Worcester County was once under 1,000 feet of ice.
COLUMN: ALBERT B. SOUTHWICK
There has been much discussion of late about the melting glaciers of the globe and what that portends for human settlements near sea level. There are 672,000 cubic miles of water locked up in the Greenland ice sheet, and 6 million cubic miles in Antarctica. If all that were melted and added to the oceans, the sea level would rise by 140 feet and many of the world's coastal cities, including New York and Boston, would be submerged.
I don't want to get into the controversy over whether human activity is causing global warming - but I do note that ice ages and warm spells come and go, regardless of what or who is living on the planet at the time. In the last 2.5 million years, there have been at least five major episodes of glaciation and melting, the last one only 10,000 to 20,000 years ago.
That one was sometimes called the Wisconsin glaciation because evidence of its southernmost journey is shown by the remains of a smashed spruce forest at a place called Two Creeks, Wis. Tests revealed that the glacier killed the forest about 11,000 years ago at the peak of the Ice Age.
After that came the great melt over the next 3,000 or so years as the sprawling ice pack retreated northward.
Eleven thousand years is not a long time in geological terms. I like to try to visualize how this region that we call Worcester County looked in those distant years. We sure wouldn't recognize it. Imagine flying in a helicopter over this area in, say, 9056 B.C.
We would look over a white expanse of ice stretching from horizon to horizon. We would see nothing familiar. Worcester's seven hills and Asnebumskit would be 1,000 feet or more below the surface of the ice pack. If we could land our helicopter in what is now Princeton, the summit of Mount Wachusett would be hundreds of feet down. Mount Monadnock and the rest of the White Mountain range would be buried under millions of tons of ice grinding away at the granite spine of New England and depositing broken rocks and stones all the way to New Jersey.
Canada would be one vast sheet of ice. So would Siberia and much of northern Europe, including the British Isles. Another ice cap would develop from Antarctica and spread northward as far as New Zealand. Curiously, the Arctic Ocean would not be frozen over. It would be virtually landlocked, shrinking every year and producing the vast clouds of moisture that would rise into the atmosphere and produce the endless snows that created the ice cap in the first place.
To continue with our thought experiment, let's suppose that we flew our helicopter south over the vast ice pack. We would find Manhattan icebound but Staten Island would lie just beyond the glacial limit. We would fly west over New Jersey along the "terminal moraine" where the glacier finally came to a halt, depositing its load of stone, gravel, sand and debris. From there to Montana we could travel along the circuitous southern edge of the glacier and gaze at the "great palisade of green and white ice many hundreds of feet high and stretching to the horizon east and west."
In a few thousand years, that massive sheet of ice had changed the northern part of our continent forever. The billions of tons of frozen water had warped the Earth's crust and scoured new paths for the immense streams of water that would begin to refill the depleted oceans when the great melt got under way. Just as the glaciation had taken thousands of years, the melting took thousands more. Gradually, over the centuries, the shrinking ice pack revealed new land contours, new lakes, new rivers and different mountain terrain. The glacier, traveling ponderously over the land a few feet a year had ground millions of tons of granite from the White Mountains and deposited them along with other debris the length and breadth of New England - where they have plagued farmers for the past 300 years.
The great glacier shaped the land in many different ways. Thousands of lakes were carved into the terrain as the ice gouged the soil and gravel down to bedrock in many places. Lake Quinsigamond and Lake Champlain are examples. Rivers were dammed and diverted into new channels. As the ice sheet melted, it deposited loads of gravel and dirt into symmetrical "drumlins." One of the prettiest of those was located behind the David Prouty High School in Spencer until it was leveled a few years ago. Dean Homer P. Little of Clark University used to take his geology class out to look at it every year
Some of the most interesting post-glacial phenomena can be seen on Cape Cod and off the Massachusetts coast. Long Island, Block Island, Martha's Vineyard, Nantucket and much of the Cape are remnants of the terminal moraine, where the vast ice sheet finally stalled and dropped its immense load of sand.
The ice sheet, which was up to 2 miles thick, had depressed the Earth's crust in places, forcing the underlying magma into unusual patterns. Geologists believe that the crust is gradually springing back and that Hudson's Bay, for example, eventually may become dry land.
The long melting process would have been something to observe. As the relatively warm rains and sunlight gradually pierced the fissures in the ice, there must have been almost continuous crackling and grinding sounds echoing over the bleak ice sheet. As it slowly retreated across New York and the Midwest, it left behind the Great Lakes, plus an even larger body of water that covered most of Manitoba and northern Minnesota. The Great Salt Lake of Utah is a remnant of those distant times.
Today, according to the geologists and climatologists, the mammoth ice packs are still shrinking. Greenland and Antarctica are the main remnants, although there still are many mountain glaciers in Alaska, Canada and Europe.
What will the future bring? We'll have a better answer to that question in 10,000 or 20,000 years.
Albert B. Southwick's column appears regularly in the Sunday Telegram.
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|Publication:||Telegram & Gazette (Worcester, MA)|
|Date:||Nov 4, 2007|
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