All this history took place in the Paleozoic Era from 500 to 250 million years ago, which accounts for the traditional dense, saturated colors used on the map. The green, blue, and purplish areas are the metamorphic rocks, and the warm colors are the granites. The general fabric of the state runs parallel to the rest of the mountain ranges of the eastern United States. The yellow blobs are later intrusions related to the opening of the Atlantic, mostly during the Triassic, around 200 million years ago.
From then until nearly the present, the history of the state was one of erosion. The Pleistocene ice ages brought deep glaciers to the whole state. A surface geologic map, showing the glacial deposits and landforms, would look very different from this one.
I have two apologies. First, I left off the tiny Isles of Shoals, which sit offshore past the lower right corner of the state. They look like dirt specks, and they're too small to show any color. Second, I apologize to my old professor Wally Bothner, the map's first author, for the mistakes I've surely made interpreting this map.
See this map in a 1200x1600 pixel version (340 KB) that includes the key to all the colors. Or you could get your own copy from the state Department of Environmental Services as a free PDF.
More about New Hampshire Geology
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New Hampshire Skiing
New Hampshire Fishing
New Hampshire Maple Sugaring
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New Hampshire Historic Sites
