Carved in Time, cont'd: Franconia Ridge, NH
With the exception of Bike Week in Myrtle Beach, S.C., today’s eastern North American coastline is relatively passive: no precarious fault lines, no active volcanoes. But this period of geologic calm arrived only recently, and the tumult that preceded it laid down the foundation for New Hampshire’s rugged White Mountains.
Continents tend not to move at highway speeds—more like 10 centimeters per year—but nevertheless they collide in spectacular fashion. Relentless tectonic forces mash them together, fueling volcanic eruptions, driving mountains skyward, and squeezing molten bodies of rock upward through Earth’s crust.
Approximately 360 million years ago, in an event known as the Acadian Orogeny, prehistoric North America collided head-on with Avalonia, a continental mass that included ancient Europe. As the two landmasses fused, the seam joining them became a towering mountain range, its size and height on the scale of today’s Himalayas. These raw, colossal peaks became the foundation for today’s White Mountains.
Over the next hundred million years, the mountains experienced intense volcanism, uplift, and erosion. More collisions followed, culminating in the union of all the world’s landmass into one supercontinent named Pangea. Finally, approximately 170 million years ago in the present-day Pemigewasset Wilderness of New Hampshire’s White Mountains, a massive ringshaped body of lava known as a ring dike rose through the crust and solidified.
The resulting rock, resilient granite porphyry, has resisted glaciation and weathering so dramatically that it now rises 3,000 feet higher than its surroundings: windswept Franconia Ridge.
Today the Appalachian Trail traverses this rocky spine, weaving among frost-shattered outcrops of intrusive rock. An arc of the ring dike runs the length of the five-mile ridge, from Mount Liberty to 5,260-foot Mount Lafayette, and rewards hikers with an unadulterated 360-degree panorama of the White Mountains.
Information: For a classic nine-mile Franconia Ridge loop, take I-93 to Franconia Notch and park at the base of the Old Bridal Path and Falling Waters Trail. Hike up the Falling Waters Trail to the top of Little Haystack Mountain, head north along Franconia Ridge to summit Mounts Lincoln and Lafayette, and turn east onto Old Bridal Path, passing AMC’s Greenleaf Hut on your return to the valley below.
Photo: Jerry Monkman