Ron Schott is hosting the latest Accretionary Wedge. He is asking us to recall the most memorable/significant geologic event that we have directly experienced. I have lived my life in very geologically stable places so this topic may seem a bit odd as my first entry for the Accretionary Wedge. There has been some neo-tectonic activity with small earthquakes in Namibia and the Western Cape, South Africa, but I have not felt any. There was also apparently an earthquake near Cape Town in my first year at university. I didn't feel that one either. I have traipsed across active faults and volcanoes but fortunately non ruptured or erupted while I was there. The youngest volcano I've lived next to is Regenstein, on the outskirts of Windhoek, and that last erupted in the early tertiary (the only age I can find; Pirajno, 1994) and is extinct. When it comes to geologic hazards, I have lived a sheltered life.
My sister-in-common-law and her husband used to live in Christchurch. It was scary when we couldn't contact them during the 22-Feb-2011 earthquake. Fortunately they were ok, although, their office buildings have been either demolished or condemned. There was a slim chance that we would be spending this christmas in Christchurch. However, they moved the week before we arrived in New Zealand. They now live on the North Island and I am charged with keeping them abreast of volcanic developments. My Partner was in Christchurch for the boxing day earthquake 2010 and in Brisbane during the floods in January 2011 (he just missed the cyclone). Me? I was in nice, stable and politicians aside, non-crazy Southern Africa. Windhoek, Namibia to be precise. What could I possibly experience in Windhoek that would fit the guidelines of Accretionary Wedge #41?
Windhoek is supposed to have an average rainfall of about 350mm per year. Normally we are grateful for rain. We might even consider investigating the merits of rain-dancing. When Windhoek rivers flow many (most?) people in Windhoek go down to the banks to watch the standing waves go by and children play in the parts flowing slowly. Summer in Windhoek, you see, is usually hot and dry.
|The hills on the southern edge of Windhoek. December 2010|
|Not very green and not much grass to speak of. December 2010. Jill Russell |
(aka Jilly Bean) smiling at the camera
In January last year it was different. Last year we had 383.6mm of rain in January alone. By the start of winter Windhoek had had over 1000ml of rain! By the start of winter we were all rather damp and sick of rain. Our roads were full of pot-holes and in some cases washed away all together. There are three bridges, I know of, across the Klein Windhoek River, Windhoek's main river. The roads the river crosses tend to be added to its sediment load.
This unusual rainfall occurred across the country. There was flooding in the North. The Sesriem Canyon was full of water and Sossusvlei was flooded in the South. I spent a weekend in Henties Bay. It rained on our first night. Henties Bay is in the desert. Rivers in Windhoek and across Namibia were still flowing in May. Unheard of! Then in winter it actually snowed. Just a dusting in Windhoek and a bit heavier in the South. It last snowed in Namibia in about 1995.
|Exactly the same slope as the first picture. January 2011|
|The hills on the southern edge of Windhoek, January 2011|
And there you have it the most significant earth science related event I have experienced directly, to date. As for Windhoek? So far this summer has been business as usual, piping hot and dry, with all the people I know in Windhoek looking at the sky, searching for the welcome glint of a cloud.
Pirajno, F. 1994. Mineral resources of anorogenic alkaline complexes in Namibia: A review. Australian Journal of Earth Sciences, pp. 157-168.
More photos from Windoek. These are of Avis Dam on the eastern edge of the city.
|Avis Dam flood plain, Windhoek, December 2010|
|Avis Dam flood plain, Windhoek, January 2011|
|Rail bridge, and river feeding Avis Dam. Windhoek, beginning of January|
|River flowing into Avis Dam. Windhoek, 22 January 2011|