Paleontology and geology
During much of the Quaternary, thick sheets of ice covered New Hampshire. The weight of that ice depressed the surface of the land about 40 feet. As the glaciers melted, the land was able to rebound in elevation, and present sea level was reached approximately 3,000 to 5,000 years ago. The fossil evidence of plants and pollen from Pleistocene sediments in New Hampshire and neighboring states indicate that species of herbs and sedges, spruce, balsam poplar, willow, and dwarf birch trees grew in the area when the ice sheets periodically retreated. Similar species are now found in the arctic.