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The Spring Thaw
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23600 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
3 / 1987 |
1,222 Words |
| Author
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Carl Kurtz
Bodil Kjaer, professor of design at the University of
Maryland, ran her own design and architecture practice for
over twenty years in England and Denmark before joining
academia. Currently she is preparing a proposal for a full-
scale environmental design simulation laboratory for the
United States. |
Winter's grip on the land seems hopelessly long by mid-January. On a bitter cold, windy, gray day the return of spring hardly seems possible. Yet it is winter's duration, its difficulties, and the hardships it imposes that bring to man the hope and promise of spring.
Our first snowfall in the upper Midwestern United States often comes in early November, signaling the start of the winter season. The sun's rays are already striking the earth at an oblique angle. Their power to warm the land has not only diminished, but the day has shortened as the sun moves toward the winter solstice. Temperatures ease downward until daytime highs fail to reach the freezing point. Lakes and marshes freeze first, then the streams, and finally the rivers. New ice is thin and transparent, but as the cold deepens, ice thickens and becomes chalky white and firm enough to support an automobile. Only the occasional riffle from a feeder stream, a rapids, or an underwater spring keeps water from freezing. The land and its watery environs appear to be nearly barren of life. An aura of silence prevails, even the activities of man diminish.
In the northern two tiers of the United States and at high elevations in the mountains south of the Mexican border, winter exerts its icy grip for more than five months. Snowfall may exceed a depth of three meters (about ten feet) while lakes may attain an ice cover of one meter (about three feet) in thickness.
The signs of'Spring are subtle at first, scarcely noticed by all but the most observant. During the relative warmth of midday the cardinal's whistle heralds that change is imminent. He may sing on rare occasions in December. Usually, however, it is after a winter warm spell, (often called the January thaw, even if it occurs in February), that his songS' becomes a regular midday feature. The cardinal' nesting season is still nearly five months away, but his territorial imperative seems to say "plan ahead." By early February, the great horned owl has built its nest and begun to lay a clutch of eggs. With snow storms likely and below-freezing temperatures virtually guaranteed, incubation must be nearly free from interruption. In early March, the eggs have hatched, and the young birds beg for food, requiring almost constant protection by a brooding parent. By mid-March, the pointed hoods of skunk cabbage emerge in a woodland bog to melt the snow with internal heat.
For most of us, the spring does not
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