New Hampshire's Ancient Volcanoes

Hi, this is Scott Fitzpatrick from New Hampshire Audubon, bringing you Something Wild.

This week, I thought it might be fun to go WAY back in time, to when the New Hampshire we know and love was still being formed. Let’s take a trip to the Jurassic Period, or around 200 million years ago…

[sci-fi sound effect]

OK… are you with me? Back then, New Hampshire was still tropical, and dinosaurs reigned triumphant. But it’s the geology I want to explore. The North American Plate was slowly splitting apart into North America, Europe, and Africa and the Atlantic Ocean was just being formed. Magma, or molten rock, would sometimes emerge on the surface as volcanoes. Volcanoes in New Hampshire? That’s right—and you can still see the evidence of them if you know where to look.

The Ossipee Mountains are considered by many geologists to be the best example in the world of a ring dike formation. These structures form when an underground bubble of magma collapses, leaving a circular crack on the surface. Magma then erupts through these cracks creating ring-shaped mountain ranges. The Ossipee Mountains are a nearly perfect circular range, ten miles in diameter, located at the center of an ancient volcanic crater. This area contains nearly a dozen peaks above 2,000 feet.

The Pawtuckaway Mountains are another classic, but smaller, example of an eroded volcanic crater. And the Belknap mountains, together with the Rattlesnake and Diamond Islands, forms a large, but less noticeable crater on the south side of Lake Winnipesaukee.

You can clearly see these formations on topographic and geological maps of the state. All of these former volcanoes offer great hiking trails, some with spectacular lake views. So get out there and explore the ancient volcanoes in your own backyard.

For Something Wild, I’m Scott Fitzpatrick.

Something Wild is a joint production of New Hampshire Audubon, New Hampshire Public Radio, and the Society for the Protection of New Hampshire Forests.