Reviewing some old photos, I noticed a remarkable image from the Lloyd Anderson collection, taken on April 14, 1940 during an attempt to climb Forbidden Peak in the North Cascades. A sharp eye reveals that in 1940, Moraine Lake (below the Inspiration Glacier) largely did not exist.
In the photos above, the 'X' in each photo indicates roughly the same location in the landscape. To my eye, the area marked "Ice Margin" in the left panel is a snow-covered glacier snout. I added pointers to what I think is the approximate edge of the ice.
The other two pictures are from my collection, taken from the summit of Forbidden Peak.
The April snow cover in the 1940 photo makes it harder to tell where the ice extends, but I'm pretty sure the zone marked by "Ice Margin" was glacier covered at that time.
I'm unaware of a more dramatic example of the lengthwise recession of a glacier in the North Cascades in the past century.
To my eye, there is too much snow cover in the 1940 photo to tell the full extent of ice. I recall seeing some historical photos with ice in Moraine Lake. I wonder if aerial photos could shed some light on the extent of ice between 1940 and 1979.
Also I see big changes in ice extent between the 1979 and 1996 photos but there appears to be limited changes in ice extent between the 1996 and 2019 photos.
I wonder if aerial photos could shed some light on the extent of ice between 1940 and 1979.
I've done quite a bit of searching for USFS aerial photos at the National Archives, some going back to 1934. They were taken from a relatively low flying plane on clear days. It must have been quite a logistical problem to get coverage of an area. But the point is, it was a hard thing to do and they focused on timbered areas because the goal was planning the "cut". I don't think there's a great chance that this area would have been photographed in the periodic aerial photo surveys.
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