A mass of rock which forms underground is under enormous pressure because of the material on top. As geological processes bring the rock to the surface, the material pressing down on is is slowly removed by processes of erosion. When the rock is finally exposed, all the pressure that has been keeping the rock in check has been removed.

Now, plutonic rock isn't a particulary plastic substance, and the rock will not slowly expand under release of pressure, it will break. In particular, stress fractures will form parallel to the surface of the rock. When exposed to the elements, water will get inside the cracks and freeze, prying them open even further. When the water dries up, salt crystals grow in the cracks. These fractures eventually cause plate or leaf-shaped pieces of rock to break off.

Sometimes these plates are tiny, other times they are enormous. In July 1996, a 31,500-ton slab of granite fell off Glacier Point into Yosemite National Park's Happy Isles Visitor Center, killing a tourist. In 1999, a 25-foot long slab of granite fell off Panorama Cliffs into the Yosemite valley. This killed one climber and forced the evacuation of Curry Village, one of the park's principal campgrounds.

As a mass of rock continues to exfoliate, it takes on a rounded appearance. When such remnants are the size of mountains, they are called "exfolation domes", such as the ones in Yosemite Valley (although these have been modified into Half domes by valley glaciers which have ground half the mountain away).

Cosmetically speaking:

The use of a scrubbing medium to remove dead skin cells, dirt, and other detritus from the surface of (uh... living) skin. Widely touted as an acne prevention measure, exfoliation is typically done daily or weekly (in the case of sensitive skins).

Technically, you exfoliate every time you use soap, since the use of any soap is mildly (I did say mildly) abrasive.

To go a step further, humans spontaneously exfoliate every second, simply by dropping dead skin cells in their wake. To observe a model of the phenomenon, hold a very pissed-off, soft-haired cat in the air for several seconds and observe the air around it.

The Cult of Exfoliation:

It is highly addictive. Freshly exfoliated skin feels wonderful. Keep an eye on your teenage daughters; that fresh, glowing look may be the door to a lifelong problem.

In many families, the introduction of an exfoliation regimen is a rite of passage. From babyhood baths, on to adolescent acne prevention products, exfoliation progressively encourages deeper dedication and time commitment through the years. Soap may be considered a "gateway exfoliator".

Clinique advertises exfoliation as the solution to the majority of problems afflicting any life form on earth. Since they also market some of the most powerful exfoliators available without a prescription, one wonders about their motives.

A recent television advertisement for St. Ives' Invigorating Apricot Scrub ("Gently exfoliates dull surface cells to reveal glowing, fresh, healthy skin") went so far as to admit the almost religious nature of the exfoliation experience. Don't ask me how I know what the Apricot Scrub bottle says. You have to know these things when you are investigating the exfoliation underworld.

As many beleaguered boyfriends will admit, strong exfoliators can be slightly painful, particularly when followed by astringents. I mean stuff like witch hazel and isopropyl alcohol. Go ahead, do it. I dare you. This adds to the whole rite of passage mystique.

You may find yourself offered free samples of exfoliant in shopping malls or other "safe" locations. Be aware of the risks. That is all.

Ex*fo`li*a"tion (?), n. [Cf. F. exfoliation.]

The scaling off of a bone, a rock, or a mineral, etc.; the state of being exfoliated.

 

© Webster 1913.

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