Wikipedia
Xirang , also known as Swelling Earth, is a magical substance in Chinese mythology that had a self-expanding ability to continuously grow- which made it particularly effective for use by Gun and Yu the Great in fighting the rising waters of the Great Flood. This Chinese word compounds xī "breathe; cease; rest; grow; multiply" and rǎng "soil; earth". Noting similarities with earth-diver creation myths, Anne Birrell translates xirang as "self-renewing soil", and compares other translations of "breathing earth" ( Wolfram Eberhard), "swelling mold" ( Derk Bodde), "idle soil" (Roger Greatrex), and "living earth" or "breathing earth" (Rémi Mathieu).
In some versions of the myths, Gun stole the xirang from the Shangdi, who sent Zhu Rong to execute him in punishment, on Feather Mountain. According to some accounts, Yu, on the other hand, went up to Heaven. After begging Shangdi, he received from him a gift of as much xirang as his magical black tortoise could carry on its back, thus allowing Yu to successfully block up the 233,559 springs, the sources of the flood waters. In other versions of these myths, xirang was stolen or obtained from the Primordial Divinity, or Gun's executioner was other than Zhu Rong.
A historical basis has been suggested for both the Great Flood and for xirang. Hawkes proposes that the myths are a symbolic interpretation of a societal transition. In this case, Gun represents a society at an earlier technological stage, which engages in small scale agriculture which involves raising areas of arable land sufficiently above the level of the marshes. The "magically-expanding" xirang soil may represent a type of raised garden, made up of soil, brushwood, and similar materials. Yu and his work in controlling the flood would symbolize a later type of society, which allowed a much larger scale approach to transforming wetlands to arable fields.