54 years ago today, April 29, 1971 (April 5, 1971, the lunar calendar), Li Siguang passed away. Li Siguang, a China geologist and founder of geomechanics, passed away on April 29, 1971. Li Siguang was born in 1889. From Huanggang, Hubei. After the founding of the People's Republic of China, he served as Vice Chairman of the National Committee of the Chinese People's Political Consultative Conference, Vice President of the China Academy of Sciences, and Leader of the Science and Education Group of the State Council. He gave a special report on "Vortex Structures and Other Composite Issues Related to the Northwest Geotectonic System" at the first meeting of the Geological Society of China. In addition, his arguments that the subsidence of the "Neocathaysian Structural System" in eastern China has good oil generation and reserve conditions have played a theoretical guiding role in exploiting oil and excavating mineral treasures in my country. His theoretical exposition on the geotectonic system has also been very effective in the occurrence laws of earthquakes and earthquake prediction in my country. The former Institute of Geology of the Academia Sinica, which was taken over by China Academy of Sciences, completed the geological map of Guangxi in January 1950. It is also the first geological map with the widest and most complete geological map in China that Li Siguang led to conduct investigation and editing in 1939 and took 6 years to complete. As early as the early 1920s, he investigated the coal-bearing strata of the Carboniferous and Permian Mountains in the north, and his research on the primary taxa of paleontology and the Tinco fossils of the Carboniferous and Permian Mountains gained international reputation. He successively discovered the remains of Quaternary glaciers in the foothills of the Taihang Mountains, Datong Basin, Lushan Mountain and Huangshan Mountain, effectively overturning the erroneous conclusion of many international glaciologists who asserted that there were no Quaternary glaciers in China. His main works include "The Main Causes of the Changes in the Image of the Earth's Surface","Tingke in Northern China","Geology of China","Lushan in the Ice Age","Introduction to Geomechanics","Seismic Geology", etc. Zhou Enlai and Li Siguang are together