WANTAGE — On the western side of this Sussex County township, in the section known as Beemerville, the already mountainous terrain suddenly rises 200 feet up a private, residential road.

At the top of that formation, more than 1,000 feet above sea level, is flat rock more than a quarter-mile in diameter.

Believe it or not, it is the only known remnant of what was once an active volcano, its cone flattened during the Ice Age by a mile-deep slab of ice.

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It's known as Mt. Rutan or Rutan Hill, after a family that settled in the area, or Volcanic Hill. Today there is at least one house actually settled into the hillside.

And while everyone's definition of "ancient" differs depending on context, the description of Rutan Hill as an ancient volcano should be somewhat reassuring: It last erupted 360 million years ago, to the best guess of Wayne McCabe, Sussex County historian.

Assemblyman Parker Space, whose family also guards much of the region's history as the owner of Space Farms Zoo & Museum, said it could have been even longer ago, perhaps 440 million years.

He said geologists still come to the zoo from time to time, asking for more information.

Similarly, McCabe said he gets a question about the history of the volcano about once every 10 years.

Space said 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.

Space also mentioned a smaller volcano-type hill in the general vicinity, and said farmers used to raid both sites for cinders as the town was being built up.

"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.

"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.

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