Methane is colorless and odorless and it is right above us in the atmosphere.
In addition to other sources, methane has traveled from the Arctic and has blanketed most of the Northern Hemisphere.
The well known sources are methane hydrates from the Arctic Ocean floor and methane coming from thawing permafrost.
There is also another less well known source. During the geologic history of the Arctic area, tectonic plates have spread, crashed into each other and subducted under one another. Geologists call the Arctic a tectonic plate junkyard. There are numerous fractures in the earth’s crust there.
A quote from earth scientist Malcolm Light: “Mantle methane formed from the reduction of oceanic carbonates by water in the presence of iron (II) oxides buried to depths of 100 km to 300 km in the Asthenosphere and at temperatures above 1200°C.” This is a non-organic source of methane formed near the earth’s mantel. Katey Walter from the University of Alaska calls it geologic methane.
Vast reservoirs of methane have been created by chemical reactions and stored near the mantle under a lot of pressure for millennia.
The methane has had a route to the surface through the fractures in the earth’s crust, but the fractures have been sealed over by ice. Now for the first time in human history, the ice sealing the fractures is thawing. Methane is rising through the fractures and into the atmosphere. This methane has migrated to the United States and is over us.