Monday, 24 September 2007

A painted desert?

After the stars and stripes of yesterday, today's view from the air near to Mark's route reveals this amazing display of rainbow rocks. These are folded sedimentary rocks -laid down in ancient seas as layers of different types of sediments - sandstones, mudstones, shales, clays, gritstones, limestones etc - each layer with its own geologic properties and colours. The collision of great crustal plates in the last 60 million years resulted in these layers being uplifted and folded to reveal their glory in mountains rising to heights of 2000 metres. It is through here that Mark has been cycling today.

The beauty of the colours is even more apparent in a closer view. The change of hue is so subtle it reminds me of a shade card! However, there is more in the view than just colourful rocks.....

The 'river' is a wadi which , viewed nore closely, will look like this . Wadis are dry river beds filled with sediments carried when the rivers are in seasonal flash flood mode. These rivers rise very quickly in response to the rare rain events but their levels also fall quickly as the water is absorbed and evaporated, depositing the sediments in the river channels.

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