The study area covers the central part of the Great Lakes Basin in western Mongolia. A specific feature of the area is abundant evidence of large lakes existed there not long ago. That evidence consists of barrier beaches, terrace complexes, and large sand massifs. Remote sensing and field studies showed active tectonic processes within the Great Lakes Basin. Numerous paleoseismogenic deformations have been revealed along the periphery and in the water area of paleolake Hyargas Nuur, which was six times larger than the lake. The absolute heights of the maximum paleolake phase are 1143 m, which is 115 m higher than the present-day lake level. Tectonic movements led to the elevation of part of the former paleolake water area and barrier beaches to the absolute level of 1175 m. Landslides might have caused tsunami in the paleolake water area.