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
Diamond mining in India Diamond mining in India Diamond mining in India extends back into antiquity. From ancient times, India was the source of nearly all the world's known diamonds, and until the discovery of diamonds in Brazil in 1726, India was the only place where diamonds were mined. India has not been a major diamond-producing country since the 1700s, but diamond mining continues. In 2013, India mined 37,515 carats of diamonds, from one industrial-scale mine and many artisanal mines; this was less than one-tenth of one percent of the world production of 132.9 million carats. Diamond mining as an industry appears to have