Why is the small Tianchi Lake in Lushan Mountain a regular octagon?

Geological structure, water erosion and cultural factors.

1. Geological structure: Lushan Mountain is located in the volcanic active area, while Xiaotianchi Lake is located in the crater, forming a relatively flat basin surrounded by volcanic walls. This geological feature determines that the shape of Xiaotianchi is relatively regular and stable.

2. Water erosion: Lushan Mountain has a large amount of rainfall, and rainwater penetrates through mountain streams and groundwater to form a small Tianchi Lake. In a long time, the shape of the small Tianchi lake has gradually stabilized after erosion and erosion, showing a regular octagon.

3. Cultural factors: Xiaotianchi is endowed with cultural significance and aesthetic value. Eight is one of the auspicious numbers in China culture, symbolizing unity. Xiaotianchi is similar to the regular octagonal natural landscape, so it is also regarded as a symbol of good luck and beauty.