An incredible tornado of gas and fire, swirling 3,280ft (1km) into the air, has been captured on Wednesday last week above Iceland's rumbling Bardarbunga volcano, which has been exhibiting seismic activities and eruptions since last month with some of its lava fountain reaching as high as 700 feet in the air.

The footage was taken last week by an aircraft-fitted infrared camera designed to monitor and allow pilots to see potentially dangerous ash clouds.

Scientists are still unsure what caused the tornado-like phenomenon, but have suggested it may be due to the difference between hot and colder air rising above Bardarbunga (located under Vatnajökull, Iceland's most extensive glacier) has caused something similar to a 'dust devil'.

Dust devils are small, rotating columns of air, which can be seen because of the dust and debris they pick up from the ground. They form because hot air close to the ground rises, punching through the layer of cooler, denser air above.

The rising plumes of hot air and falling plumes of cool air begin circulating vertically in something known as 'convection cells'. If a horizontal gust of wind blows, it turns the circulating air cells, so they begin spinning horizontally, forming vertical columns and starting a dust devil.

Fred Prata, Chief Technology Officer of the Nicarnica Aviation in Kjeller, Norway, and the inventor of the specially-designed infrared camera mentions that the volcano tornado could likely be a spinning sulfur dioxide gas that is similar to a fire tornado.

He said, "The generation mechanism is probably the same as that for dust devils, but in this case the tornado funnel is most likely filled with sulphur dioxide, gas and volcanic ash".

The Icelandic Meteorological Office has already warned of the possible dangers associated with the volcano tornadoes. Last week, officials arrested tourists who ventured too close to the hazard zone. Scientists and journalists were also asked to leave the lava field the same day the volcano tornadoes appeared due to the hazardous conditions.