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
Jwaneng diamond mine 2,100 people. The mine also owns and operates a local hospital and Jwaneng Airport. The mine maintains an ISO 14001 certificate for environmental compliance, being the first mine in Botswana to achieve this certification in 2000. Jwaneng is known for its excellent safety record, winning multiple national and international safety awards. The Enhanced Thematic Mapper Plus (ETM+) instrument on NASA’s Landsat 7 satellite acquired this image of the Jwaneng Diamond Mine on May 17, 2001. The arid, flat landscape that fills most of this image appears in varying shades of brown, crisscrossed by pale beige roads. The Jwaneng Diamond Mine