Source of the photo
http://index.hu/belfold/2010/10/04/iszapomles_veszprem_megyeben/?p=0
Author of the description
Gruiz Katalin
You can see the broken dike on this picture. The dike might have possibly failed due to soaking and sliding of the underlying clayee soil.
Source of description
http://index.hu/belfold/2010/10/04/iszapomles_veszprem_megyeben/?p=0