Jun 04 2007

water stained rock wall above the Colorado river outside of Moab

Published by at 6:34 am under daily,likes & irks,photos

red rocks above the colorado river

red rocks above the colorado river

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3 responses so far

3 Responses to “water stained rock wall above the Colorado river outside of Moab”

  1. Chrison 04 Jun 2007 at 2:45 pm

    Awesome. It’s been a while since I was out west. I miss it.

  2. sallyon 07 Jun 2007 at 3:25 am

    repeat. its too beautiful—“o world I can not get thee close enough……”

  3. Larry Con 07 Jun 2007 at 9:22 pm

    Water Stained you say?
    It is actualy called desert varnish or sandstone varnish. The following is snipped from Wikipedia but although it tells us alot about it the actual process for forming it still seems obsure to me.

    Wikipedia quote:

    Desert varnish forms only on physically stable rock surfaces that are no longer subject to frequent precipitation, fracturing or sandblasting. The varnish is primarily composed of particles of clay along with iron and manganese oxides. There is also a host of trace elements and almost always some organic matter. The color of the varnish varies from shades of brown to black.

    Originally scientists thought that the varnish was made from substances drawn out of the rocks it coats. Microscopic and microchemical observations, however, show that a major part of varnish is clay (which could only arrive by wind). Clay, then, acts as a substrate to catch additional substances that chemically react together when the rock reaches high temperatures in the desert sun. Wetting by dew is also important in the process.

    Another important characteristic of desert varnish is that it has an unusually high concentration of manganese. Manganese is relatively rare in the earth’s crust, making up only 0.12% of its weight. In desert varnish, however, manganese is 50 to 60 times more abundant. This significant enrichment is thought to be caused by biochemical processes (many species of bacteria use manganese).

    Even though it contains high concentrations of iron and manganese, there are no significant modern uses of desert varnish. However, some Native American tribes created petroglyphs by scraping or chipping away the dark varnish to expose the lighter rock beneath.

    Desert varnish often obscures the identity of the underlying rock, and different rocks have varying abilities to accept and retain varnish. Limestones, for example, typically do not have varnish because they are too water soluble and therefore do not provide a stable surface for varnish to form. Shiny, dense and black varnishes form on basalt, fine quartzites and metamorphosed shales due to these rocks’ relatively high resistance to weathering.