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L51 Weathered granite rocks in a wall. Cornwall, UK
Position:
N50° 11.4'
W005° 33' approx.
Elevation:
600' / 180m approx.
Image format:
35mm
WEATHERED GRANITE IN A WALL
GRANITE is a rock that forms from the cooling of hot, liquid MAGMA
under great pressure, within the Earth's CRUST - see L48 in the regolith.com library. When it comes into contact with
the atmosphere it changes in many ways. These changes are caused
by what we call WEATHERING PROCESSES. See the magnificent Granite
Landscapes of Yosemite National Park in L28 and L50 that have been formed by a combination of weathering and EROSION
processes.
Rainfall is often mildly ACIDIC - the acids attack some of the
MINERALS in the granite. Alternate FREEZING and THAWING of water
in cracks and spaces within the granite leads to disintegration
(see L29). These, and other processes lead to the gradual weathering of
granite and all other types of rock exposed at the earth's surface.
Compare this granite wall which is probably no more that 300 years
old with walls made of SANDSTONE in B2 (around 1200 years old). The sandstone is much less weathered
because it is largely made of the QUARTZ, a MINERAL that is very
resistant to weathering. Granite consists of some quartz along
with MICA , FELDSPAR and other minerals that are easily weathered.
Less detail
Image Trail:
L1 Balancing Rock. Arches National Park. Utah, USA.
L53 "Mitten Buttes" Monument Valley. Utah, USA
L54 Balanced Rock, Canyonlands National Park, Utah, USA
L60 Landscape Arch. Arches National Park. Utah, USA
L61 An evolving Arch. Arches National Park. Utah, USA
L62 The End & the Beginning of Arches. Arches National Park. Utah,
USA
L84 Weathered granite, Cornwall, UK
L85 Logan Stone, Cornwall, UK
L86 Solution hole in granite, Cornwall, UK
L87 Weathered limestone, Yorkshire, UK
Links:
http://geography.com.sg/weathering/index.html |
