The landscape of the Prosper Valley was partly shaped by events more recent than the movement of continental plates - if you can call 18,000 years ago more recent! This was the last period of glaciation in North America, when Vermont lay under an ice sheet over a mile thick. The movement of this glacier was a powerful force that pulled up rocks in its slow movement forward, which were heavily compacted and churned over time, and then deposited back on the landscape as the glaciers melted and retreated. The resulting mix of different sized stones left on the land is called glacial till. This surficial geology is the reason behind the rocky soils well known to Valley farmers and gardeners. It is also the reason behind Vermont’s familiar stone walls. As early settlers tilled and plowed the land, they used the rocks they pulled to create walls to contain their sheep herds.
But glacial till isn’t the only material left behind in the wake of the glaciers. During the glacial retreat, ice blocked pathways of flowing water, causing lakes to form in places. At one point, the glacier hovered near Middletown, Connecticut long enough to create Glacial Lake Hitchcock, which covered a large portion of southern Vermont. Gravel and sand were deposited in places where deltas formed between glacial rivers and lakes, and finer sediments were dropped in the slow waters of the lakes. One formation of sand as it was deposited by glacier meltwater is a kame terrace. Kame terraces are visible in the Valley, such as beneath an abandoned section of old State Route 12. When the earliest settlers created this part of the road they probably chose its location based on the ease of constructing on a flat, sandy expanse. The bursting of the dam holding the waters of the Lake is associated with the formation of the Quechee Gorge.
Surficial Geology Map of the Prosper Valley
Classic rocky Vermont soils
Gilbert Hill in Woodstock