I have lived in New England at this point for the greater part of my life, and yet, I had somehow never been to Cape Cod until this past weekend. Nothing like driving down towards an exposed expanse of sand in the midst of a nor’easter to make you aware of the odd geography of that stretch of the coast. While my attention was focused on the shoreline, which was being whipped by rain and wind, it was the interior pools of water that helped me to understand how this landscape came to be.

The pools I’m describing here are known as “kettle ponds” and were formed by giant blocks of ice left behind by retreating glaciers. Given the weekend’s balmy temperatures, this was a little hard to imagine. Essentially, the chunks of ice that were left behind became buried in sediment that helped to insulate them from melting more quickly. Then, as they melted, they softened the earth around them, which then collapsed into holes, which then filled with water. They are just a piece of the bigger story of Cape Cod’s formation as the Laurentide ice sheet retreated and left behind vast areas of sediment that were then shaped by coastal currents into the characteristic hook shape. The carving of the coastline is dynamic such that storms and changing sea levels continue to change the position of sand bars, heights of dunes and shape of the inlets.

Maine, too, was shaped by glaciers. But the bedrock underneath our state makes its story different such that the shape of the coast is more a result of scraping and scouring that make our coast so rugged and convoluted rather than sandy and smooth. Inland, however, we also have kettle ponds. One of Maine’s most well-defined sets of kettle ponds stretches between the northern part of Augusta and Belgrade.

There is another set of similar depressions, though, that is much more extensive and is found along the coast. These are the little pockets of water found throughout salt marshes known as “salt pannes.” Glaciers didn’t form these, but they were similarly formed by chunks of ice — a process that happens every winter, repeatedly reshaping the marsh. The vegetation around these ice chunks dies, leaving behind a depression that then fills with water. These are unique ecosystems that are important for the health of the salt marsh as well as the surrounding tidal areas. Salt pannes are prime habitats for tiny fish and invertebrates that are protected there from larger predators. Birds, however, find ample food here and are often seen dipping or wading into these shallow pools.

This fall, as you look across the sandy-colored marsh grasses, look for the pockets of water among them and imagine how they might shift and change this winter in less dramatic ways than the glaciers that shaped the kettle pools but in ways that are ecologically significant to our coast.

Susan Olcott is the director of strategic partnerships at Maine Coast Fishermen’s Association.