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
Damtshaa diamond mine projected 31 year life of the mine. In 2003, the Damtshaa mine produced 292,000 carats (58.4 kg). Recovered ore grade averages about 0.06 carats (12 mg) per metric ton. The ore produced at Damtshaa is processed at a processing plant at its sister mine, the Orapa diamond mine, about distant. The Damtshaa mine is also managed from the Orapa mine, and is included in Orapa's and Letlhakane's safety and environmental programs, meaning that Damtshaa is also ISO 14001 certified. Damtshaa employs around 180 people. Damtshaa diamond mine The Damtshaa diamond mine is a diamond mine located in Botswana about west