About 25,000 years ago, New Hampshire and much of the northern United States and Canada were covered by a thick glacier known as the Laurentide Ice Sheet. As this glacier began to recede about 12,000 years ago, glacial lakes formed at the edge of the retreating ice sheet. In New Hampshire, there were several glacial lakes that changed in size and location as the glacier continued to recede. The glacial lake that existed in this part of the White Mountains was known as Lake Israel and extended from the Randolph area to Lancaster. Cherry Pond is a remnant of this long-ago glacial lake.
Besides Cherry Pond, evidence of the glacier can also be seen in several large boulders found just off the Little Cherry Pond Trail. These boulders are known as “erratics” and were transported by the ice sheet to this spot from elsewhere in the White Mountain region. To access the boulders, look for a short, unmarked path on your right as you head out to Little Cherry Pond on the western loop of the Little Cherry Pond Trail (Note: On the Pondicherry Wildlife Refuge Map & Guide, this loop is called the Goshawk Loop). You can see the boulders, covered in ferns, from the main trail.
Another interesting geological feature found at Pondicherry is the “ice push rampart.” Over the last 11,000 years, when the water in Cherry Pond has frozen, gravel and other sediments, as well as small boulders, have been pushed by the ice up onto the shore of Cherry Pond, creating a low berm (or rampart). On portions of the Shore Path and the Rampart Path, you actually walk on top of this rampart and can easily see this unusual phenomenon.
If you would like to read more about the Laurentide Ice Sheet and how it shaped the landscape in the White Mountain region, a good book to consult is The Geology of New Hampshire's White Mountains, by J. Dykstra Eusden et al, published in 2013 by Durand Press. Also, on the WhiteMountainHistory.org website, there is a fascinating series of articles from the journal Windswept (published by the Mount Washington Observatory) which discuss the glacial lakes (including Lake Israel), as well as the PaleoIndians who first settled in this area after the ice sheet retreated. Included in this discussion is an explanation of sediment cores taken from Cherry Pond that shed light on the glaciation of this region.