Field Notes—

An Abiding Hitchhiker

In Sandy Hook

By Curtiss Clark

There is a hitchhiker standing off to the side of Route 34 in Sandy Hook who has been waiting for a ride for the last 13,000 years.

It was dropped off on a bedrock knoll on state land about 50 feet northeast of the rock cut near Mill Road by the Laurentide Ice Sheet, which had come down from the Laurentian Mountains of Quebec at the time to build Long Island, Block Island, Martha’s Vineyard, Nantucket, and Cape Cod.

Newtown, and all of New England for that matter, is thickly populated with these ice age travelers — boulders torn from the bedrock by a crush of ice a mile thick and pushed, carried, or rolled southward until the ice retreated north about 13,000 years ago, leaving them without a ride.

The Ice Age in Connecticut began two or three million years ago, and geologists believe there have been several glacial advances and retreats in that time. Because 13,000 years represents just a quick pit stop in geologic time, some experts assert we are still in the Ice Age, global warming notwithstanding. In a few thousand years, the next glacial advance may once again sweep the surface of New England southward so our stranded friend on Route 34 can continue on its way again.

I came across this particular boulder a few weeks ago when I was looking for something else — a grove of American chestnut trees that the late Walter Sherry had shown to me about 25 years ago. I never found the trees. They were probably claimed by blight ten or 15 years ago. But this light colored rock stood out from the dark dapple of the surrounding trees and caught my attention. It’s about 8 feet by 8 feet by 10 feet, and it dominates the woodland scene. I’ve seen these large solitary boulders in the woods before, sitting with smug inscrutability, daring anyone to decipher their story. With this rock, I wanted to take the dare.

Fortunately, my brother, Russ, was due in town for a family Fourth of July get-together. Russ is an amateur golfer, amateur genealogist, amateur teller of bad jokes, and professional rock reader. He’s a geology professor at a small college in Michigan. He’s also a Connecticut native, and he knows the rocks here.

So when he arrived in Connecticut, I didn’t have to do much persuading to get him to take a break from the attic-cleaning detail at my mother’s house to come take a look at the boulder. After successfully negotiating our way across the truck traffic on Route 34, around a lush patch of poison ivy, and over a vitals-tightening barbed wire fence, we scrambled up over the knoll to the rock. He began his narrative, and I took notes.

According to Dr Clark, it’s a granite pegmatite boulder liberally laced with feldspar and quartz crystals and muscovite mica. (Muscovite mica has also been known as muscovy glass or eisenglass, and its was used to make small windows for furnace burners because it doesn’t melt.) The boulder’s whitish look comes from large feldspar crystals throughout.

I was hoping that my brother would tell me that this rock was an erratic boulder that had ridden the glacier down from Canada, but that angle of this story was dashed, quite literally, on the rocks below us. Surveying the area, he said that the ice sheet had left two calling cards in this place: the boulder and the exposed granite gneiss bedrock at the crest of the knoll. The ice had smoothed the surface of the underlying rock. And in the rock cut down by the road, there was an intrusion made of the same stuff as the boulder — pegmatite.

True erratics are rounded after being tumbled for great distances beneath the ice, and their composition is often distinct from the local rocks. (Plymouth Rock is an erratic — a true pilgrim. It was headed to Cape Cod when it settled in Plymouth. The Mayflower pilgrims were headed from Cape Cod when they settled in Plymouth. Their meeting made history.) The boulder off Route 34 is still angular, suggesting that it broke off from the bedrock nearby — maybe Jeremiah Road, or Southbury, or Bridgewater.

But this turns out to be a story of ice and fire. Pegmatite is igneous rock normally composed of granite riddled with large crystals that formed quickly in watery magma far below the surface of the earth.

Long before it hitched a ride with the Laurentide Ice Sheet, this boulder started its journey about five to ten miles below the surface of the earth. If you think its 13,000-year wait down on Route 34 is tedious, consider the 400 million to one billion years it had to wait for erosion to wear away five to ten miles of the earth’s crust for its debut on the surface.

During that time, veins of quartz crystals cut through some of the fractures and weak spots in the granite. Russ spotted some small examples of “graphic granite” on the surface of this boulder. This occurs when small rods of darker quartz crystals intrude on the lighter feldspar creating the effect of cuneiform writing. Jewelers will often use the cryptic script of graphic granite as beautiful and unusual gemstones in pendants or ornaments.

The unreadable writing tells only of deep, deep mystery. Despite all my brother’s insights into the origins of this rock, its smug inscrutability ultimately prevails. We don’t know exactly where it came from. We don’t know exactly where it’s going. In the life of this rock, my existence, my brother’s existence, perhaps even the existence of humankind, is passing by its upturned thumb at the speed of light.