You’re driving down Route 23 in Sussex County, maybe headed toward High Point State Park, and you see it. A massive, jagged peak looming over the landscape. It looks suspiciously like a mountain that could blow its top at any moment. It makes you wonder: is there a volcano in New Jersey?
Short answer? No. Not anymore.
You aren't going to see lava flowing down the boardwalk in Asbury Park or ash clouds covering the Meadowlands anytime soon. But honestly, the real story is way cooler than a simple "no." New Jersey actually sits on top of some of the most violent geological history in North America. We’re talking about massive tectonic rifts, ancient magma chambers, and volcanic eruptions that make Mount St. Helens look like a sparkler.
The Beemerville Mystery
If you want to get technical about it, the closest thing New Jersey has to a "real" volcano is a spot called Beemerville in Wantage Township.
Specifically, look at Colesville. There is a 1,000-foot-high hill there known as Rutan Hill (sometimes called Volcanic Hill by the locals). If you stood there 440 million years ago during the Ordovician Period, you wouldn't be looking at rolling hills and dairies. You’d be standing on a literal volcanic neck.
What's a neck? Basically, it’s the "throat" of a volcano.
Magma pushed up through the Earth's crust, hardened in the pipe, and stayed there. Over hundreds of millions of years, the softer rock around it eroded away, leaving this plug of hard, exotic volcanic rock exposed. Geologists call the rock found here nepheline syenite. It’s rare. Like, really rare. In fact, Beemerville is one of the few places on the entire planet where you can find this specific mineral composition.
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It’s gray, grainy, and weirdly beautiful.
The Watchung Mountains: Lava on a Massive Scale
Most people living in North Jersey think the Watchung Mountains are just annoying hills that make their commute harder.
They’re actually solidified lava flows.
Roughly 200 million years ago, the supercontinent Pangea started to rip apart. Imagine the Earth literally cracking open. As the Atlantic Ocean began to form, massive fissures opened up in what is now the Newark Basin. Huge amounts of basaltic lava poured out. This wasn't a "boom" type of explosion like Vesuvius; it was more like the "flood basalts" you see in Hawaii or Iceland today.
These flows were deep. Really deep.
There were actually three separate volcanic events that formed the First, Second, and Third Watchung Mountains. We are talking about layers of igneous rock hundreds of feet thick. If you go to the Garret Mountain Reservation in Paterson or look at the cliffs along the Passaic River, you are looking at the cooling remains of a prehistoric hellscape.
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Why the Palisades Aren't Technically Volcanoes
People always get the Palisades confused with volcanoes.
It’s an easy mistake to make. The Palisades—those giant cliffs along the Hudson River—are made of diabase, which is an igneous rock. But here is the nuance: the Palisades are an intrusion, not an extrusion.
Basically, the magma never actually made it to the surface to erupt.
Instead, it got stuck between layers of sedimentary rock underground. It cooled slowly, forming those massive vertical columns that look like giant organ pipes. So, while it’s "volcanic" in origin, it never actually functioned as a volcano. It was more like a giant underground blister of molten rock that eventually saw the light of day once the glaciers and rain scrubbed the top layers off.
Is the Danger Real?
I get asked this a lot: "Could one of these things wake up?"
Probably not.
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The tectonic plates have moved on. New Jersey is now smack in the middle of a "passive margin." We aren't on a fault line where subduction is happening, which is the recipe for volcanic activity. The hotspots that fueled the Beemerville eruption and the Watchung flows are long gone. You’re more likely to be hit by a rogue bagel than an eruption in the Garden State.
That said, the ground still moves. We had that 4.8 magnitude earthquake in April 2024 centered near Whitehouse Station. That happened on the Ramapo Fault, which is a relic of the same tectonic stretching that caused the ancient volcanoes. So, while the volcanoes are dead, the scars they left on the crust are still "creaky."
Where to See the Evidence Yourself
If you're a rock nerd or just want a cool weekend hike, you can actually visit these sites.
- High Point State Park Area: Around the Beemerville area, look for the dark, strange-looking rocks that don't match the limestone around them. That's your volcanic pipe.
- The Great Falls in Paterson: The water is falling over the edge of a massive basalt flow. You can literally touch the edge of a 200-million-year-old lava stream.
- Tripod Rock at Pyramid Mountain: While the rock itself was moved by glaciers, the entire mountain is a testament to the crazy geological upheaval of the region.
The fact is, the "volcano" question is a gateway to understanding why Jersey looks the way it does. The red soil in the central part of the state? That’s iron-rich sediment from the volcanic era. The ridges that define the skylines? All lava.
New Jersey isn't just malls and turnpikes. It's a graveyard of ancient fire.
Actionable Next Steps for Exploration
If you want to dive deeper into the volcanic history of the state, don't just take my word for it.
- Visit the Rutgers Geology Museum: It’s free (though check their hours) and they have incredible samples of the Beemerville nepheline syenite. You can see the minerals up close without having to trespass on private property in Sussex County.
- Hike the Watchung Reservation: Specifically, look for "The Deserted Village" area. The topography there is dictated entirely by how the lava cooled and eroded.
- Check out the New Jersey Geological and Water Survey website: They have interactive maps that show exactly where the volcanic rock units are located. You can plug in your own address to see if you’re living on top of an ancient lava flow.
Knowing the ground beneath your feet changes how you see the state. Next time you're stuck in traffic on I-280, look at the rock cuts on the side of the road. That dark, crumbly rock isn't just dirt—it's the cooling remains of a world that existed before the first dinosaur ever took a breath.