While alpine glaciers are a defining feature of the Cascade Range as a whole, this is especially true of the North Cascades. The stratovolcanoes (Mount Baker and Glacier Peak) are the most obviously glaciated peaks and have the largest glaciers, but many of the smaller, nonvolcanic peaks are glaciated as well. For example, the portion of the Cascades north of Snoqualmie Pass (roughly the North Cascades as defined in this article) These glaciers all retreated from 1900-1950. From 1950-1975 many but not all North Cascades glaciers advanced. Since 1975 retreat has become more rapid with all 107 glaciers monitored retreating by 1992. 2015 was an especially damaging year for Cascadian Glaciers, an estimated mass loss of five to ten percent, the single greatest loss in over 50 years. There are approximately 700 glaciers in the range, though some have already disappeared. Since a brief advancing period in the 1950s, most of these glaciers have been retreating. This is a serious concern to water managers in the region, as the glaciers (and the winter snowpack) form a large reservoir of water. As snow and ice melts in the summer, the resulting meltwater compensates for the seasonal decrease in precipitation. As glaciers retreat they will provide less summer runoff.