Pantai Tengah - Honeycomb Weathering
Honeycomb Weathering - Tafoni
Honeycomb weathering, so named
after the honeycomb-shaped rock formations, also called Tafoni
(singular: tafone),
is a special and noticeable form of weathering that occurs primarily in
medium and
coarse-grained rocks such as sandstone, greywacke, granite,
granodiorite and gneiss but also some types of limestone. The name
tafoni comes from the Corsican word
"pietra tafunata", which means "perforated stone". The process of
tafoni formation is known as tafonation. During tafonation, chemical
and physical weathering processes in the rock create concave,
cavernous, spherical to kidney-shaped cavities with a diameter of a few
centimetres to several metres, which are usually open on one side. If
the cavities are only small and occur close together in a more or less
regular pattern that is remotely reminiscent of honeycombs, this is
also referred to as honeycomb weathering.
There are various theories about the origin of tafoni or honeycomb
weathering, and the exact formation processes are disputed. It is
assumed that these striking formations are formed polygenetically
through both physical and chemical weathering processes, such as marine
abrasion, salt weathering, wind corrosion and solution weathering.
Tafoni are formed by so-called core softening from inside
out:
The chemically dissolved binder is washed away by water or blown out by
the wind, leaving the cavities. The salt content of the water and air
(salt input with the fog carried inland from the sea) and the duration
of the drying periods between the wetting of the rock contribute to the
formation.
These characteristic box- or honeycomb-shaped cavities are found
worldwide in all climatic zones, predominantly in arid and semi-arid
dry regions, deserts and semi-deserts, and coastal areas with
significant tides. The best-known occurrences are in the Mediterranean
region (Corsica, Sardinia, Elba, Spain), the Atacama Desert, Australia
(Kangaroo Island, Uluru), and Antarctica. Tafoni can also occur in
stone structures
such as buildings and breakwaters if the local climatic conditions are
favourable. For example, you can sometimes discover characteristic
honeycomb formations in sandstone and greywacke blocks in coastal quay
walls.
Your task to log this Earthcache
as found:
Send your answers to the following questions via message to
my account (in English or German):
1.) Examine the honeycomb weathering
on site more closely. How small are the smallest honeycombs, and how
large are the largest (diameter and dephth)?
2.) The honeycombs are found on site in the bedrock. What does this
bedrock look like (structure, color)? What type of bedrock could it be?
3.) How do you think the honeycombs have been formed?
4.) Optional you can post a
picture of yourself or your gps in front of the
site, if you like!
Attention: There is
no need to wait for a log permission! You can log the cache as found
after you sent me the answers - if there's something wrong, I'll
contact you!
Have fun and enjoy the location!
Silberschakal
Sources:
Ahnert, F. (1996):
Einführung in die
Geomorphologie. Stuttgart.
www.mineralienatlas.de
www.spektrum.de
www.tafoni.com
www.wikibrief.org
www.wikipedia.org
The pictures were taken by the author.
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