Tuesday, November 22, 2011

WOGE 320

Thanks to Felix Bossert for providing an easy and unrestricted WOGE 319.  I happened to log on at the right moment, and I was able to find Hiti Atoll in the South Pacific easily just by flying aimlessly over some of the areas where coral atolls are common.  Thanks to Péter Luffi also, for graciously waiting just long enough for me to post my comment first :-)

Now, what to post for WOGE 320...  Thanks to Felix again, for your suggestion!  I have seen this joked about, but I don't know if anyone has actually done it.  So here it is -- A single sand dune in the middle of a desert.

I will upload larger views if it is necessary, but I suspect this may be an easy challenge for some players.  As always, the first person to find this location with Google Earth and provide a brief description of the geology wins the privilege of providing the next challenge. I will invoke the Schott Rule this time, just because no one has used it in the last month.  If you don't know what the Schott Rule is, then check out the New Players section at Felix's blog.  Posting time is 3:05 UTC

It has been a few days, so I am providing a more standard view.  This is technically a "historical image", but the part with the sand dune is exactly the same.  When you find the location on Google Earth you might notice that something interesting happened in the ten days after this image was made.
I did not expect that this would be a difficult challenge, but now I suspect that everyone may be looking in the wrong deserts.  I would rather not give an even larger view, since it would make things too easy.  Instead, I give you a close-up view of part of the dune at top center in the second image.  I hope that a careful look at this will give someone the hint they need to find the proper desert.  If you have already spent more than fifteen or twenty minutes searching in a particular country, you are probably on the wrong track.
The second picture above is just for comparison.  It is at the same scale and was taken on the same day of the year but, obviously, in a different part of the world.  I hope it makes the hint more clear.


  1. Thaat's a nice one! And it's even round. I have to admit that I am a little jealous to not have found that before ;-)

  2. @Matthew: do you want to highlight the color of the sand?

    I think we are not looking at a huge desert. As this is a huge dune, not moving (little trees), I think we are close to the sea. The wind blows from south to north. From my previous sailing experiences it could be a wind system, blowing parallel to the coast. The question for me would be: east coast or west coast.

  3. The color of the sand is useful, but is not the main hint. The hint is only noticeable because I included the image date on each picture and used dunes that have slipfaces oriented roughly the same direction.

    As for your other conclusions: 1) You are correct that this is not a huge desert. 2) The dune is moving, but slowly. Some of the little trees are actually bigger trees that have been almost completely buried. 3) The constant south winds you recognized do come from the coast, so we are not a huge distance from the sea. However, this is not actually a coastal dune either, since the sand has never been on the beach. 4) The wind system does blow more-or-less parallel to the coast. 5) East or west coast? Well, that would make it too easy:-) However, when you realize what the hint actually is, then the rest of the clues you have already noticed should allow you to focus your search on just one country, and you will find the location within a few minutes.

  4. @Matthew: Thank you for your explanations. Im not really searching as at the end of the year everything is busy and I have nothing in stock for a new WOGE. I strongly hope our huge american community should have digested the pumpkin filled turkey by now and is going to solve this wonderfully chosen WOGE.
    Or is there nobody out there?

  5. This was a tough one: 5.6557S 80.6128W - sand dunes at Lago la Niña, an intermittent lake in Bayóvar Peninsula, northern Peru. It appears that the sequence of images taken at 2/22/2011 and 3/4/2011 catches some serious flooding in action, which fills up the lake. Rolling back in time illustrates similar changes in the water level (~max. level in the first image taken at 2/1/2003; then in the 3/16/2004 and 12/1/2004 imagery the lake appears to be completely dry). Everything else relevant to these images was nicely put by Felix, so I won't repeat that.

  6. @Péter: Congratulations. I think the red "river" in the historic picture, dated 1/22/2004 has something to do with algaes. I think I have read something about algaes in salt lakes at WoGE295 (http://andiwhere.wordpress.com/2011/06/29/where-on-googleearth-woge-295/)

  7. Congratulations to Péter Luffi for finding the right sand dune in the coastal desert of northern Peru and pointing out how Google Earth nicely captures the periodic flooding of the lake bed.

    My hint was that the dune at 15.966S in the lower image is clearly being lit from the north and east, while the WOGE dunes show almost no north/south contrast. Since the sun was passing nearly straight overhead on March 4, the WOGE had to be just a little south of the Equator. There are only two arid regions at that latitude: East Africa and Coastal Peru. Only Peru has the steady South winds needed to create such a perfect crescentic dune.

    I look forward to seeing whether Péter will give us an easier WOGE or make us all work hard again.

  8. I knew it from the first glimpse that this is somewhere in the Southern Hemisphere, but never thought it might be so close to the Equator. No wonder it took me so much! Regarding these shadows... yeah, it seems I need to work on calibrating my eyes to distinguish the effects of latitude from those of dune slope angles. But I'm open to suggestions :-)

  9. I first found this location while researching dunes after I found WOGE 276. Back then the image on Google Earth was the 1/22/2004 version, with the dune clearly lit from the south. That would have really thrown everyone off track :-)