Are there any remnants of old, long dead volcanoes in New Hampshire?

According to New Hampshire Geology,

“The Jurassic Period [jer-AA-sick] was a very geologically active and exciting period in New Hampshire. The rifting of the North American Plate from the African and European Plates was starting to open up the brand new Atlantic Ocean. Molten rock, or magma, would sometimes rise up through the crust and erupt as a volcano and other times it just got close to the surface. Keep in mind that “close to the surface” still meant 3 to 5 miles below the surface, because on average, the Earth’s plates are about 20 miles thick. New Hampshire was still tropical, and dinosaurs reigned supreme.”�Some of the ‘yellow blobs’ discussed above represent some classic, world famous (among geologists anyhow) nearly circular volcanic mountains known as ring dikes. A dike is a crack in the bedrock that is filled in with intruding material, in this case, magma. A ring dike is a circular crack formed by the collapse of a magma chamber’s ceiling underground. The magma blobs tended to be rounded in shape, not unlike the “lava” blobs in a lava lamp. Magma erupted through these circular structures throughout the state yielding several textbook examples of circular ring dike mountains. The best known and largest example in New Hampshire are the Ossipee Mountains in Moultonborough, Sandwich, Tamworth, Ossipee and Tuftonborough seen in the box at right. Another excellent example, albeit much smaller, is Mt. Pawtuckaway in Pawtuckaway State Park.”

For more excellent information, check out their website at: New Hampshire Geology


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