Where on Google Earth #253
    By Gareth Fabbro | January 18th 2011 01:13 PM | 5 comments | Print | E-mail | Track Comments
    About Gareth

    For those of you who are not geologists, a tuff is a volcanic rock, made up of solidified ash. Hence the pun as my blog title. Actually, my research...

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    As Where on Google Earth #252 was somewhere I know well, having studied a course that was almost entirely dedicated to the tectonics of the region (which included a fieldtrip), I'm quite glad I managed to work it out.  The fan delta in the centre of the coastline shown is just one of many in the region, formed due to the interaction of the faults uplifting the mountains to the south and the sea.  There are also some spectacular outcrops of faults planes exposed in quarries, where the fault surface has been preserved due to its burial.  Perhaps the most spectacular example of this is in a similar tectonic setting to the north on the Gulf of Malia, at Arkitsa.

    Anyway, on to WoGE #253.  The goal of WoGE is to find the location of the picture below from Google Earth.  The first one to post the correct answer in the comments below, along with a short description of the Geology wins.  The prize: the chance to host WoGE #254 on your blog!  Once again, we are indebted to Brian Romans of Clastic Detritus for the creation of this format.

    Because I think this one is fairly easy, a classic location and a wide field of view, I am hereby invoking the Schott Rule.  That means that newbies should have a chance, previous winners have to wait before they post an answer.

    WoGE #253

    Good Luck!

    (This was posted at 20:15 CET/GMT +1, in case the timestamp on the post is not clear)


    Hmm... doesnt look that easy to me. I tried a few places in the Middle East, but no luck so far. What's happening on the right side? Almost looks like an accident/disaster

    30°58'N, 60°32'E Sefidabeh blind trust
    Sefidabeh is built on an old 'alluvial fan', formed where an ephemeral river that used to flow through the ridge discharged its water, and with it sediment known as 'alluvium', onto the desert plain. But as repeated earthquakes caused the ridge to grow, not just in height but also by increasing its length towards the north-west, the river had to
    incise a gorge through it, eventually becoming blocked, and forming a lake. Finally the river abandoned this course altogether, and now flows round the north-western tip of the ridge instead. The old lake beds remain, now
    dry and elevated 70 metres above the desert plain. From the age of the sediments within them we can date the switch in the river course to about 100 000 years ago. The full story can be found here:

    Spot on!  Back to you for the next round.

    The Sefidabeh blind thrust.  The 1994 initially confused seismologists; the seismology showed clearly that the earthquake motion was along a thrust (or compressional) fault, but the trace found in the field was of a normal (extensional) fault and much too small.  However, when it was realised that the ridge was growing (by working out the history of the river) this mystery could be explained.  The main fault is a thrust fault, but it does not break the surface.  Instead, the compression at the surface is taken up by folding, and with each successive earthquake the ridge grows.  The normal fault found at the surface was due to this folding, because bending stuff requires the upper surface to extend (try bending a rubber).
    *sigh* and that's *another* destination to add to my "Big Geological Holiday of 2015" list.