A Glacial Hypothesis
In the 1930s, the geologist J. S. Lee (Li Siguang) first proposed a startling idea: Lushan, a mountain massif in subtropical China, showed clear evidence of being carved by ancient glaciers during the Quaternary period. Lee identified a suite of classic glacial landforms across the mountain, whose highest peak, Hanyang, reaches 1,474 meters. His evidence included features he interpreted as U-shaped valleys, such as the Wangjiaopo Valley, and cirques, armchair-shaped hollows like the one at Da'ao. He also pointed to deposits of poorly sorted rocks and sediment as moraines and till, debris left behind by retreating glaciers.
Lee's hypothesis suggested that multiple glaciations had occurred here, far south of other known ice sheets in China. This interpretation became foundational to the study of Quaternary geology in the country. The "glacial relics" of Lushan are a main reason for its designation as a UNESCO Global Geopark, which promotes sites like the Wang Jia Po Glacial U-Valley and Da Ao Glacial Cirque. For decades, the glacial origin of Lushan's dramatic terrain was a widely accepted theory within China.
A Fluvial Counter-Argument
Despite its initial acceptance, the glacial hypothesis for Lushan has faced persistent scientific challenges. Many geologists now argue that the mountain's features are not the product of ice, but of tectonic uplift and persistent erosion by water—a process known as fluvial erosion. This alternative model suggests that so-called "U-shaped valleys" are actually structurally-controlled valleys, shaped by river systems cutting through the mountain's jointed sandstone bedrock.
Opponents of the glacial theory point to a lack of definitive evidence. For example, the deposits identified by Lee as moraines do not contain significant amounts of rock flour—the fine, silty powder created by glaciers grinding against bedrock. The boulders within these deposits also lack the distinct faceting and scratching (striations) that are characteristic signs of glacial transport. Instead, critics argue these deposits are better explained as fanglomerates, or consolidated debris flows, which are common in tectonically active mountain ranges. While the debate continues, this counter-argument suggests Lushan’s cliffs and deep valleys were carved not by ice, but by the relentless power of water and geology over millions of years.