The landform and kinematics characteristics of Mahu ancient landslides in Leibo County,Sichuan Province were analyzed in detail to obtain it’s causes aimed at the new finding of it’s scale.Analysis on the riverbed of ancient Huanglang River,the plane range and depth of the ancient landslide was done on the basis of borehole and ultrasonic measurement of the terrain of the dammed lake bottom.Based on the site investigation of shape,structure and geological environment,the landform was analyzed,the periodizations of the landslides were described,and the movement of each landslide event was concluded.The energy conservation equation was used to calculate the velocity,which helps to confirm the causes of the ancient landslides.The results showed the landslide has a super large-scale,with surface area of 18.2 km2which includes the underwater part and volume of about 20×108m3.The ancient landslides can be divided into three zones according its composition and four events according its order.The landslide slided along the high and steep formation interface with huge scale,huge velocity and longer distance,it may be caused by earthquake;analysis of the landform and kinematics of ancient landslides is a good method to help confirming their causes.
