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
Catoca diamond mine at the average rate of US$62.23, a volume that represented about 78 percent of the amount sold by the diamond companies around the country. The note states that as a result of the processing of the ore, the company obtained a total of 7.5 million carat that permitted to establish the operational costs. In 2012 the mine produced 6.5 million carats out of 10 million metric tons of ore production. The Catoca diamond deposit occurs in a kimberlite pipe. Catoca diamond mine The Catoca diamond mine is the fourth largest diamond mine in the world, and is located in Angola.