HARVARD — It was a decent-sized drain at 2,000 feet long and 200 feet wide.
At least, that was Tophet Chasm in its heyday, 15,000 to 25,000 years ago. It was the exit route for water from a vast, slowly-declining lake.
This unique geological feature, a reminder of our ‘neighborhood’s’ glacially-dominated past, was the subject of Harvard Conservation Trust’s fall Walk and Talk last week.
The Conservation Trust jointly sponsored the tour of the chasm, actually located in Littleton, with the Littleton Conservation Trust.
“Our Walk and Talk series, weather permitting, is intended to get people out onto the land, introduce them to it, get them to see and feel it, and increase their awareness of our conservation land and resources,” said Harvard trustee Rebecca Newsham.
Littleton trustee Art Lazarus, a retired geologist, led the tour of 20 hearty souls hiking the chasm’s environs. He pointed out that the chasm provided drainage for the lake that once covered most of the area we now regard as Boylston, Clinton, Lancaster, Leominster, Princeton and Sterling.
In fact, if you stand at Fruitlands and look west to Mount Wachusett, he said, you can survey the eastern and western boundaries of the vast, barren, frozen glacial-age Lake Nashua.
Harvard, on the other hand, sitting atop what’s known as the Shrewsbury Ridge, would have literally been above it all as the lake’s eastern frontier.
Now the Nashua River is what remains of the lake. And the chasm, to Harvard’s northeast, is what remains of the glacial covering’s retreat north. The waterfall near Prospect Hill, which once marked where the lake actually drained, is gone, too.
Tophet Chasm, with its hemlock groves, is a unique geological feature in the commonwealth, said Lazarus. The other comparable chasm, Purgatory in Sutton, is similar due to the mechanical process of its construction, but it doesn’t have the hemlock.
Tophet, despite its abundant area, isn’t immediately noticeable from developed land. It requires a trek into the glades around Littleton Road near Littleton’s Oak Ridge.
“This is a great time of year for a walk in the woods because of the foliage,” said Newsham. “That and this unusual geological feature was of high interest to us when we decided to make his our first tour of the season.”
The next tour in the series, jointly sponsored with the Bolton Conservation Trust will occur on New Year’s Day, she said. It will be at the Bare Hill Wildlife Sanctuary in Harvard and Bowers Springs in Bolton.
Trekkers will meet at the Bowers Springs parking lot on Flanagan Road. If fortune smiles, they’ll also have cookies du jour to sweeten their tour. Possibly chocolate chip, Newsham said, depending on the preferences of her children