Wojciech Brochwicz-Lewinski, a member of the Polish team that researched the historic mound, told BNS that there are many places in the clay layer on the top of the hill that allow water to pass through.

"Water penetrates through the surface deep into the mound, which accelerates landslide formation," he said.

According to Brochwicz-Lewinski, water accelerates landslides, but there are many possible causes of landslides and each one may be caused by a different factor.