Download Weathering

Weathering
Processes that break down rocks,
producing material that may
eventually become sediment
Chemical Weathering
 Involves chemical reactions that result
in the formation of new materials (e.g.
new minerals or ions carried off in
solution.
Baraboo quartzite, Wisconsin - note weathering rind
Hydration of feldspars --> clays
Modern soil developed on basalt, Oregon - Bruce Railsback
http://www.gly.uga.edu/railsback/FieldImages/OregonModernSoil.jpeg
Monument Valley, AZ - oxidation produces hematite
Detail of artwork
Detail of date
Slate gravestone - Amherst, MA - note lack of weathering
Slate stone - 1820
Marble stone - 1844
Note dissolution of calcite
Marble stone - Amherst, MA - consists largely of calcite
Differential weathering - lighter minerals more resistant
Mechanical Weathering
 Breaks rocks down into smaller pieces,
but without changing the mineralogy
Lamphier Lake, Colorado - note talus slopes
Frost wedging
 Water expands on freezing; liquid water gets
into cracks in rocks, then freezes and
expands - enlarging the crack & eventually
breaking off pieces of the rock
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Water seeping into porous sandstone
freezes - causing frost wedging and
spalling off of parts of the surface
Frost wedging and gravity produce
talus slopes in mountainous areas
Salt crystallization
I-80 Bonneville salt flats, UT
 Salty water is drawn upward in these fenceposts by
capillary action; crystallization of salt when the water
evaporates splits the posts! (similar to frost wedging)
The Old Man in the Mountain
Exfoliation: Cannon Mountain, NH