This page tells about permafrost. It includes a video.
What is Permafrost?Permafrost is any combination of soil, rock, ice, and organic material found on or in the ground that has maintained a temperature colder than freezing for two or more years. The sole determinant of whether a stretch of ground is permafrost or not is its temperature. Permafrost commonly forms in climates with a mean annual air temperature of zero degrees Celsius (or thirty-two degrees Fahrenheit) or colder; therefore, it is very commonly found in the Arctic, sub-Arctic, and Antarctica.
About twenty percent of the world's land surface is comprised of permafrost, and some of it has been frozen for tens or hundreds of thousands of years. This is because most modern day permafrost formed during glacial periods thousands of years ago and maintained its temperature during warmer interglacial periods as well. Some permafrost is found under a layer of soil and can be anywhere from three to thousands of feet thick.
Reservoir of Carbon
Permafrost's long-lasting ability combined with its freezing temperatures provides an ideal location for storage of samples of history. Carbon-based remains of plants, animals, and organic material that froze before decomposing are stored in permafrost over time. Due to this accumulation of carbon in the form of organic material, the world's permafrost currently harbors approximately 1.5 billion tons of carbon; this amount is almost twice the amount of carbon found in our atmosphere. While these staggering amounts of carbon cannot do much harm while frozen under the ground, they do have the ability to contribute to climate change and global warming if the permafrost thaws and melts - which is occurring in the Arctic and other parts of the world. It is currently estimated that by the year 2040, 110 to 231 billion tons of carbon dioxide and methane-related gases will be emitted due to permafrost thawing; these steep levels of release could severely exacerbate the effects of climate change and global warming. The high consequences of permafrost thawing make it important now more than ever to study and preserve these key expanses of ground.