Pressure Ridge on Lake Sebago

March 26, 2015

Ice pressure ridge  011815 3a

Pressure ridge and pier Sebago 012815

Photographer: John Stetson
Summary Author: John Stetson

Shown above are two views of a pressure ridge just offshore of ice covered Sebago Lake in Maine. At top is a ground level view - a red ice fishing hut is in the background. The bottom photo was taken from a kite-mounted camera flying at an altitude of about 70 ft (22 m). Ridges such as this result when ice expands, most often after a day or two of relatively warm weather. When ice on Sebago Lake expands the lake moans, and when the ice releases pressure it can feel like an earthquake; foundations of nearby houses actually shake. Ice can have stiffness similar to that of hardwood bent along the grain and flexural strength comparable to that of the white pines that surround the lake. Photos taken January 18, 2015.

Photo details: Top - Camera Model: NIKON D700; Lens: AF Nikkor 50mm f/1.8D; Focal Length: 50.0mm (35mm equivalent: 50mm); Aperture: ƒ/10.0; Exposure Time: 0.010 s (1/100); ISO equiv: 200;
Software: Adobe Photoshop CS4 Macintosh. Bottom - same except: Focal Length: 2.5mm (35mm equivalent: 16mm); Aperture: ƒ/2.8; Exposure Time: 0.0008 s (1/1192); ISO equiv: 100.