Connecticut River Valley

All good things must come to an end—even when that good thing is the enormous, ancient supercontinent Pangea. It lasted 100 million years, but unrelenting plate tectonics ultimately split Pangea apart 205 million years ago. But like a costume torn in a wrestling match, sometimes the continental fabric does not break along its original seams; instead it splits apart, or rifts, in slightly different, unexpected places. And across New England exists a scar where Pangea initially came apart: the Connecticut River Valley.

Like many break-ups, Pangea’s parting was anything but smooth. As the heft of present-day North America tore away from the supercontinent, the land fractured extensively and began to spread apart. Earthquakes rumbled. Hollywood-scale lava flows spilled forth in New Hampshire, Vermont, Massachusetts, and Connecticut. Ocean water poured into the opening fissure, depositing thousands of feet of sediment and forming a nascent sea. But then the geologic commotion eased, and the earth stopped splitting in the future Connecticut River Valley. Instead, another more permanent rift opened farther east, defining the basic New England coastline of today and giving birth to the Atlantic Ocean.

The present-day Connecticut River Valley bears evidence of its past turmoil. In lieu of an ocean, the Connecticut River now occupies the broad vale, followed by bands of cooled lava from New Hampshire to Connecticut. Near Holyoke, Mass., the summit of Mount Tom crowns a pronounced ridgeline of tilted lava beds, offering far-reaching views of this broad continental tear.

Dinosaurs once witnessed the geologic mayhem here; their tracks abound in the valley below. In several locations, three-toed prints likely laid down by predatory Dilophosaurus meander along the river’s expansive banks.

Information: To visit dinosaur prints, take Route 5 south from I-91 toward Holyoke for 5 miles. The entrance to Dinosaur Footprints Reservation (Trustees of Reservations) will appear on the left. From there, head over to Mount Tom State Reservation, where 20-plus miles of trail meander above the Connecticut River; come fall, lava appears to resurge as the changing leaves flare red.

Resources: Massachusetts Trail Guide (AMC Books); Mount Tom State Reservation, 413-534-1186, www.mass.gov/dcr; Dinosaur Footprints, 413-684-0148, www.thetrustees.org.