March 10, 2012
The Taconnaz Glacier flows from 4300 m to 2000 m down the west side of Mont Blanc, from the Dôme du Goûter toward the Chamonix Valley. This glacier is best known for the large avalanches that are generated by the break off of large serac ice blocks from a wide ice cliff at 3300 m during the winter, blue arrows (Le Meur and Vincent, 2006). The ice blocks have been devastating to inhabited areas of the Chamonix valley as recently as 1999. A comparison of 2004 and 2009 imagery in Google Earth indicates that the main terminus (A) has retreated 200 meters in five years. The orange line is the 2004 margin and 2009 is the red line. Taconnaz is two glaciers south of Mer de Glace, which retreated 500 m from 1994-2008, and several glaciers south of Glacier d’Argentiere, which retreated 400m from 2000-2010. There has also been a large retreat in the vicinity of Point B which is where a secondary terminus used to be connected to the main valley glacier. This retreat indicates that above the terminus there is a reduction in the volume of ice heading down valley. This suggest retreat will continue.
The avalanche hazard has prompted construction of avalanche defenses that are well documented in photographs, such as the one below. This site on Mont Blanc glaciers also has nice images of the terminus glacier from 2010 indicating a much more robust terminus than Mer de Glace, based on the crevassing and glacier thickness. The avalanche protection worked in 2006 slowing an April avalanche.