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 Damtshaa diamond mine The Damtshaa diamond mine is a diamond mine located in Botswana about west of the city of Francistown. Damtshaa, meaning "water for a tortoise", is owned by Debswana, a partnership between the De Beers company and the government of Botswana. It is the newest of four mines operated by the company, officially opening on October 25, 2003. Damtshaa is of open pit construction, located on top of four distinct kimberlite pipes of varying ore grade. The mine is forecast to produce about 5 million carats (1,000 kg) of diamond from 39 million tons of ore over the