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L36 Weathering, erosion and deposition. Capitol Reef National Park,
Utah, USA
Position:
N38° 17'
W111° 16' approx.
Elevation:
6200'/ 1890m approx.
Image format:
MF 35mm
WEATHERING, EROSION & DEPOSITION
The essential point to understand about changes in the form and
appearance of the earth's surface - its GEOMORPHOLOGY, is that
there is a down-slope transfer of material by weathering and erosive
processes assisted by gravity.
This is well illustrated in the photograph. Material is weathered
on the exposed rock faces by heating and cooling, wetting and
drying, freezing and thawing and a number of chemical processes,
The combined effect is to break large rocks down in to smaller
pieces and to convert less stable chemical compounds into more
stable forms. The rocks and their constituent minerals, in other
words, breakdown and decay.
Meanwhile, rain and wind remove loose fragments from the cliff
faces and these accumulate on the lower levels where they are
reworked and re-deposited, mainly, by running water.
In this image fan-like accumulation of weathered debris are being
eroded by run-off GULLIES. These are the up-slope tentacles of
aggressive stream systems, which, though dry for most of the time,
are the main agents of landform change. A dry stream bed or WADI
dominates the foreground of the image. During FALSH FLOODS this
could be a dangerous place to be!
There are several major layers of rock or STRATA in this scene
from Utah's Capitol Reef National Park, USA. The dominant strata
forming the bold vertical faces are SANDSTONES. In between are
weaker, crumbly layers of rocks that are rich is clay.
WEATHERING processes attack the weaker rocks with most success
but fragments of all the represented rocks accumulate as SCREE
(also called TALUS). So in this view we have vertical CLIFF faces
and less steep SCREE slopes - two essential ingredients of a landscape
- the latter being formed by DEPOSITION or accumulation of WEATHERED
debris. Eventually, this weathered material will find its way
in to streams and will be washed away.
Less detail
Image Trail:
L4 River canyon cut through horizontal strata. Cataract Canyon,
Colorado River
L25 Gullied Butte - badlands. Grand Mesa, Grand Junction. Colorado,
USA
L30 Debris flow. Henry Mountains. Utah, USA
L32 Eroded escarpment. Utah, USA
L33 Eroded escarpment. Utah, USA
L34 Gullied Butte - badlands. Factory Butte, Hanksville. Utah, USA
L42 Badlands. Bryce Canyon National Park. Utah, USA
L43 Badlands. Bryce Canyon National Park. Utah, USA
Links:
many photographs of the rocks in this area at http://donb.photo.net/photo_cd/h/
http://geography.com.sg/weathering/index.html
http://geography.com.sg/rivers/index.html
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