How the Green Mountains Were Built
Near Killington, Vermont
The rounded, forested ridges around you are almost unimaginably old, far older than the jagged Rockies or the Alps. Their story begins around five hundred million years ago, when an ancient ocean called the Iapetus lay where New England now sits, and layers of sand, mud, and volcanic rock piled up along the edge of the early North American continent. Then the continents began to close in.
During an event geologists call the Taconic mountain building, roughly four hundred fifty million years ago, chains of volcanic islands and slabs of ocean floor collided with the coast, crumpling and folding those flat layers and squeezing them under tremendous heat and pressure. That heat and pressure cooked ordinary mud and sand into harder metamorphic rock, the shimmering schists, gneisses, and related rocks that form the bones of these hills today. A second great collision, the Acadian mountain building, piled on even more force millions of years later.
The Green Mountains that rose from all this were once towering, perhaps rivaling the Himalayas. What you see now is the deeply worn root of that vanished range, smoothed by hundreds of millions of years of rain, rivers, and grinding ice age glaciers. The soft green profile of Killington is a monument to almost incomprehensible spans of time.
