A bubbling mud volcano was captured on camera by a Canadian scientist in southern Taiwan.
The Yangpu pond remains something of a scientific mystery and can burn for five minutes after being set alight.
The phenomenon results from bacteria in the mud using organic material and water to generate methane, which is subsequently released in the pond.
Professor Shahin Dashtgard from British Columbia's Simon Fraser University said: "There are abundant marine mudstones that are not well lithified [when sediment becomes rock over many years] in the Kaohsiung area.
"The mudstones are young, have lots of organic material and are more mud than rock.
"The intense tectonic stress on Taiwan and the abundant rainfall mix with the mud to turn it into liquid, which forms the mud volcanoes."
According to Professor Dashtgard, locals regularly light the pond on fire seemingly to attract visitors.