This paper seeks to investigate the properties of volcanic soil from the Aratozawa landslide, the largest failure triggered by the 2008 Iwate-Miyagi Nairiku earthquake, Japan. Field investigation was carried out to estimate the in-situ characteristics of volcanic material. It was found that the soil was highly weathered, having low dry density and high moisture content. Laboratory examination included a series of triaxial compression tests which were performed to evaluate the dynamic properties of volcanic soil. Results of undrained cyclic loading tests indicated that the material had a high potential for generation of excess pore-water pressures, which could lead to a significant loss of strength during earthquake loading. This finding suggests that liquefaction might have occurred in the weathered mass of volcanic rocks during the earthquake, initiating the failure. Based on the results of this study, the role of volcanic soil in the slide development was determined.