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A Tor in the Desert

A Tor in the Desert
Photo Information
Copyright: James Parker (Jamesp) Gold Star Critiquer/Gold Note Writer [C: 1369 W: 9 N: 6334] (18906)
Genre: Landscapes
Medium: Color
Date Taken: 2007-01-11
Categories: Desert
Camera: Canon EOS 1Ds MkII, Canon 24-70 mm f 2,8 L-USM
Exposure: f/9.0, 1/320 seconds
More Photo Info: [view]
Photo Version: Original Version
Date Submitted: 2007-07-14 5:28
Viewed: 7880
Points: 28
[Note Guidelines] Photographer's Note
I took this shot near the 4th Cataract of the Nile in January. It shows a perched granite boulder which is part of a tor. There are notes below on how tors are formed.

As hot but solid granite cools, contraction causes the formation of joints (open fractures) usually near vertical, in the granite. Hot water moving through these joints commonly leads to their becoming lined or filled by minerals such as quartz or a black mineral called tourmaline or both. The orientation of the joint pattern is controlled by pressure in the earth’s crust. The joint pattern is accentuated and modified by actual movements along the fractures.

Kaolinisation is one of the important processes leading to the breakdown of the
solid granite. It is caused by the circulation of water that has been heated within the granite. The feldspar minerals comprising some 30-40% of the granite are decomposed forming the white clay, kaolin. This starts the process of shaping the tors as the surrounding granite is softened and weakened in places. The kaolinisation process probably continues for a considerable length of time as heat continues to be generated in the granite by its natural radioactivity.

The next major tor forming process is weathering - water containing acids from rotting plants is very reactive and the minerals, again mainly the feldspars of granite, were attacked and weakened. The more stable mineral quartz was much less affected. The weathering mainly took place along the lines of the joints through which water moved. Where joints were closely spaced the individual mineral grains of the granite became more or less completely separated to a considerable depth.

The rounding of the granite blocks is a result of both chemical and mechanical weathering. Firstly, exfoliation plays a part. Chemical processes cause the surface of the blocks to expand and/or shrink. Thin layers of rock come off the boulder. This rounds the granite block, because the chemical processes have more effect on areas with edges. These processes cause the rock to look like it's made of layers like an onion. In effect, only the outer few centimetres are affected by chemical weathering. This process is called spheroidal weathering. Secondly, the boulders are suffering from solarisation. Because the temperature differences between day and night are so great, the rocks expand and shrink a little bit every 24 hours. This causes some rocks to crack, sometimes even splitting them in half.

pirate, lovenature, XOTAELE, cicindela, JORAPAVI, nglen, vanderschelden, mikou, delic has marked this note useful
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Critiques [Translate]

Lovely picture most interesting with your note

Hi James
Mother Nature really creates some beautiful artwork. Your note is very interesting. I find it fascinating how these rock are formed. The earth sciences really intrigue me. If you want check out my Hoodoo it's really unique.

Excellent capture, colour and detail.
TFS Janice

Hola James.
Una sensacional formación rocosa muy bien explicada por tí en tu comentario.
Buenos detalles y estupenda nitidez.
Un saludo y tfs, JL.

Dear James,
Someone could say that these are "only" the stones, but I think that it is also a very unique rocky composition. I like colours and POV, which together with excellent and very detailed note make this presentation very interesting.
TFS and best regards,

PS. It there any country in the world not visited by you? ;>

Hola James,
Interesante y curiosa imagen con una nota muy completa, la naturaleza no deja de sorprendernos con estas curiosidades, TFS. Saludos
José Ramón

selam, Great shot and very good composition nice pov and bg with splendid colours. Well done ! Regards ridvan

  • Great 
  • joey Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 1739 W: 224 N: 6872] (24909)
  • [2007-07-14 10:47]

Hi James,
a great shot of this desert scene.
Sharp with a perfect composition.
Well done,

  • Great 
  • nglen Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 2883 W: 30 N: 9683] (36145)
  • [2007-07-14 14:05]

Hi James. a very nice picture. it looks like someone put it on the top of the other rock.great lighting and the shadow to the left . a perfect blue sky. great notes . tfs.

Hi James,
Nice view...
Good compo.

  • Great 
  • gannu Gold Star Critiquer/Gold Note Writer [C: 988 W: 4 N: 3277] (14761)
  • [2007-07-15 0:47]

James, Very nice and I am surprised how the rock is standing on the edge? Such things you can see plenty in India towards souther part. But this clarity of the picture is brilliant. Ganesh

  • Great 
  • mikou Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 869 W: 68 N: 1479] (6093)
  • [2007-07-15 3:26]

Hi James.
Beautiful clear picture and very interesting your note too.Great composition with very nice gentle nuances of colors and good details.Well done.
TFS,with greeting Milos.

hi james ,
very nice capture, i loved the tone of the blue sky in this shot which makes a excellent bg, lovely contrast, nice pov,
well done,
tfs & regards

  • Great 
  • arfer Gold Star Critiquer [C: 2731 W: 0 N: 0] (0)
  • [2007-07-17 4:37]

Hello James

I love the bold colours and the composition.The lighting is excellent.excellent focus and sharpness of detail.TFS


  • Great 
  • delic Gold Star Critiquer [C: 440 W: 6 N: 310] (898)
  • [2007-07-21 14:33]

Hi James,
Fine act of balance. Interesting erosion process explained and demonstrated perfectly. Regards,

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