×

The Potholes: Not ‘glacial,’ still special

  • Potholes cascade into each other on the Deerfield River in Shelburne Falls are a popular tourist attraction. Recorder Staff/Paul Franz

  • Potholes cascade into each other on the Deerfield River in Shelburne Falls are a popular tourist attraction. Recorder Staff/Paul Franz

  • An overall view of the potholes on the Deerfield River in Shelburne Falls. Recorder Staff/Paul Franz

  • A pothole at the glacial potholes on the Deerfield River in Shelburne Falls. Recorder Staff/Paul Franz

  • Colorful striations at the glacial potholes on the Deerfield River in Shelburne Falls. Recorder Staff/Paul Franz

  • The glacial potholes on the Deerfield River in Shelburne Falls. Recorder Staff/Paul Franz

  • Water flows over the potholes on the Deerfield River in Shelburne Falls. Recorder Staff/Paul Franz

  • Potholes cascade into each other on the Deerfield River in Shelburne Falls are a popular tourist attraction. Recorder Staff/Paul Franz

  • Two potholes carved by the flow of water at the potholes on the Deerfield River in Shelburne Falls. Recorder Staff/Paul Franz

  • Geologist Richard D. Little. Recorder Staff/Andy Castillo Recorder Staff

  • LITTLE



Recorder Staff
Thursday, January 26, 2017

By DIANE BRONCACCIO

Recorder Staff

SHELBURNE FALLS — One of the first things geologist Richard D. Little must do in his many talks about Shelburne Falls’ Glacial Potholes is dispel the notion that the stunning, varieagated rocks, with their chiseled-out “potholes,” were formed by glaciers.

“The rocks are just beautiful, with their light and dark banding,” he said. “That is because of the collision of continents — the pangaea,” he explains.

The pangaea was the collision of continents at least 300 million years ago.

If anything, the Potholes should be named “the post-Glacial Potholes,” says the retired Greenfield Community College professor and author of “Dinosaurs, Dunes and Drifting Continents: The Geohistory of the Connecticut Valley.”

The Shelburne Falls Glacial Potholes, he says, couldn’t have formed until Lake Hitchcock, which was formed by the damming of glacial waters, receded about 14,000 years ago.

“The rocks are just beautiful — beautiful light and dark banding — that is because of the (Pangea) collision,” he said.

“I tell people that this is the best place in the world to study geology — and not just in Shelburne Falls,” says Little, whose talks on the Glacial Potholes still draw huge crowds. “Look at all the metamorphic rocks we have in the hills, and then you have the glacial features and the potholes. And then you come to the Connecticut Valley itself and you have the dinosaur footprints, and old Lake Hitchcock and the lava flow — where Poet’s Seat is — it’s built on a lava flow 200 million years ago — it’s spectacular. It’s absolutely spectacular.”

River potholes are not uncommon, says Little, but Shelburne Falls’ potholes are “extra beautiful, because they’re well-exposed, they’re deep and they’re in that gneiss, which is so pretty.”

“But yeah — potholes are common. You could say that potholes are as common in our rivers as they are in our roadways,” he says.

“As plates come together, you have enormous pressures that squeeze things. The rock that’s there was actually formed about 10 miles underground, in the center of the earth’s crust. It’s only been erosion that’s exposed those really deep rocks. so when you see those layers that are light and dark, they’re due to the minerals that just kind of flowed under pressure. They didn’t melt, but they just squeezed and recrystalized and moved relative to one another. And the light and the dark minerals tend to separate out, under those conditions.”

The largest of the so-called Shelburne Falls potholes is not a pothole at all, according to Little. Instead, it’s a “plunge pool” at the base of a waterfall, formed simply by water pressure.

“A pothole has a level, circular opening to the hole, caused by a current going across the crack, with pebbles that fall into the crack and twirl, acting like a drill when water is going across,” Little explained. “So — as opposed to water falling — this is just water going laterally across the rocky surface. The pothole has a level rim, while the plunge pool has the waterfall. These are two different processes that form these holes.”

One distinction to the Shelburne Falls potholes is that they are made of gneiss — pressurized granite in which the light and dark speckles have separated.

“That rock used to be a granite, and granites are speckled,” he explained. “When you have the collisions that made pangaea, that was a zone of volcanoes there in Shelburne Falls, but they’re gone now. Next thing is the collision. With the collision, comes the light and dark speckles in the granite. They’re called gneisses. They’re just beautiful. So they are indeed nice. That’s one of our geology jokes: “Is this gneiss? Yes indeed, it’s nice,” he says.

“I think the Shelburne Falls potholes are very special because they’re in that beautiful gneiss rock and there’s a rather wide expanse of them.”

Some have estimated there are 50 potholes. Little says he doesn’t know the exact number, but 50 sounds about right.

“They’re fairly large potholes,” he said. “You can hop into them and stick your head out,” he said, recounting the times when people could go down a stone walkway and get close to the rock formations.

But access down to the Glacial Potholes from an observation area has been gated-off because some people have gotten injured, and the town has liability concerns.

“It’s so sad that, as a geologist, I used to lead field trips there all the time, and people used to come from all over. But they can’t go there anymore,” he remarked.

Little said he wishes someone could resolve the liability risk issue.

“I’m so fortunate to end up here,” said Little, who has worked as a geologist all over the country. “I’ve had a chance to teach for almost 50 years now. I was just lucky to get my job in Greenfield.”

Little believes the region’s “spectacular” geology should be the base for a huge tourism industry.

“If people don’t realize what they have, it gets lost,” he said. “So it needs to be appreciated.”