This hole in the ice is located on Lake Siljan in Sweden – and is a mystery. As residents report, it is created there every year in approximately the same place, as well as several other holes. Researchers from the Technical University of Chalmers in Gothenburg, Sweden, have now taken on this puzzle, but only partially solved it.
As the team found out, the unusual holes arise from large amounts of methane that emerge from the seaside area. “At certain locations, we measured emission rates that are up to 300 times higher than the typical values in lakes,” reports team member Johan Mellqvist. An estimated 3.5 tons of methane escapes from Lake Siljan every year. This corresponds to 85 tons of CO2 equivalents.
But where does all the methane come from? One possibility is that it is so -called deep gas from the underground – caused by a meteorite impact in the region that has been 370 million years ago. This could have carried organic material deep into the earth where it has decayed and still emits methane. Another possibility is that the emissions come from methane bubbles – enclosed gas in sediments under the sea grade, which gradually escapes, as the researchers report.
“If it is deep gas, this could only occur in the impact crater. However, if it comes from flatter sediment pockets, this type of emission could occur in many more places,” explains Mellqvist. Then, in turn, the global greenhouse potential of this phenomenon would be considerable and would have to be contained as quickly as possible.