Although faults are often thought of as forming in rock, they can also form in unconsolidated sediments. The fault in this photograph runs from the upper right to lower left. The fault probably formed as ice melted away from the sides of the esker, causing slumps and faults in the deposit. The sloping layers of sand and gravel behind the group of geologists are outwash deposits on the west side of the Passumpsic Valley esker. The layers dip to the west and formed as glacial meltwater streams carried sediment off of the glacial ice margin into the upper end of Glacial Lake Hitchcock.
Similar deposits occur on the east side of the esker as well.
Varved lake deposit on top of the Passumpsic Valley Esker. This photo was taken directly beneath the Photo 5 site and shows varved lake deposits of silt and silty clay. The varves are cross-cut by faults which formed when ice on either side of the esker melted away, resulting in the partial collapse of the esker. The presence of the varves above the gravels and sands of the esker and outwash indicates that deposition of sediment in the lake continued for many years after the margin of the glacier had retreated northward towards Canada. Photo by Charles V. Cogbill.