Gediminas’s Castle Hill (in Vilnius) Case: Slopes Failure Through Historical Times Until Present

Abstract

The remaining buildings of Gediminas’s Castle in Vilnius stand on the top of a 40 m high hill composed of Quaternary glacial, glaciolacustrine, glaciofliuvial inter-layered deposits and technogenic (cultural layer) accumulations. The city center and castles are located in an area at the very margin at the maximum advance of the Weichselian glaciation. There was no direct erosion impact in the area of Vilnius’s hills from meltwater for the formation of the upper reaches of the highest ravines. Therefore, it is proposed that the main features of the Vilnius Castles hills were formed by periglacial thermal erosion—the movement of land masses due to the thawing of permafrost at a time of climate change and the beginning of the vanishing of the Weichselian ice body. Over the course of history people reshaped the slopes of these hills for living and defense purposes. The saddle connecting Gediminas’s Hill and the massif of the Hill of Three Crosses goes back to historical times when the artificial channel for the Vilnia River was dug and it became a separate hillfort. Due to the steep slopes of the hills, slope deformations and landslides have been occurring since the historical past until the present. Recently a landslide formed on the eastern slope in 2004 and reactivated in 2008. In early spring of 2016 two new landslides appeared on the northwestern slope preceded by a number of cracks on the ground surface. Causes of slopes failure and general problems of stabilization are dealt with this article, also covered is the necessity of early warning system installation, slopes surfaces permanent monitoring based on 3D laser scanning, etc.