Archive - Bubble Columns in River Ice

April 08, 2018


Each Sunday we present a notable item from our archives. This EPOD was originally published April 09, 2012.

Photographer: Roger Benoit 
Summary Authors: Roger Benoit; Jim Foster

This picture showing curious bubbles on the frozen Aar River was taken this past winter near Umiken, Aargau, Switzerland. It had been bitterly cold for several days before when the photo was snapped. It's not known exactly how these bubbles formed, but it's likely they were released from the riverbed and became trapped under a thin layer of ice. As deeper layers of water froze perhaps additional bubbles became trapped further down in the ice -- closer to the riverbed. Such a mechanism would also explain the flat appearance of individual inclusions. Typically, the faster the freezing rate, the greater the number and the size of the bubbles. In this case, the arrival of very cold air substantially increased the freezing rate. Note that the inside of one of the near-surface bubbles has been exposed (at right center). Photo taken on February 12, 2012.

Photo Details: Camera: Canon EOS 550D; Lens: EF300mm f/4L IS USM6 IS; Focal Length: 300mm; F Number: f/4; Aperture Value: 4; Exposure Time: 1/125; Shutter Speed: 7; ISO: 200. A circular polarizer was used to increase the contrast of the photo.