Most of the state's lakes were formed by the action of the great glaciers that
covered the state four times to enormous depths of 8,000 feet or more. Grinding relentlessly over the earth, they dug basins that filled with water to become lakes. Sometimes glacial till formed natural dams, which backed up water for miles.

Glaciers formed many of the natural features of present day New Hampshire. In addition to the lakes, huge circular valleys, known as glacial cirques, were scooped out. These form some of the most attractive scenery in the state. Southern New Hampshire has many hills shaped like whales' backs. These hills, sometimes clay and sometimes rock or other material, are called drumlins.

The glaciers were most "generous" to the state in the gift of boulders. They were trundled overland from their original sites with infinite slowness and "graciously" deposited in New Hampshire when the ice melted. These are found in incredible numbers and sizes. Some areas are entirely covered with great glacial boulders in weird and jumbled masses.

It is hard to believe that the boulders, even on the lofty top of Mt. Washington, were deposited there by glaciers. The Madison boulder is said to be the largest "erratic" boulder in the United States. It weighs almost 8,000 tons (7,257 metric tons) and is over 80 feet (24 meters) long.

New Hampshire's famous flumes are also relics of the Ice Age, as are the Polar Caves near West Plymouth. 

The weight of the glaciers was so tremendous that the level of the land was
pressed down much lower than it now is. When the ice melted, the land began to rise slowly, like a sponge that expands when it is no longer being squeezed. The melting ice also raised the level of the seas, and parts of New Hampshire that had once been land were submerged. The famous Drowned Forest near Jenness Beach was probably growing on the New Hampshire shore until the sea rose to overwhelm it.

Many major features of New Hampshire were formed by forces much older than the glaciers. Fantastic slow upward and downward movements of the land raised mountain chains or brought in shallow seas. Much of the mountain region owes its present form to the centuries-old processes of erosion. The enormous quantities of granite that are such a marked feature of the state were forced to the surface by the forces of heat and pressure deep in the earth.

New Hampshire divides naturally into six geographical districts: the North
Country and the White Mountain Region, the Monadnock Region, the Lakes District, the Connecticut River Valley, the Merrimack Valley, and the Eastern Seacoast.