undifferentiated rock units

Paleontology and geology

During the Devonian, a phase of mountain building (the Acadian Orogeny) occurred in Vermont and the surrounding region. This tectonic activity deformed and metamorphosed older rocks and caused the intrusion of molten igneous material into the crust beneath the state. These intrusions have been interpreted as the magma chambers of a series of volcanoes that have long since eroded away.