This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Saturday, February 12, 2011

Namibia declares its whole coastline as a national park

Landsat 5 image May 26, 1992. From this reference.
The (British) Telegraph and the New York Times reported today that Namibia has designated its whole coastline as a national park. Becoming the first country to do so, the coastline park joins up with angola's Iona National Park in the north and South Africa's Richetersveld National Park in the south.  Namibia has long pioneered the use of tourism to fund conservation and supported its tribal communities to set up conservation areas to promote tourism and keep poaching at bay.

The Namib Desert is believed to be the world's oldest desert.  One park that is now included in the large park, the Namib-Naukluft National Park, originated in 1907. The area is ever changing, with the coastline advancing in the off shore direction.  In 1909 a passenger ship, the Eduard Bohlen, wrecked and crashed ashore.  It is now 1200 feet inland from the coast.   In the photo above, notice the dunes nearest the coast (toward the bottom left of the photo) pointing in a northeasterly direction, evidence that the coast line is expanding according to this reference. Two spits (at Sandwich Harbor and Walvis Bay) are also evident in the photo. These are formed by interaction between the southwesterly wind and the offshore Benguela Current.

Evolution of a linear dune
from Bristow et al. , 2000
Namibia is famous for its linear dunes, dunes that are parallel to each other as in the left side of the Landsat photo here.  Some of the worlds largest are situated here in the Namib sand sea. In 2000, Bristow et al. used ground penetrating radar to investigate the 3-D structure of a linear dune in an effort to figure out how these dunes migrate (Bristow et al., Nature, vol. 406, pp. 56-59, 2000). They recognized five stages in the evolution of the dune, illustrated in the Figure: (1) Formation of ripples on the desert sand; (2) Development of a dune with a relatively straight crest. This dune migrates in response to the dominant wind direction, producing planar set beds, called cross-stratification.  (3) Development of an instability that results in a sinuous, snake-like crest-line of the dune. The dune is now so big that a single wind season cannot re-sculpt the dune, and it develops a shape that is controlled by more than one wind direction.  Now there are two opposing sets of cross-stratification as shown in the illustration. (4) Complex superimposed dunes appear; and (5) Things get really messy!!

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