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Geologic Map
Shaded Relief
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Generalized Geologic Map of the Conterminous United States
North America Shaded Relief


  The North American Tapestry of Time and Terrain

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Legend and Rock Ages
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Political Boundaries


Mesozoic Hog-back Ridge


Close-up of
 hogback ridge
The hooked north-south ridge (green on the map) just north of New York's Long Island is a cuesta or hog-back ridge, one of several tilted and eroded lava flows in the Connecticut Valley. It is contained within coarse Triassic-Jurassic sediments that were deposited rapidly during the rift-faulting of North America, about 180-200 million years ago, as the supercontinent Pangaea was pulled apart and Europe and Africa separated from North America. When you are visiting Normandy in western France, you can find matching rocks.