One of my faculty colleagues, Michael Runtz, took this photo
(right) of ice bubbles in Cranberry Lake in Ontario. How did the
bubbles form in this amazing fashion? Without any scale
reference or indication of the depth of the lake I cannot tell
for certain, but I have seen similar bubbles frozen in ponds
where I grew up in upstate New York. In freshwater ponds and
lakes, the biological activity of microbes in the sediments on
the lake floor produces bubbles of gas, usually methane or
carbon dioxide. In winter this activity is slow, but it is still
present. The gas bubbles rise to the frozen surface of the lake,
becoming trapped there. The following night, another layer of
ice forms beneath the bubble, so it is encased in ice. This
leads to the flattened shape you see. The picture is a frozen
daily record of the gas emissions. To continue reading this
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