North China craton
Encyclopedia
The North China Craton is one of the smaller continent
al craton
s of the Earth
. It covers a total area of around 1.7 million square kilometres (655,500 square miles) in the northeast of China
, most of Korea
and the southern part of Mongolia
, and has a shape quite akin to a funnel
, with a long east-west axis in the western part and two shorter perpendicular axes in the eastern half.
over time as a result of collisions with other continent
al land masses. The main blocks comprise the Eastern Block, the Western Block and the Central Orogenic Belt. The Central Orogenic Belt runs from western Liaoning
through Beijing
municipality to western Henan
and contains chiefly igneous rock
s of Paleoproterozoic
age. The Western Block extends west from this region through Shanxi
, Shaanxi
, Inner Mongolia
and northern Gansu
. This block is the oldest and most stable part of the Craton and contains some of the oldest and mineralogically most valuable rocks in Asia
, especially in Inner Mongolia where huge deposits of coal
and iron ore are found.
The Eastern Block is unusual for a craton in that it is affected severely by crustal thinning that began in the Mesozoic
and is known to have reduced the thickness of the crust from 200 kilometres to as little as 80 kilometres. In the Changbai Mountains
and Shandong
there has been extensive volcanism
in the Tertiary. The crustal thinning of the Eastern Block is believed to be due to high heat flow within the plates (especially the Pacific Plate
) surrounding the North China Craton.
Prior to the Triassic
, the North China Craton was an independent continent surrounded by oceans. For most of the Paleozoic
, it was located in the extreme north of the Earth
, often being the northernmost land in the world until it collided with Siberia
to comprise the last stage in the formation of Pangaea
during the Triassic.
, one of the most densely populated rural regions in the world. It is drained chiefly by the lower reaches of the Huang He and Hai He, both of which are among the siltiest rivers in the world and provide enormous amounts of essential plant nutrients when they flood during the summer. The climate of the North China Plain is humid but continental
, with most precipitation
occurring between June and September, though significant falls in winter do occur in the southern part of the region. Annual rainfall in the southern part of the North China Plain averages around 1,150 millimetres (45 inches), but declines to around 600 millimetres (24 inches) in the north. Temperatures vary widely, but summer is always hot with the average July maximum usually around 31 °C (88 °F) with high humidity. January temperatures range from about 3 °C (37 °F) in the extreme south to −10 °C (14 °F) north of Beijing.
In complete contrast, the Western Block is a dry, elevated plateau
averaging over 1,000 metres (3,300 ft) in elevation and having a dry and extremely continental climate. Annual rainfall is typically only around 300–400 millimetres (12–16 inches) and winter temperatures are often as low as −20 °C (−4 °F), whilst summers can be blistering. Because of the huge accumulations of loess
from Himalayan glaciation, the soils are very fertile when irrigated
, but water shortages remain a serious problem for farmers. Sheep are grazed in large numbers away from the rivers.
The Central Orogenic Belt is mainly rocky mountains up to 2,360 metres (7,740 ft) in elevation. Because of the extreme cold and erosion risk, most of this mountainous land is not cultivated and in places extensive forest
s still remain.
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
al craton
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
s of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. It covers a total area of around 1.7 million square kilometres (655,500 square miles) in the northeast of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, most of Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
and the southern part of Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
, and has a shape quite akin to a funnel
Funnel
A funnel is a pipe with a wide, often conical mouth and a narrow stem. It is used to channel liquid or fine-grained substances into containers with a small opening. Without a funnel, spillage would occur....
, with a long east-west axis in the western part and two shorter perpendicular axes in the eastern half.
Geological history
The North China Craton is composed of several major blocks that have been heavily tilted and foldedFold (geology)
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...
over time as a result of collisions with other continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
al land masses. The main blocks comprise the Eastern Block, the Western Block and the Central Orogenic Belt. The Central Orogenic Belt runs from western Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
through Beijing
Beijing
Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...
municipality to western Henan
Henan
Henan , is a province of the People's Republic of China, located in the central part of the country. Its one-character abbreviation is "豫" , named after Yuzhou , a Han Dynasty state that included parts of Henan...
and contains chiefly igneous rock
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
s of Paleoproterozoic
Paleoproterozoic
The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
age. The Western Block extends west from this region through Shanxi
Shanxi
' is a province in Northern China. Its one-character abbreviation is "晋" , after the state of Jin that existed here during the Spring and Autumn Period....
