Hogback Mountain

When we look out on the wilderness, we imagine that it has always been this way, untouched and unaltered. This, however, is a massive misconception. The land on which we stand has been changed beyond recognition over Earth’s history.

For those who are interested, and know what to look for, the evidence of that change is readily available. Take Hogback Mountain, in southern Vermont, for example. For as long as anyone can remember, its 2,409-foot-high peak has been a landmark in these parts.

Most who look upon it assume that it has always stood where it does, unchanged for millennia. The truth is, Hogback Mountain is, like many other of the other peaks that stand nearby, a movable feast — it has, over nearly half a billion years, shifted its location thousands of miles, and even the stones of which it is made have changed over time.

On Nov. 9, Roger Haydock, a self-taught amateur geologist and former staff member of the PBS series “Nova,” will present a slide show and walk, “A Half-Billion Years of Hogback History,” at the Southern Vermont Natural History Museum, located at the Hogback Mountain Conservation Area in Marlboro, Vt. He will focus on the particular history of this mountain and illustrate the metamorphoses it has encountered over the eons.

“Hogback Mountain is comprised primarily of metamorphic rock, which is present throughout most of southern Vermont,” Haydock said. “In its composition, it is related to the rock in the Taconic Mountains, which are in the western part of the state. When the Taconic range was shoved westward 460 million years ago, most of them ended up in western Vermont or eastern New York state.

“Some of them made it all the way, but there were also some stragglers. Hogback is one of those, along with Mount Snow and Haystack Mountain.”

For those of us who aren’t familiar with geology, Haydock explained exactly what metamorphic rock is, and how it is formed.

“Metamorphic rock is a substance that has changed from something else, which could either be sedimentary or igneous, before it has been cooked and crushed,” he said. “An example of this would be limestone, which is a sedimentary rock. Once it’s crystallized, however, it turns into marble.”

Haydock said that the talk will focus not only on southern Vermont but will cover New England geology in general. For those interested in fossils in this area, however, they’re likely to be disappointed.

“Whatever fossils were originally there were cooked and depressed away,” he said. “Where you do find fossils, however, would be in central Massachusetts, where the rocks are much younger — only 200 million years old. They boast some of the best dinosaur footprints to be found anywhere in the world.”

Haydock said the talk will also cover the ice ages, which also altered the geography, as well as the nature of the soil itself.

“The ice ages came in several million years ago,” he said. “Only 200,000 years ago, all of New England, except for Martha’s Vineyard, Nantucket and part of Cape Cod, was completely covered in ice. This is one reason farming hasn’t been too successful in this region. The glaciers took so much of our soil, and what we were mainly left with is sand.

“The metamorphic rock itself was originally clay, which turned into schist (medium-grade metaphoric rock formed from mudstone or shale). When that was ground down, it turned back into clay, which is a little better for farming. That’s why eastern Long Island has such good soil.”

Haydock also pointed out that the continents have moved significantly over the last 400 million years. Back then, all of North America was south of the equator, and Vermont and New Hampshire occupied what is now Brazil.

“It’s really fascinating to see the history of this place written in the rocks,” he said. “I think people will come away with a new appreciation of the history of this planet.”

Roger Haydock presents “A Half-Billion Years of Hogback History” Saturday, Nov. 9, from 9 a.m. to noon, at the Southern Vermont Natural History Museum, 7599 VT Route 9 East. For more information, call 802-464-0048 or visit vermontmuseum.org.