Weathering 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.