How the Champlain Valley Was Made

A slice through the country from the Adirondacks to the Green Mountains, 143 kilometers of it, run backwards a billion years. Drag the timeline, or press play. The lake at the middle is not an accident of where the water went — it is a seam between two collisions, with a tropical sea in between, and the whole chemistry of the basin follows from it.

FROM ABOVE switches to the last chapter seen in plan: the ice sheet coming down this corridor to Long Island and going back up it. That view runs on a real clock rather than by chapter, because the rates are the point — four thousand years going nowhere at the terminal moraine, then four hundred meters (1,300 feet) a year up the Champlain valley. Frames with no dated position under them state as much.

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The modern surface is real: a median profile through USGS 3DEP elevation at latitude 44.45°, the line that runs through Burlington. Everything below that surface, and every stage before the ice left, is drawn — the units, their order and the direction the thrusts move are what the Vermont and New York geological surveys map, and the shape between those control points is illustration. Dates are rounded. Vertical exaggeration is 26×, without which a kilometer of mountain across a hundred and forty of valley would be a scratch.

part of Lake Champlain Hydrodynamics · see also the watershed map, where the calcium layer is this page's last paragraph as a map