Geology of Sochi II: the basin In my last post, I covered the geology of the mountains which tower o

Geology of Sochi II: the basin In my last post, I covered the geology of the mountains which tower over Sochi, Russia, and discussed how the mountains are built by a series of faults (see here: http://tinyurl.com/l6upzzm). Another major feature of the area is the Mzymta River, seen here where it enters the Black Sea. All of the Olympic venues are located within this valley. The river is sourced in the high peaks of the Caucasus and winds its way to the coast, crossing several waterfalls and the Dzykhra and Akhshtyr rivers. The river’s flow is regulated by hydro-power stations and is a popular tourist site for rafting. Many of the Sochi venues sit on sediments deposited by this river. Sochi itself sits in a tectonic lowland, south of the thrust faults in the mountains, known as the Rioni basin. A basin sitting at the base of thrust faults is a very common setup caused by gravity. As a mountain range builds, its weight pushes nearby rocks downwards, creating a basin that will commonly be filled by sediments derived from erosion of the mountains. Typically, as mountain ranges grow, their faults will penetrate into these basins and they will be incorporated into the growing range. The Rioni basin sits between the Caucasus and the Black Sea in this area and it is filled in part with sediments brought down from the mountains along the river. For construction of large facilities like the Olympics, this setup creates enormous potential problems due to the combination of active faults and sediments. When an earthquake happens near a sediment-filled basin, the sediments tend to focus the energy. As they shake, the fine-grained sediments mix with water and undergo “liquefaction” – basically losing all strength and flowing like a mudflow. If a building is sitting on top of sediments that are shaken in an earthquake, it will be very difficult for the building to survive. The area around Sochi is a mix of sandy beaches, bogs, and wetlands. The ground remains waterlogged and the area gets heavy rains and floods often. Constructing an Olympic village in this area required developing drainages to move the water, pouring foundations stable enough to survive earthquakes and liquefaction, and then building the facilities on top. The geology of the area made the construction of these facilities a difficult, expensive proposition regardless of whatever else went on. -JBB Image credit:http://en.wikipedia.org/wiki/File:Mzymta_River.JPG Read more:http://blogs.scientificamerican.com/rosetta-stones/2014/02/03/building-sochis-olympic-village-an-olympic-task-in-a-geologically-risky-area/ -- source link
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