17 January 2012

The ventifacts of Rooiels

Posted by Callan Bentley

Site of the mystery photo I posted over the weekend, the beach at Rooiels (“red grass” in Afrikaans), South Africa, is a lovely place…

Located on the western side of False Bay a tad north of Cape Hangklip, Rooiels is somewhat famous in my mind because the Guru of Gigapan, Illah Nourbakhsh, spoke glowingly of it at the November 2010 Gigapixel Imaging for Science conference in Pittsburgh. When I finally got the chance to visit South Africa myself this past December, I made a point to stop in for a look around this legendary beach.

In addition to the wild beauty of the place, there is also some intriguing geology. One thing I was struck by there was the presence of bedrock outcrops on the beach, and the prevailing southeasterly winds. These winds pick up sand and slam it into the outcroppings, sandblasting their eastern face. All the rest of the photos in this post are taken from the south, looking towards the north. Compare the rough western faces (left) of these rocks with the smooth, scalloped eastern faces (right):

These are ventifacts: rocks that have experienced significant erosion not at the hands of the usual suspects, water and glacial ice, but instead by wind. These sandstones have been sandblasted!

If you zoom in on this one, you can see some nice fluting parallel to the pen:

This one is my favorite. Only with a consistent prevailing wind direction are you going to get something that looks like this:

A downwind view (i.e., facing west) can be seen in this GigaPan that Illah shot on the beach in Rooiels.