Here in the Northeast, the advance of the most recent continental ice sheet began about 35,000 years ago. After crossing the St. Lawrence River lowland in Quebec, the glacier advanced across Maine from northwest to southeast. It continued to expand across 400 miles of the Gulf of Maine, reaching its maximum extent along Georges Bank on the outer continental shelf about 25,000 years ago. The earth then abruptly began to warm and the glacier margin started to retreat from the Gulf of Maine about 21,000 years ago, reaching the present position of the Maine coast as early as 18,000 years ago in the west and 17,000 years ago in the east. The recession of the glacier margin in the area of the Ice Age Trail, in contact with the transgressing cold Arctic sea, continued inland to a position a short distance north of the Pineo Ridge Moraine System. Then, at about 15,300 years ago, the glacier margin stabilized or readvanced slightly and deposited the marine deltas and a belt of large, closely spaced moraines of the Pineo Ridge Moraine System. Throughout this zone of glacial retreat, the nature of the landforms demonstrates that the glacier remained internally dynamic. However, the relative scarcity of end moraines and the enormous volume of meltwater-deposited sand and gravel north of the Pineo Ridge Moraine System imply an abrupt onset of warming climate and subsequent rapid meltdown of the ice sheet. This climate change is most probably part of the Bölling climate interval, reflected by rapid atmospheric warming and glacier retreat in both the northern and southern hemispheres, when summer temperatures abruptly rose to those of today. In Maine, the documentation of this event is research in progress.

To read more about Maine in the Ice Age check out these more indepth explanations: Eskers and Deltas, Marine Clay, Salt Marshes and Recent Sea Level Rise, Glacial Retreat, Moraines, Chronology