In the western part of this Sussex County township, in the area called Beemerville, the already hilly landscape abruptly ascends 200 feet via a private, residential road.
At the peak of this formation, standing over 1,000 feet above sea level, lies a flat rock spanning a diameter of more than a quarter-mile.
Remarkably, this is the sole remaining evidence of what was once an active volcano, whose cone was flattened during the Ice Age by a one-mile-thick sheet of ice.
Referred to as Mt. Rutan or Rutan Hill, named after a family that settled in the region, or Volcanic Hill, today there is at least one house built into the hillside.
Rutan Hill is not your typical volcano. It has no crater, and it did not spew lava like the ones in Hawaii or Iceland. Instead, it is a geological feature known as a diatreme: a vertical, pipe-like structure through which gas-rich magma that originated in the Earth’s mantle rose explosively. The force of the rising magma fractured bedrock formations at depths that the magma passed through, creating a rock that contains fragments welded together by the force, called breccia.
Rutan Hill last erupted hundreds of millions of years ago, during the Devonian Period, when New Jersey was part of a continent called Laurentia. The exact date of the eruption is uncertain, but some estimates range from 360 million to 440 million years ago.
Rutan Hill is a rare and fascinating example of New Jersey’s volcanic history, which is not widely known or studied. Wayne McCabe, Sussex County historian, said he gets a question about the history of the volcano about once every 10 years. “It’s interesting that we still have one example of that here in our county, and to the best of my knowledge we don’t have anywhere else in the state,” McCabe said.
Rutan Hill is also a part of the local culture and heritage, as it has been used by farmers and settlers for various purposes over the years.
Space also said that geologists still come to the zoo from time to time, asking for more information about the volcano. He said that even though the volcanic remains are surrounded by private land, if you take a pilgrimage to the northern tip of New Jersey and keep a sharp eye out, you can get a good view. “It’s kind of neat when you drive by, you can see it pretty explicitly — if you know what you’re looking at, is the hardest thing,” he said.
Rutan Hill is not the only volcano-type hill in the area. There is also a smaller one nearby, which Space said is not as well preserved. Both hills are part of the Appalachian Mountains, which were formed by the collision of tectonic plates that also caused volcanic activity.
“A lot of the stone walls, you can still see the volcanic rock in, and it’s because the farmers didn’t really care what it was when they were making a wall, clearing the land,” he said.
For McCabe, having a volcano — even a dormant one — in his region is a badge of honor, and indicative of the wide range of natural phenomena up and down New Jersey.
Relevant articles:
– Volcano in New Jersey? It’s ancient (and dormant), but it’s here
– A volcano in N.J.? Peeking into the depths of Beemerville’s prehistoric …
– Wantage Township boasts of its volcanoes – njherald.com