Mont Blanc The Mont Blanc massif, on the border between France, Italy, and Switzerland, contains the

Mont BlancThe Mont Blanc massif, on the border between France, Italy, and Switzerland, contains the highest peaks in the Western Alps, with 11 separate summits at elevations above 4000 meters. Mont Blanc is one of several exposures in this area of rocks that were once buried tens of kilometers deep. The rocks in the massif started their lives over 300 million years ago during the Variscan orogeny, the mountain building event in Europe associated with the assembly of Pangaea. The rocks in this shot represent igneous and metamorphic rocks; batches of igneous rocks called plutons intruded into the surrounding rocks and metamorphosed them, creating a solid mixture of the two rock types.After Pangaea broke up, these rocks slowly settled down and were covered by hundreds of meters of sediment. Finally, a few million years ago, Africa began impinging upon Europe, faulting rocks upwards and thickening the crust. Eventually, thrust faults cut all the way down into the igneous and metamorphic basement in this area, and the deep, metamorphosed rocks of the Mount Blanc massif were rapidly pushed up along one of those faults only a few million years ago. The whole area of igneous and metamorphic rock is surrounded by faults, making it what geologists call a “window” – a zone bounded by faults where rocks that are stratigraphically much deeper than the surroundings are visible at the surface.The area has been carved by glaciers over the past few million years, creating the jagged peaks. These glaciers have been retreating rapidly in recent years as the climate warms – the ones you see in this frame used to extend much farther down the slope but they have melted their way back upwards.Glacier melting has been a trigger for avalanches, one of many hazards on this mountain. The peak of summer is the peak for visitors climbing these peaks, and typically up to 50 climbers are actually killed on these slopes during the year.-JBBImage credit: https://flic.kr/p/xnFBv3References:http://bit.ly/2OXUgFJhttp://bit.ly/2OVi1OBhttps://www.bbc.com/news/world-europe-44833398 -- source link

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