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
Luarica diamond mine of ore at an ore grade of per 100 cubic meters (43.2 mg/m³). There is a waste rock overburden of about 9.5 million cubic meters. Mining operations were suspended in May 2009 due to a decline in diamond demand caused by the late-2000s financial crisis. Trans Hex announced in August 2011 that it planned to withdraw from its two Angola joint-ventures with Endiama—Luarica and Fucauma—after failing to reach an agreement with the government of Angola (which owns the other major partner, Endiama). Endiama stated that it planned to restart operations alone. Luarica diamond mine The Luarica diamond mine is a