Geo-ing on Holidays

Work has been rather quiet over the past few weeks – I made the most of my annual leave this year by heading off on travels around Australia. An exhausting but refreshing few weeks taking in the semi-arid interior and the sometimes very wet coastal regions. On the way to Uluru though, I couldn’t help but be reminded of work, as we flew over vast areas of the arid ‘Red Centre’ of the continent. The views over these beautiful landscapes, with relatviely little variation, show geomorphology very much in action. I spent a lot of the (non-cloudy!) parts of the flights with my nose pressed against the window, tracing the cycles of deposition, erosion and deposition again, by wind, water and gravity.

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Drainage channels eroding sediments, Northern Territory. Photo: R. Inglis

In the photo above, you can see the fractal structure of the drainage channels that mark the paths of rainwater, flowing from the centre right of the image to the bottom left corner. These channels are marked by vegetation, a result of the rains that have fallen in this, and recent, years. Starting to the left of the reddish band in the right of the picture, they are very small,  gradually joining together to make larger channels. The different colours of the landscape along these channels show the bedrock and sediments exposed by this erosion – from the reddish, uppermost sediments on the right of the picture through the paler underlying sediments. The return to reddish sediments to the left of the picture may be the result of re-deposition of the sediments from the right by water action – but you’d probably need to get out there and have a poke with a spade to check!

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Dunes eroding into Kati Thanda-Lake Eyre, South Australia. Photo: R. Inglis.

Cheating slightly now, my favourite geomorphology photo from the skies over Australia so far is one I took on the way back to the UK in July. Above, the right of the picture is dominated by Kati Thanda–Lake Eyre, a lake that fills intermittently with floodwaters from rivers in Queensland and the Northern Territory. The water then evaporates, leaving the thick salt crusts you can see as the white band bordering the water. The left of the photo, however, is dominated by long, linear dunes, formed by wind blowing sand during arid periods. The beauty of this landscape for me is that these dunes are currently being eroded by gullies and channels that empty into the lake, forming, as can be seen by the dark scallops along the edge of the salt – tiny alluvial fans and deltas of sediment. when these fans, and the lake, dries out, they become major sources of sediment that can then be blown by the wind, which once more forms dunes (see the post on Lake Mungo and its lunette) and the cycle begins again.

This geo-spotting from the air doesn’t just (for me anyways) pass the time on a long-haul flight. The new perspective that viewing landscapes from the air gives geomorphologists is an invaluable tool for understanding both the processes shaping a landscape today, as well as the signatures of the processes that operated in the past. It is the low-tech, but immediate relation of analysing satellite and aerial photography to learn about landscapes – exactly the task I have returned to at the end of a fantastic month away!

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