Aletsch Glacier, shown above carving through the Bernese Alps of Switzerland, is nearly 14 mi (23 km) in length making it the longest glacier in the entire Alps mountain system. Image © Renata Hari, with permission.
Aletsch Glacier is currently in retreat as are nearly all glaciers in the Alps. The dark narrow bands within the glacial ice are medial moraines, formed when individual valley glaciers merged. These moraines extend many miles downstream. The wavy features at bottom are possibly ogives — spacing between the wave crests related to the ice flow over a given season. To give scale to the immensity of this glacier note the hikers at bottom center. Photo taken in late summer of 2013.