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A route into your planet

Email|Print| Text size + By Sally Cragin
Globe Correspondent / June 9, 2003

A good traveler has no fixed plans

And is not intent upon arriving

-- LAO TZU

Here in America, the road trip has achieved cultural relevance that has few parallels. We get lost to find ourselves, and after Sept. 11, domestic travel has only increased.

But on your road trips, how often do you look at what you're driving by or even on, rather than what you're driving toward? I don't mean just at the cows and pastures streaming by at 65 miles per hour. I mean at the rocks that were cut to construct our magnificent interstate system, opening new pages in the geological record for scientists.

You don't have to be a scientist to appreciate these slices of the landscape. Just sample the superb and informative guidebook series "Roadside Geology" by Montana's Mountain Press. These books go state by state and provide geologic, geographic, and cultural histories of landscape features. "We look for a manuscript that conveys geology to the non-geologist," says series editor Jennifer Cary. "Teachers often make pretty good authors for these books, because they know where people are when they're just beginning to understand geology."

Granted, New England has some complex geology. Oh, those fortunate folks living in Illinois and Missouri who drive along level roads and see flat layers of sandstone and limestone (remnants of Ordovician seas) for miles and miles. It's not that simple for us, though two primary narratives help explain why New England looks the way it does.

First, there's the debris from glaciation. The rolling hills, the narrow ridges, the round kettle ponds you drive over and by are all the result of ice receding and leaving sand and gravel behind. But scratch the surface, and it gets more complicated. Our bedrock is a mosaic of igneous and metamorphic rock that dates hundreds of millions of years and represents countless geologic events.

Chances are excellent that if you pick up a rock from the bedrock, it might date to the dawn of life on this planet. "Six hundred million years ago an ocean lay where Maine and New England are now," writes D. W. Caldwell in "Roadside Geology of Maine." "The rocks supporting the New England landscape existed then as island archipelagos and as mud on the ocean floor."

Four hundred million years ago (Devonian times), came the Acadian orogeny (which built mountains in what became Maine, and the famous Barre granite of Vermont). During the Mesozoic period, dinosaurs roamed the Connecticut Valley, leaving footprints you can see today.

And just 80,000 years ago (an eye-blink, in geological terms), the Wisconsinian ice age began. Scientists estimate the ice was a quarter-mile high over Worcester, and 400 feet high over Mount Wachusett. When it receded, gravel and rock debris formed "terminal moraines," such as Nantucket, Martha's Vineyard, and Block Island. Thus, a rounded pebble or cobble you pick up might well have come from 15 or 50 miles north. And some rocks, like Fitchburg's Rollstone Boulder, are considerably larger.

The Roadside Geology series is exemplary in a field where there's no intermediary text between the Golden Guides and 10-pound college books. The authorial voice is invariably patient and fascinated. Take James Skehan's laudable "Roadside Geology of Massachusetts." Virtually every community is described so that if you visit, you'll have little difficulty identifying the dominant bedrock. In Canton's Norfolk Basin, if you see pink and gray layered rocks, that's the remnant of an ancient river. If you're in Quincy, you can't miss the famous Quincy granite, which ranges "from light to extra dark and a golden variety called `gold leaf.' "

Social history abounds, especially for areas with local industry. Bradford B. Van Diver goes quarry by quarry in "Roadside Geology of New Hampshire and Vermont" in a Baedeker of bedrock. And Caldwell has written "Roadside Geology of Maine" with the same graceful pedagogy he brought to our outdoor classrooms when I was a geology student of his at Boston University.

All three books are amply illustrated, with photos and diagrams. Glossaries point out the difference between similar-looking rock, and tips on mineral hunting abound. No, minerals don't move, but you do want to protect your eyes, and ask permission if you're on private land.

So far, Mountain Press has published 17 books (one per state for the most part), and New England is nicely taken care of - only Connecticut and Rhode Island are unaccounted for.

"A lot of these books don't get written until the person that's interested in writing it retires," Cary says.

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