Manchuria - Geography and Climate

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. The North China Craton was an independent continent prior to 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.

Although no part of Manchuria was glaciated during the Quaternary, the surface geology of most of the lower-lying and more fertile parts of the region consists of very deep layers of loess, which have been formed by the wind-born 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 are poorly developed Orthents, as well as the extreme north where permafrost occurs and Orthels dominate.

The climate of Manchuria has extreme seasonal contrasts, ranging from humid, almost tropical heat in the summer to windy, dry, Arctic cold in the winter. This occurs because the position of Manchuria is on the boundary between the great Eurasian continental landmass and the huge Pacific Ocean causes complete monsoonal wind reversal.

In the summer, when the land heats up 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 400 mm (16 in.), or less in the west, to over 1150 mm (45 in.) in the Changbai Mountains. Temperatures in the summer are very warm to hot, with July average maxima ranging from 31°C (88°F) in the south to 24°C (75°F) in the extreme north. Except in the far north near the Amur River, high humidity causes major discomfort at this time of year.

In the winter, however, the vast Siberian High causes very cold, north to northwesterly winds that bring temperatures as low as −5°C (23°F) in the extreme south and −30°C (−22°F) 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 never heavy. This explains why, whereas corresponding latitudes of North America were fully glaciated during glacial periods of the Quaternary, Manchuria, though even colder, always remained too dry to form glaciers – a state of affairs enhanced by stronger westerly winds from the surface of the ice sheet in Europe.