Download Weathering - WBR Teacher Moodle

Weathering
From
http://www.geosci.unc.edu/faculty/glazner/Images/Weathering/weathering.html
Classic sheeted granite along the Tioga Road, Yosemite National Park. The
granite is broken into gently dipping plates by unloading joints. Unloading joints
probably form as the rock is exposed by erosion. These joints, and others that are
more steeply oriented, provide pathways for water to enter the rock.
Mt. Brewer (13,570') in the Sierra Nevada. Looks like
a solid hunk of rock, right? See next slide.
The east ridge of Mt. Brewer (the easy way up), near the summit. This mountain,
like most in the Sierra, is covered by a thick layer of sharp-edged boulders
produced by frost wedging. Frost wedging is well-developed here because the
temperature cycles across the freezing point many days each year.
Rounded boulders in Joshua Tree National Monument, California. This
park is famous for its rock climbing and its cactus forests. Rounded
boulders like these reflect long-term erosion of granitic rocks by frost
wedging and chemical weathering.
Deeply pitted surface of limestone in a desert
environment. Rainfall erodes the limestone into pits
and channels by dissolving it.
Cavernous weathering of granite on the island of Paros, Greece. This sort
of weathering is common along many coastlines and probably results
from deposition of salt in cracks (salt wedging).
A wooden post that soaked for many years in a pool of brine in Owens
Lake (dry), eastern California. The grotesque swelling of the wood results
from deposition of salts in the wood.
In the desert many rocks take on a dark coating of manganese oxides known as desert
varnish. Native Americans inscribed petroglyphs on these rocks by scraping away the
varnish, exposing lighter rock beneath. Coso volcanic field, California.
A bizarre form of mechanical weathering: Mushroom Rock, Death Valley National Park.
Mushroom Rock was carved by blowing sand. The upper part of the rock is relatively
uneroded because the windblown sand is densest a few feet above the surface. This rocks,
which was about 2 meters tall, has since fallen down.