Mud volcanoes, unlike many others, do not extrude lava. Instead, they release glutinous bubbling brown slurry of mineral-rich water and sediment. They range in size from several kilometres across, to less than a metre – the little ones are known as mud pots, reflecting their diminutive nature. The world’s largest, though, is Lusi: a mud volcano in East Java that released an astonishing 180,000 cubic metres of fluid each day during the peak of its 2006 eruption. It’s likely to continue erupting for another 26 years!

Much of the gas that bubbles up through these muddy pools is methane, though the exact mix of gasses varies from site to site and is tied to other geological activity in the region, with those close to igneous volcanoes often releasing less methane than those associated with clathrate deposits. Small bubbles of gas can coalesce to form a much larger one, which, on reaching the surface, bursts and sends flecks of clayey fluid asunder, just as they do here:

By Sara Mynott, EGU Communications Officer

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