Northeast" in official documents in the newly founded Republic of China, in addition to the "Three Northeast Provinces". During the Ming dynasty the area where the Jurchens lived was referred to as Nurgan. Nurgan was the area of modern Jilin in Manchuria. Geography and climate Manchuria consists mainly of the northern side of the funnel-shaped North China Craton, a large area of tilled and overlaid Precambrian rocks spanning . The North China Craton was an independent continent before the Triassic period and is known to have been the northernmost piece of land in the world during the Carboniferous. The Khingan Mountains in the west are a Jurassic mountain range formed by the collision of the North China Craton with the Siberian Craton, which marked the final stage of the formation of the supercontinent Pangaea. No part of Manchuria was glaciated during the Quaternary, but the surface geology of most of the lower-lying and more fertile parts of Manchuria consists of very deep layers of loess, which have been formed by the wind-borne movement of dust and till particles formed in glaciated parts of the Himalayas, Kunlun Shan and Tien Shan, as well as the Gobi and Taklamakan Deserts. Soils are mostly fertile mollisols and fluvents except in the more mountainous parts where they have poorly developed orthents, as well as in the extreme north where permafrost occurs and orthels dominate. The climate of Manchuria has extreme seasonal contrasts, ranging from humid, almost tropical heat in summer to windy, dry, Arctic cold in winter. This pattern occurs because the position of Manchuria on the boundary between the great Eurasian continental landmass and the huge Pacific Ocean causes complete monsoonal wind reversal. In summer, when the land heats faster than the ocean, low-pressure forms over Asia and warm, moist south to southeasterly winds bring heavy, thundery rain, yielding annual rainfall ranging from , or less in the west, to over in the Changbai Mountains. Temperatures in summer are very warm to hot, with July average maxima ranging from in the south to in the extreme north. In winter, however, the vast Siberian High causes very cold, north-to-northwesterly winds that bring temperatures as low as in the extreme south and in the north where the zone of discontinuous permafrost reaches northern Heilongjiang. However, because the winds from Siberia are exceedingly dry, snow falls only on a few days every winter, and it is