The geology of China (or the geological structure of the People's Republic of China) consists of three Precambrian cratons surrounded by a number of orogenic belts. The modern tectonic environment is dominated by the continued collision of India with the rest of Asia starting 40–50 million years ago. This has formed the Himalaya and continues to deform most of China. China has vast mineral reserves, a significant earthquake risk in its western regions and rare isolated active volcanoes throughout the country. Many geological concepts were discovered very early in China's history. However, it was not until the adoption of European natural science in the late 19th century that geology became a science in China. Landscape evolution The geomorphology of China can be divided into several parts. The historical centre of Chinese culture is on the loess plateau, the world's largest Quaternary loess deposit, and on the alluvial lands at the east of it. The alluvial East China plain extends from just south of Beijing in the north, to the Yangtze river delta in the south, punctuated only by the igneous Shandong highlands and peninsula. South of the Yangtze river, most of the landscape is mountainous, dominated by sedimentary deposits and by the South China Craton. The most famous scenery in China is found in the karst landscapes of Guangxi and Yunnan provinces. The alluvial Sichuan basin is surrounded by mountains, the Qinling mountains to the north and the Himalaya to the west and southwest. Much of Northeast China, or Manchuria, is dominated by alluvial plains, but the border regions with Korea are also highly mountainous. In the west, most of the Tibetan Plateau is in China, and averages over 4000 metres in elevation. The Yunnan-Guizhou plateau is also an extension of the Tibetan Plateau. Himalaya and Tibetan Plateau The Indian Craton has behaved like a near ridge block, moving north, and compacting the weaker, mostly sedimentary, rock into the Himalaya. Relative to a fixed Eurasian plate the central Himalaya and Tibetan Plateau are moving north (being pushed by India). The eastern half of the mountainous region is moving east away from India. The Tibetan Plateau is unstable and as its sides move away extension is occurring in its center. This east–west extension is accommodated on north–south trending normal faults. The Tian Shan are a mountain range north of the Tibetan Plateau and the Taklamakan Desert. Uplift of these mountains began