Ice Age left its fingerprints all over the scene

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The other day the forecast near my home included winds up to 50 mph. That's a strong wind, to be sure, but not something I'd write home about. One forecaster I heard, however, presented the news in a shrill voice, as if we might have to stay in the basement all day. I considered calling his station and explaining that, when I was a small child, we walked to school in winds of 50 mph (and back) without a second thought.

But I suppose every profession must be forgiven certain types of errors. Geologists have ours, I know. So a bit of hype from weather folks is better than their being so relaxed we don't get the message when a hurricane is arriving.

But the greatest windstorms sweeping over the U.S. in our era are nothing compared to those that created the landscapes some of us live on. For wind in times past did not just move through the air, it shaped the solid Earth as well.

When I look out of my windows, I see dramatic evidence of Ice Age windstorms. That's because I live and work in a veritable sea of dune-shaped hills made of windblown silt. Storms and weather catastrophes, with great shifts of regional and global temperatures, are the threads woven together and draped over the landscape that grace my home.

Driving through my part of the world is a bit like a seagoing journey. The road goes up and down over the hills, as dune-like mounds are popping up and then falling away behind the car all around. Think of driving through a sea of sand dunes and you'll have part of the picture. Replace the sand grains themselves with finer silt, and you've got it nailed. Even geologists are in awe of just how much silt was in the air when the hills formed -- doubtlessly going a good way toward gagging every animal around.

The soils are of the most fertile types in the world, and create regions known as "breadbaskets" for their production of cereal grains. The conundrum shows how nature works -- old problems like choking windstorms can lead an epoch later to abundant blessings of plant growth even in areas not known for gentle winters or mild summers.

Silt is a prime ingredient in this soil type known as loess (a word with German origins, which Americans can get away with pronouncing as if it rhymes with "dose"). Loess covers a good bit of the inland Northwest, where I live, but also the Great Plains and the upper Midwest. It forms a blanket of soil in eastern Europe and Russia, and also inland China. In all those locations -- except my own -- the blanket of loess makes flat plains, not undulating hills. We don't know for sure, but the hills around my house may have meant the wind direction here in the inland Northwest varied a lot, while in those other places it was more constant.

One thing is sure: thick blankets of loess are indirect geologic evidence of the Ice Age, that geologically recent epoch when global climate was so very different. The reason for that is that great windstorms create loess, and major expanses of ice on Earth help shape weather systems that generate such windstorms.

Here's one way to think about it: Greenland or Antarctica shape the weather around them because, especially in the summer, the seas near them are relatively warm (relatively!) but ice and snow -- of necessity -- are always below 32. Winds, as you may recall from some Earth Science lecture, are often the result of differences in temperature. So it makes sense that winds near the glaciers that once covered Canada in the Ice Age were fierce indeed, just as gales near Greenland and Antarctica are always in danger of springing up today.

Just a couple of centuries ago people had no inkling that the Ice Age and its dramatic effects on the world were all around to be seen. Today, if the forecast near you doesn't call for much in particular, it's a good day to get out and look at the evidence of past climates all around us.

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