The formation of plaster comes from the grinding of ancient glacial meltwater. 5-2 million years ago, the earth entered the Quaternary glacial period, and the climate was extremely cold. Many parts of the world, including the North Sea, are covered by glaciers one to several kilometers thick. With the warming of the climate, glaciers began to melt slowly, and a large amount of glacier melt water (including pressure melt water below 0℃ and glacier melt water above 0℃) flowed down the glacier cracks, forming a vortex under the glacier, impacting and grinding the rocks under the glacier with ice debris.
In China, the mortar was first discovered in 1970s. At that time, there were only sporadic records in Huangshan, Lushan and Tibet, and there were only records in northern Europe, North America and Antarctica in the world. China's original research on mortar originated in the west, and its original translation was called mortar. A large number of mortar discoveries in China began at 1997, and distributed from the northern country with high latitude to Guangdong and Hainan Island with low latitude, indicating that the whole country was covered by glaciers during the ice age.
The mortar found in China mainly includes Daqingshan in Keshiketeng Banner, Jiufoshan in Chifeng City, Inner Mongolia, Jiulong Cave in Fujian, Zhongyuan in Jing 'an County, Jiangxi suichuan county, Beijing in Yanqing County, and Jianban Ancient Town in Leshan City, Sichuan Province.
The mortar group of Dalian Mountain in the North Sea is composed of three or more relatively close mortars, which fills the blank of mortar geological phenomenon in the coastal area of Beibu Gulf in southern Guangxi.