Permafrost by permafrost. Of this area slightly more than half is underlain by continuous permafrost, around 20 percent by discontinuous permafrost, and a little less than 30 percent by sporadic permafrost. Most of this area is found in Siberia, northern Canada, Alaska and Greenland. Beneath the active layer annual temperature swings of permafrost become smaller with depth. The deepest depth of permafrost occurs where geothermal heat maintains a temperature above freezing. Above that bottom limit there may be permafrost, whose temperature doesn't change annually—"isothermal permafrost". Permafrost typically forms in any climate where the mean annual air temperature is less than the
Charles E. Fipke a heavy mineral and diamond exploration research laboratory. In 1983, he founded Dia Met Minerals, which became listed on the Vancouver Stock Exchange in 1984. Dia Met was sold to BHP Billiton in 2001. In 1988, Fipke and partner Stu Blusson began a systematic search for diamonds in the Northwest Territories, leading to the discovery of the first diamond pipe in North America in November 1991 near Lac de Gras. The Ekati Diamond Mine is now located there. Fipke maintained a 10% interest in Ekati until 2014, when he sold his share to Dominion Diamond Corp. for . "I'm not