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
Baken diamond mine Baken diamond mine The Baken diamond mine is a diamond mine located along the lower Orange River in South Africa. The mine is owned and operated by Trans Hex. The central processing plant has been operational at Baken since 2001. In 2004 the Baken mine produced ; average stone size for the year was . Notable stones from production in 2004 included a , D colour flawless diamond that sold for over $1.8 million USD; and a pink diamond sold for over $1.0 million USD. Probable reserves are 21.2 million cubic meters of ore at an ore grade of per