Ponds forming from thawing permafrost, satellite image. In Earth's cold regions, much of the sub-surface ground is frozen. Permafrost is frozen soil, rock or sediment, sometimes hundreds of metres thick. Permafrost holds carbon-based remains of vegetation and animals that froze before they could decompose. When permafrost warms and thaws, it releases methane and carbon dioxide, adding these greenhouse gases to the atmosphere and making global warming even worse. These ponds have formed in the Yamal Peninsula in northwest Siberia, Russia. Image obtained on 27 August 2018, by one of the Copernicus Sentinel-2 satellites.