Gas explosion craters in permafrost

This is an interesting article from the BBC web site:

https://www.bbc.com/future/article/20201130-climate-change-the-mystery-of-siberias-explosive-craters

It describes a series of craters formed in Siberia, where a rather unique combination of factors in the permafrost layers causes a buildup of methane gas trapped beneath the surface frozen layer, and then an explosion which leaves a spectacular steep-sided crater behind.  Some of the explosions are accompanied by flames and smoke.  There are no observations of a natural explosive methane gas event actually happening, but as the permafrost continues to melt, there will be more and more of them.......