A type of Pleistocene-age (formed 1.8 million to 10,000 years before present) permafrost that contains a significant amount of organic material with ice content of 50 to 90 percent by volume. Thawing yedoma is a significant source of atmospheric methane

https://nsidc.org/cryosphere/glossary/Y

https://www.colorado.edu/today/2015/10/26/study-shows-thawing-permafrost-quickly-turns-co2-climate-concern