Kaapse-erosion EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
In the Provence of Mpumalanga there is a small little town
called Kaapsehoop and on the outskirts of this little town there is
a rock field of the most amazing erosional features you'll ever
see.
The village is set on a plateau amidst a massive rock field of
detached rocks. The rock field formations are comprised of
quartzites of the Black Reef Formation of the Transvaal
Supergroup.
We know these strangely weathered rocks as shallow-dipping
quartzites of the black reef formation. The almost horizontal Black
Reef Formation forms a hard, resistant layer over older Godwan
Formation, which in turn, rests on abasement granite-gneiss,
clearly visible on the Kaapsehoop pass.
On the Ngodwana road you will see typical outcrops or the Malmani
dolomite that overlies the Black Reef.
Through the process of erosion the softer rock and minerals in the
Black reef have been weathered away leaving the eerie formations of
the rock field.
These rocks apparently reminded the diggers and farmers of the
walls of a room and the regular thick mist gave the place a gloomy
atmosphere, hence its original name, Duiwelskantoor (Devil's
office).
Below are explanations of different types of erosion that could
possibly have contributed to the creation of the formations that
can be found here.
The process known as weathering breaks up rocks so that they can be
carried away by the process known as erosion. Water, wind, ice, and
waves are the agents of erosion that wear away at the surface of
the earth.
Water Erosion
Water is the most important erosional agent and erodes most
commonly as running water in streams. However, water in all its
forms is erosional. Raindrops (especially in dry environments)
create splash erosion that moves tiny particles of soil. Water
collecting on the surface of the soil collects as it moves towards
tiny rivulets and streams and creates sheet erosion. In streams,
water is a very powerful erosional agent. The faster water moves in
streams the larger objects it can pick up and transport. This is
known as critical erosion velocity. Fine sand can be moved by
streams flowing as slowly as three-quarters of a mile per
hour.
Streams erode their banks in three different ways:
1) the hydraulic action of the water itself moves the sediments,
2) water acts to corrode sediments by removing ions and dissolving
them, and
3) particles in the water strike bedrock and erode it.
The water of streams can erode in three different places:
1) lateral erosion erodes the sediment on the sides of the stream
channel,
2) down cutting erodes the stream bed deeper, and
3) headward erosion erodes the channel upslope.
Wind Erosion
Erosion by wind is known as aeolian (or eolian) erosion (named
after Aeolus, the Greek god of winds) and occurs almost always in
deserts. Aeolian erosion of sand in the desert is partially
responsible for the formation of sand dunes. The power of the wind
erodes rock and sand.
Ice Erosion
The erosive power of moving ice is actually a bit greater than the
power of water but since water is much more common, it is
responsible for a greater amount of erosion on the earth's surface.
Glaciers can perform to erosive functions - they pluck and abrade.
Plucking takes place by water entering cracks under the glacier,
freezing, and breaking off pieces of rock that are then transported
by the glacier. Abrasion cuts into the rock under the glacier,
scooping rock up like a bulldozer and smoothing and polishing the
rock surface.
To claim a find here you'll have to do the following:
1)Take a photo of yourself and your GPSr at the most amazing
feature you can find and mail it to me, &
2)Take a good look at the erosional features and tell me via e-mail
what type of rock you think they're made of.
Additional Hints
(No hints available.)