, Shaanxi
Shaanxi
' is a province in the central part of Mainland China, and it includes portions of the Loess Plateau on the middle reaches of the Yellow River in addition to the Qinling Mountains across the southern part of this province...
, Inner Mongolia
Inner Mongolia
Inner Mongolia is an autonomous region of the People's Republic of China, located in the northern region of the country. Inner Mongolia shares an international border with the countries of Mongolia and the Russian Federation...
and northern Gansu
Gansu
' is a province located in the northwest of the People's Republic of China.It lies between the Tibetan and Huangtu plateaus, and borders Mongolia, Inner Mongolia, and Ningxia to the north, Xinjiang and Qinghai to the west, Sichuan to the south, and Shaanxi to the east...
. This block is the oldest and most stable part of the Craton and contains some of the oldest and mineralogically most valuable rocks in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, especially in Inner Mongolia where huge deposits of coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
and iron ore are found.
The Eastern Block is unusual for a craton in that it is affected severely by crustal thinning that began in the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
and is known to have reduced the thickness of the crust from 200 kilometres to as little as 80 kilometres. In the Changbai Mountains
Changbai Mountains
The Changbai Mountain Range or Jangbaek Mountain Range are a mountain range on the border between China and North Korea...
and Shandong
Shandong
' is a Province located on the eastern coast of the People's Republic of China. Shandong has played a major role in Chinese history from the beginning of Chinese civilization along the lower reaches of the Yellow River and served as a pivotal cultural and religious site for Taoism, Chinese...
there has been extensive volcanism
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
in the Tertiary. The crustal thinning of the Eastern Block is believed to be due to high heat flow within the plates (especially the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
) surrounding the North China Craton.
Prior to the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
, the North China Craton was an independent continent surrounded by oceans. For most of the Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
, it was located in the extreme north of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, often being the northernmost land in the world until it collided with Siberia
Siberia (continent)
Siberia is the craton located in the heart of the region of Siberia. Siberia or "Angaraland" is today the Central Siberian Plateau...
to comprise the last stage in the formation of Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
during the Triassic.
Geography
The Eastern Block of the North China Craton consists mainly of the densely settled and very fertile North China PlainNorth China Plain
The North China Plain is based on the deposits of the Yellow River and is the largest alluvial plain of eastern Asia. The plain is bordered on the north by the Yanshan Mountains and on the west by the Taihang Mountains edge of the Shanxi plateau. To the south, it merges into the Yangtze Plain...
, one of the most densely populated rural regions in the world. It is drained chiefly by the lower reaches of the Huang He and Hai He, both of which are among the siltiest rivers in the world and provide enormous amounts of essential plant nutrients when they flood during the summer. The climate of the North China Plain is humid but continental
Continental climate
Continental climate is a climate characterized by important annual variation in temperature due to the lack of significant bodies of water nearby...
, with most precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
occurring between June and September, though significant falls in winter do occur in the southern part of the region. Annual rainfall in the southern part of the North China Plain averages around 1,150 millimetres (45 inches), but declines to around 600 millimetres (24 inches) in the north. Temperatures vary widely, but summer is always hot with the average July maximum usually around 31 °C (88 °F) with high humidity. January temperatures range from about 3 °C (37 °F) in the extreme south to −10 °C (14 °F) north of Beijing.
In complete contrast, the Western Block is a dry, elevated plateau
Plateau
In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
averaging over 1,000 metres (3,300 ft) in elevation and having a dry and extremely continental climate. Annual rainfall is typically only around 300–400 millimetres (12–16 inches) and winter temperatures are often as low as −20 °C (−4 °F), whilst summers can be blistering. Because of the huge accumulations of loess
Loess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...
from Himalayan glaciation, the soils are very fertile when irrigated
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
, but water shortages remain a serious problem for farmers. Sheep are grazed in large numbers away from the rivers.
The Central Orogenic Belt is mainly rocky mountains up to 2,360 metres (7,740 ft) in elevation. Because of the extreme cold and erosion risk, most of this mountainous land is not cultivated and in places extensive forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
s still remain.