, Olympic Peninsula, WA
- Tropical
soil -- lateritic weathering of plutonic rock. Near Acapulco,
Mexico
- Temperate
soil -- young prairie-type soil (mollisol) developed on
Peshastin moraine near Leavenworth, WA
- Desert
soil -- aridisols developed on loess, Eastern Washington
- Caliche
cap -- caliche layer exposed at surface due to erosional
stripping. E of Las Vegas, NV
- Aerial
view of caliche cap -- E of Las Vegas, NV
- Paleosol
-- buried soil. "Dryden soil" exposed on E. bank of Wenatchee R,
near Dryden, WA
- Groundwater
effects -- iron oxide deposited in terrace sediments by
groundwater at permeability boundaries
[top of page] [surface
erosion]
Andre Lehre
Last updated: 24 February 2003