Rapid changes 2005 and 2006
Extremely rapid recession of Vadret da Morteratsch (2001/02: -30.2m; 2002/03: -76.5; 2003/04: +10.3; 2004/05: -22.2) has lead to remarkable developments. In addition, Vadret da Pers and some small mountain glaciers in the vicinity also display impressive effects of the ice recession.
Before the spring of 2005 an ice tunnel had formed on the orographic left side of the Morteratsch glacier snout. Upper entrance, July 2005 (width: several dozens of metres!). Note brownish shear plane in the ice from upper right to lower left.
The tunnel had been melted into the ice by a meltwater stream. The basal morain was exposed. However, in July 2005 no significant amount of water was running through the tunnel any more.
Within the tunnel light can be seen from the lower entrance. In the lower part ice debris from a roof collapse can be seen. Photo July 2005. In the summer of 2006 this whole part of the glacier had already melted away entirely.
Lower entrance of the tunnel. Easy accessibility at the end of a hiking trail made this site a potential danger to tourists: Walking into the tunnel would have been very easy, but obviously roof collapse was a constant possibility.
Comparison photos August 2002 (upper photo) and September 2006. The sign was moved a few metres during the extension of the road. The warning sign is related to the danger of tunnel collapse. Arrows mark a rock outcrop which helps to see the ice recession.
In 2006 a depression formed above the glacier terminus. Tangentially oriented crevasses were reminiscent of "ice cauldrons" above subglacial volcanoes on Vatnajökull, Iceland. The ice was sinking above a subglacial cavity caused by the meltwater stream (QTVR pano, 2.5 MB). Pano wider than 180°, requires scrolling to the right.
View from Diavolezza across Vadret da Pers towards Vadret da Morteratsch (13.9.2006). Arrow 1: new rock outcrop of 2006 (compare next 2 photos); arrow 2: collapse at glacier margin (compare second photo of the last row).
Tele photo view, also from Diavolezza (13.9.2006). Below the rock outcrop ice debris can be seen, and the glacier surface is covered by some moraine from the hole..
New rock outcrop on 14.9.2006 as seen from below. Note the very thin ice cover above the outcrop which most probably will grow in size quickly during the next summers.
New collapse on the glacier margin: "In the presence of a mountain guide and a school party a section of the glacier collapsed, and a hole appeared, about 25x10 metres large." (pers. com. Dr. Max Maisch, Gg, Uni ZH). Photo 14.9.2006. The stream, which is here eroding the basal moraine, disappears in an ice tunnel on the lower left.
Comparison photos from Diavolezza towards Piz Palü (1998 left, 13.9.2006). Most remarkable changes: (1) enlargement of rock outcrop; (2) new middle moraine is forming, others are becoming much more prominent; (3) crevasses increase in size and number as a result of ice thinning.
Remnant glacier near cable car station of Diavolezza (photo 14.9.2006 from the cable car). The small mountain glacier was used, until the early nineties, for summer skiing (see masts on the left). Now it has no more net accumulation: Ablation patterns are evident on the entire glacier surface.
|Photos Jürg Alean|