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Natural History & Topography

According to the Massachusetts Department of Conservation and Recreation (DCR) Website, “The backbone of [Greylock] was formed from the remnants of an ancient sea bed. According to geologists, between 600 to 450 million years ago, the older Greylock Schist and quartzite formations of the mountain are believed to have been thrust up and folded over on top of the younger limestone and marble of the Hoosac Valley to the east. At one time reaching perhaps 20,000 feet in height, the Greylock massif has been reduced to its present size over eons by constant erosion.”

I have learned to recognize Greylock Schist, which is generally grayish, because there is so much of it in the Reservation. The same for quartzite, a milky white rock which you often see embedded within schist boulders. The limestone quarry at Specialty Minerals down in the valley in Adams mines the limestone below the schist.

Erosion continues, of course, sometimes resulting in landslides. Water plays the biggest part, getting into cracks in schist rock faces or boulders and freezing and thawing, splitting the rock apart. One can see evidence of this all over. In some places the soil depth does not seem to be particularly deep over the underlying rock. I think this has much to do with the great number of trees that topple over in the Reservation. For instance, on the upper part of the Gould Trail on the southeastern face of Mt. Greylock I found and photographed a seemingly healthy tree that had toppled over, roots and all. When I looked at the “footprint” of where it had rooted, it was just about all rock: the roots had had no real chance to dig in deeply and it was no wonder it had toppled over in a strong wind.

Northern Berkshire County can be envisioned as a broad valley running north to south. About 15 miles in length in the same direction, the Greylock State Reservation is something of a big divider between the eastern and western parts of this valley.

This U-shaped valley was scoured out some 18,000 years ago during the last ice age by a kilometer-thick ice sheet that crept southward toward Long Island. When the ice receded it led to a lake covering much of what is now Northern Berkshire.

“As the ice sheet receded northward through the region 14,000 years ago, the Hoosic River valley below the 1,000 ft. elevation contour was filled by Lake Bascom as the glacier dammed up the melt water, preventing its drainage to the northwest. Lake Bascom persisted for about 800 years until it emptied toward the Hudson River in a series of dramatic flood events,” according to a Website on The Natural History of the Berkshires.

This “Wisconsinan” ice sheet overtopped the summit of Greylock, proof of which are the southeast-trending glacial grooves in the rock. I also have found such grooves on Mt. Williams.

About two or three miles to the west of Greylock stands the Taconic range, which runs south-north along the border of Massachusetts and New York up into southern Vermont. To the east, again about two or three miles away, lies the Hoosac Mountain range, which also runs south-north up into southern Vermont. Aligned with Greylock to the north are the Green Mountains of Vermont. All are considered part of the Appalachians. Geographically, Greylock may line up with the Green Mountains, but geologically it is most similar to the Taconics.

Most of the mountains in the Greylock Reservation are clustered in the north and central parts of the park. First, it is worth knowing that the elevation at the Notch Road entrance of the Reservation in North Adams is 1,350 ft.; at the Rockwell Road entrance in Lanesborough, 1,660 ft. Running roughly in a line north-south are Mt. Williams, 2,951 ft., Mt. Fitch, 3,110 ft., Greylock, and Saddleball Mtn., 3,247 ft. A long ridge to the east, running parallel from Mt. Williams almost to Greylock, is Ragged Mtn., 2,528 at its highest point. To the west of Mt. Greylock sits Mt. Prospect, 2,690 ft., about two miles long from its northern base to its southern base. Stony Ledge, 2,560 ft., lies to the south of Mt. Prospect, and boasts the most spectacular view in the entire park.

Two high points of note in the much more level southern part of the park are the popular Rounds Rock, 2,581 ft., with its fine views south toward Pittsfield, and Sugarloaf, 2,034 ft., about a mile west of Rounds Rock.

As you would expect, the drainage off so many mountains throughout the year feeds a multitude of brooks that wind through the Reservation. Not all of them seem to have names. Most flow down rocky beds set in deep ravines. Waterfalls abound. Most of these falls are small, five feet or less, but a few are quite impressive. Among the latter are the Deer Hill Falls on Roaring Brook, Hopper Brook Falls on the March Cataract Trail, and what I call the Silver Fox Falls on the southern tributary of Bassett Brook.

The March Cataract is a huge, eroded rock gash on the west side of Mt. Greylock down which water rushes at times — or so I’m told. I have not yet seen it in action, but I clambered around this treacherous dry slope one summer afternoon. Huge uprooted trees litter parts of it like scattered twigs.

“The southern portion of the Berkshires is drained by the Housatonic River, whose major branches arise on the southwestern flanks of Mt. Greylock and the east-central Berkshire plateau and converge in Pittsfield. The Housatonic River then meanders through the broad valley of the Southern Berkshires flowing south through Connecticut and eventually entering Long Island Sound,” according to the Natural History of the Berkshires Website.

The North Branch of the Hoosic River flows south from Readsboro, Vt. to North Adams. At aptly named River Street, in the flood control chute just west of the Massachusetts Museum of Contemporary Art (MASS MoCA), the North Branch joins the South Branch of the Hoosic, which starts in Lanesborough and flows north. The Hoosic then flows west through Williamstown, turning north into Pownal, Vt. and then northwest around the northernmost point of the Taconic Mountains and through eastern New York, entering the Hudson River at Stillwater, N.Y.

Unsurprisingly, runoff from the Reservation is a major source of the water that feeds the South Branch of the Hoosic. Runoff from the west side of the Reservation feeds the Green River, which flows into the Hoosic in Williamstown. In North Adams, Notch Brook runs off the Reservation north into the city-owned Notch Reservoir. It continues on a northerly path for a mile, creating a spectacular Cascade about two-thirds of a mile in from the end of Marion Avenue, a residential street. From there, Notch Brook drains into the Hoosic near the Northern Berkshire YMCA on the west side of the city.

Finally, visitors to Greylock will see one distinctive rock formation throughout the Reservation: the stone wall. Moss-covered, these have endured long after the farmers who built them in the 18th and 19th centuries passed on. They serve as a reminder that what now might seem a wild, natural place was once substantially cleared and settled — and at times heavily exploited.

Greylock Reservation Project Home

I. Mountain & Park/About the Project

III. Industry & Majesty

IV. On the Reservation

V. What's Here

VI. My Backyard/Road Work/Sources

VII. Road Work Moves Ahead

VIII. Two Great Hikes


View east across the valley toward Mt. Greylock and "the Hopper" from above the Petersburg Pass on the Taconic Range, c. January, 2006.



Huge schist wall hidden high up on the eastern face of Greylock, September 22, 2006.



Quartzite embedded in a schist boulder by the Appalachian Trail on Mt. Williams, May 28, 2006.



A rushing stream and erosion spot on a steep ridge in the Hopper on the west side of the mountain. The stream feeds the south tributary of Money Brook, which flows west between the north slope of Greylock and Mt. Fitch. The erosion and upper stream bed are visible from Haley Farm down in the valley. Christmas, 2006.



Grooves in rock atop Mt. Williams on Appalachian Trail, June 4, 2006.



View of Greylock to the northwest from Cheshire Cobble in the Hoosac Range. Mt. Greylock is in the upper left. Ragged Mountain stretches north in the right side of the photo. The hills in the center of the picture are not part of the Reservation. November 25, 2006.



Hopper Brook flows to the west along the Money Brook Trail, May 26, 2006.



The March Cataract, dry when I visited, August 8, 2006.