Banff National Park has numerous large glaciers and icefields, 100 of which can be observed from the Icefields Parkway. Small cirque glaciers are fairly common in the Main Ranges, situated in depressions on the side of many mountains. As with the majority of mountain glaciers around the world, the glaciers in Banff are retreating. While Peyto Glacier is one of the longest continuously studied glaciers in the world, with research extending back to the 1970s, most of the glaciers of the Canadian Rockies have only been scientifically evaluated since the late 1990s. Glaciologists are now researching the glaciers in the park more thoroughly, and have been analyzing the impact that reduced glacier ice may have on water supplies to streams and rivers. Estimates are that 150 glaciers disappeared in the Canadian Rockies (areas both inside and outside Banff National Park) between the years 1920 and 1985. Another 150 glaciers disappeared between 1985 and 2005, indicating that the retreat and disappearance of glaciers is accelerating. In Banff National Park alone, in 1985 there were 365 glaciers but by 2005, 29 glaciers had disappeared. The total glaciated area dropped from in that time period.