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
Ekati Diamond Mine 62-million-year-old kimberlite pipes (Creaser et al., 2004) of the Lac de Gras kimberlite field, most of which lie underneath shallow lakes. Between 1998 and 2009, the mine has produced 40 million carats () of diamonds out of six open pits. As the high grade ore close to surface was depleted, development was completed to access the ore utilizing underground methods. Currently, there is one underground operation (Koala) with open-cut mining occurring in Fox Pit. The mine's current annual production is estimated to be approximately 7.5 million carats () of diamonds. Ekati supplies rough diamonds to the global market through its