In Azerbaijan, near the Caspian Sea, there’s a place called Gobustan where the ground burps. Not metaphorically—actually burps. Cold mud oozes up from cracks in the earth, plops into conical mounds, and occasionally explodes with enough force to hurl sediment hundreds of feet into the air. The locals call them mud volcanoes, which seems reasonable until you ask an actual volcanologist what they think about the name.
Turns out, they hate it.
The Thing About Real Volcanoes Is They’re Basically Geological Blowtorches
Real volcanoes—the Mount Etna kind, the Kilauea kind—are what happens when the Earth’s mantle gets so hot that rock melts into magma and punches through the crust like a fist through drywall. Temperatures hover around 700 to 1,200 degrees Celsius. That’s hot enough to vaporize water instantly, melt steel, and generally make everything in the vicinity regret existing. Mount Vesuvius buried Pompeii in 79 AD with superheated ash that moved at 450 miles per hour. Krakatoa’s 1883 eruption was heard 3,000 miles away—literally the loudest sound in recorded history.
Mud volcanoes? They top out at maybe 100 degrees Celsius on a really ambitious day. Most are closer to room temperature.
Here’s the thing: mud volcanoes are driven by pressurized gas—mostly methane—that gets trapped in sedimentary layers deep underground. When that gas finds a weakness in the overlying rock, it forces its way up, dragging water and clay along for the ride. The result looks volcanic—conical shape, central crater, periodic eruptions—but the chemistry is completley different. No magma. No molten rock. Just angry mud with ambition.
The largest mud volcano eruption in recent history happened in 2006 in Sidoarjo, Indonesia. A drilling company punctured a pressurized mud layer 9,000 feet down, and the earth started vomiting. At its peak, Lusi (as it’s called) was spewing 180,000 cubic meters of mud per day. It buried entire villages, displaced 60,000 people, and is still erupting today—nearly two decades later. The damage exceeded $4 billion.
Wait—maybe we should call that a disaster volcano instead.
When Geologists Argue About Vocabulary Like It’s a Blood Sport
The International Association of Volcanology and Chemistry of the Earth’s Interior—yes, that’s a real organization, and yes, they have opinions—officially does not recognize mud volcanoes as true volcanoes. Their argument hinges on the definition of “volcano” requiring molten rock. Mud volcanoes eject sediment and gas. Different process, different name. They prefer “mud diapir” or “sedimentary volcano,” which sounds like something you’d order at a mediocre restaurant.
But nomenclature aside, mud volcanoes do some genuinely volcanic things. They create landforms. They alter local geology. Azerbaijan has over 400 of them, including some that ignite when methane concentrations get high enough. The Dashgil mud volcano caught fire in 2001 and shot flames 50 feet into the air for hours. Witnesses said it looked like the earth was angry.
So are they real volcanoes? Depends on whether you prioritize process or appearance, chemistry or behavior. The mud itself is often ancient—some samples from Azerbaijani mud volcanoes contain microfossils from 20 million years ago, dredged up from depths where sunlight is a myth and pressure crushes everything into submission. It’s a window into geologic time, delivered via belch.
Trinidad has the Pitch Lake, which isn’t technically a mud volcano but behaves like one—a 100-acre asphalt seep that bubbles and occasionally spits up tar. New Zealand’s Rotorua geothermal area has boiling mud pools that aren’t volcanoes either, but good luck explaining that to tourists snapping photos. Semantics matter to scientists. To everyone else, if it looks like a volcano and acts like a volcano, it’s close enough.
The strangest part? Mud volcanoes might exist on Mars. The Mars Reconnaissance Orbiter identified features in the Acidalia Planitia region that look suspiciously like terrestrial mud volcanoes—conical mounds with summit craters, arranged in clusters. If Mars has subsurface water and gas deposits, the same physics that create Earth’s mud volcanoes could operate there. Which means the first “volcano” we study up close on another planet might not even be a real volcano.
That’s going to annoy someone at the International Association of Volcanology.
