Complete Collection of Five Thousand Years of Geographic Mysteries in China - (Treasure Edition)

Author: Li Jin
Publisher:
Publish Date: 2006-07-01
Features: The Formation of the Sichuan Basin and the Extinction of Dinosaurs
It is not difficult to see from the three-dimensional map that the topography of the basin is not only shaped like a basin but also relatively round and very regular, with heights close to those of the surrounding mountains, presenting a generally higher elevation in the west and lower in the east. If there had never been the Sichuan Basin, the terrain in this area would have been an integral mountainous landscape similar to that of its surroundings, specifically: the west of the basin would have been the eastern arm of the Qinghai-Tibet Plateau, the north would have been the southern foothills of the Qinling Mountains, the south would have been the northern back of the Yunnan-Guizhou Plateau, and the east would have been the mountainous region adjacent to the western foothills of the Dabie Mountains. In this case, the entire western plateau would have originally been a complete entity, perfectly aligning with the logical principle—that energy equilibrium leads to shape equilibrium, while energy mutation leads to shape mutation. However, the actual formation of the Sichuan Basin occurred long ago. The massive stepwise changes in energy are manifested as regular abrupt variations in elevation within the basin. The significant alteration in topographic gradients caused by this sudden release of enormous energy can only be attributed to an asteroid impact. Moreover, before the asteroid impact, this area was the eastern edge of a vast expanse of highlands in central and western China. Therefore, the impact formed the Sichuan Basin and its surrounding topographic features. It is well known that the moon is dotted with numerous, varying-sized craters. Lunar craters are formed by the impact of extraterrestrial fragments (meteorites), a widely accepted fact. The lack of other mountains connected to the lunar craters beyond their periphery is clearly determined by the relatively flat surface of the moon. Thus, the dust stirred up by the impact force formed regular, ring-shaped craters distributed around the impact site. However, the asteroid that struck the Sichuan Basin did not land on a plain or in the ocean but precisely on a sloping terrain—the eastern edge of a massive, contiguous highland—the Sichuan Basin. Consequently, the craters formed by the impact could not resemble those on the moon but would instead resemble the topography of the Sichuan Basin and its surroundings. Ziyang is located in the middle of the Sichuan Basin and is the site where dinosaur fossils have been unearthed. Regarding the extinction of dinosaurs, paleontologists have proposed four hypotheses. Among them, the "asteroid impact theory" holds the most sway. P8