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Natural Curiosities

Between Wabasha and Lake City on Highway 61 there are several oxbow lakes. The one at Maple Springs is crystal clear in the winter, and in the summer it is milky white. None of the others do this. What gives?

Larry Zomok

It's likely due to the Maple Springs oxbow's particular combination of vegetation and water chemistry. The lake probably has calcium-rich water seeping into it, says DNR aquatic biologist Robert Burdis. During summer, as aquatic plants photosynthesize, they take carbon dioxide from the water. The loss of carbon dioxide causes calcium to come out of solution and form a whitish material called marl, giving the water its milky appearance.

My brother shot a tom turkey. As it was in its death throes, the two toms traveling with it started to kick and stomp on it. When it died they gobbled over the carcass several times, then seemed to be lost as to what to do until one of the hens traveling with the group called and they went to her. Were the actions of the surviving toms part of the flock mentality of chickens? The dead tom seemed to be the dominant bird in the flock.

R.B. Klein

DNR wildlife research group leader Richard Kimmel says he's seen this behavior a number of times after he's shot a turkey. He says most turkey biologists assume it is related to dominance. When a turkey is injured or killed, the subordinate birds take advantage of the new pecking order.

Over Labor Day weekend, I was driving east when I saw the moon on the horizon. It seemed to be glowing red like an ember. As it continued to rise, it faded to a golden color, and finally cream. What made the moon appear red and orange?

Martha Willand

The moon appeared red to you for the same reason some sunrises and sunsets appear red -- differential filtering of different colors of light by particles in the atmosphere. When the moon is low in the sky, the light from its surface has to travel through more air to reach your eye than when the moon is high in the sky. Especially in late summer in rural areas, the air contains particles that reflect and scatter light. Because long-wavelength light (red and orange) scatters less than short-wavelength light (blue and violet) does, the red and orange light is the most likely to reach your eye.

Where do squirrels go at night to sleep?

Lois and Bob Wallner
St. Paul

According to DNR wildlife educator Jan Welsh, squirrels prefer to sleep in tree cavities, even when they are not raising young. All Minnesota squirrels (flying, red, fox, and gray) will build and use leaf nests if cavities aren't available.

I travel different routes between Hibbing and Duluth a few days a week. Last spring I noticed hundreds of dead pine trees, all in a bunch. There would be a stand of dead trees on one side of the road but not the other. What was killing these trees?

Donna Schoeben

The trees might not have been dead but instead suffering from winter injury, says DNR forest health specialist Mike Albers. When pines are exposed to a lot of sun during winter, their needles may thaw, lose moisture, and die. Albers says the problem was particularly bad last winter due to drought, minimal snow cover, abundant wind and sunshine, and low humidity. De-icing salts can add to the problem as lethal levels of sodium and chloride build up in the needles. Winter stress is especially tough for trees not planted in their ideal environment -- for example, red pines in wet or hardpan soils. Winter damage may make trees more vulnerable to insects and disease, which can eventually do them in.

How many times have glaciers invaded Minnesota? What caused them to recede about 10,000 years ago, leaving all these pristine lakes? Did the world tilt or what?

Ken Ess
Breezy Point

Nobody knows the exact number of times glaciers advanced into Minnesota, says DNR geologist Heather Arends, because the glaciers themselves removed older glacial sediment from the geologic record. During the past 2 million years, there is evidence of up to 30 cold periods separated by warm periods. What drove these past climate changes is still being studied. Astronomical factors, such as changes in Earth's tilt, orbit, and solar output, can cause periods of warm and cool climates. However, factors such as ocean currents, atmospheric currents and chemistry, and amount of atmospheric dust appear to have also played a role in the advance and decline of the last glaciation.


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