36 Nebraskaland • December 2020
conditions) exist. Those and other gases remain dissolved in
the water of ponds and wetlands, where they are repeatedly
cycled in and out of plants, animals and microscopic creatures
of many kinds.
The other important factor to understand is that frozen
water can hold less air (those combined gases) than liquid
water can. Have you ever looked closely at ice cubes when
you pull them out of the tray in your freezer? Often, the
outer edges of the cubes are clear, but the center is opaque.
That opaqueness is the result of countless miniscule bubbles
in the middle of each cube. As the water in the tray freezes
from the outside in, that cooling water forces out the air it
can no longer hold in solution. Much of that air gets pushed
toward the center of the cube until it erupts into tiny bubbles,
around which the remaining water freezes.
As I understand it, bubbles of air in frozen lakes and
wetlands arise from the same basic process. Air is forced out
of cooling water and forced into "clusters of air" (bubbles)
as ice forms around it. I see a lot of variation in the size,
depth and number of ice bubbles during my explorations. I
assume the speed with which the water freezes plays a big
role in that, in addition to some other factors. An example of
one of those other factors is when the top of the ice thaws
on a warm day and then refreezes overnight. The air being
squeezed out by freezing water is prevented from being
pushed continually lower by the layer of hard ice below it.
That has to influence how the resulting bubbles look, but I'm
far from smart enough to predict the result.
