Abstract: Landslides initiated near the ridge of a high and steep slope result in a volley fall,characterized by high speed,large hazard areas,and tremendous destruction. They pose immense danger to the infrastructure,human lives,and properties. For example,consider the Xiongershan landslide that occurred on February 7,2023 in the Li county,Sichuan province. The elevation of the crown of the landslide was 2413 m and that of the front edge was~1595 m. The height difference of the landslide was 818 m,and the horizontal distance was 1085 m. The landslide disintegrated and transferred into avalanche debris and rock fall,resulting in the interruption in communication and transportation infrastructures. Based on site investigation,unmanned aerial vehicle photogrammetry,and satellite-image interpretation,this study provides a detailed description of the characteristics and analysis of the failure mechanism of the landslide. The results reveal an approximately 15-years progressive deformation process of the source area of the landslide. The Wenchuan earthquake in 2008 resulted in the formation of fissures and cracks in the slope,which are highly favorable for precipitation infiltration and cause the deterioration of soil masses on the slope. The continuous dry-wet cycle,experienced from 2008 to 2022,resulted in slope deformation and induced a retrogressive failure process of the landslide. Finally,the deformation of the source area of the landslide accelerated during the rainy season of 2022,subsequently resulting in the occurrence of a landslide on February 7,2023. This event caused a slide of approximately 6×10⁴ m³ of soil mass,some of which exited from the source area and transferred into a dry debris slide. The landslide mass eventually deposited on a relatively gentle slope with an average slope gradient of approximately 31°. However,some of the boulders that crossed the accumulation area and entered a steep slope below,formed a large-area rockfall. Therefore,the final landslide area measured 66 times that of the source area. This case study indicates that the landslides that occur on the high and steep slopes may have a long-term prefailure evolution process and could form large-scale disaster chains. Therefore,periodic investigations along important traffic lines are crucial for the early identification and prevention of landslides on high and steep slopes.