Causes of land subsidence in the Kingdom of Saudi Arabia, 1997, Amin A, Bankher K,

The occurrence of land subsidence in the Kingdom Saudi Arabia is either natural or manmade. Natural land subsidence occurs due to the development of subterranean voids by a solution of host rocks in carbonate and evaporite terrains, over many areas of Saudi Arabia. Man-induced land subsidence is either due to the removal of groundwater in the agricultural areas or to wetting of unstable soils. Therefore, earth fissures and a lowering of the ground surface in unconsolidated sediments took place in alluvial plains and volcanic vent terrains. Unstable soils include Sabkha soils and loess sediments. These types of soils occur in coastal plains, desert areas and volcanic terrains. When this soil is wetted either during agricultural activities, waste disposal or even during a rain storm, subsidence takes place due to either the removal of salts from the Sabkha soil or the rearrangement of soil particles in loess sediments

THE LOESS “CAVE” NEAR THE VILLAGE OF SURDUK ¬AN UNUSUAL PSEUDOKARST LANDFORM IN THE LOESS OF VOJVODINA, SERBIA, 2009, Luki? Tin, Markovi? Slobodan B. , Stevens Thomas, Vasiljevi? Djordjije A. , Machalett Björn, Milojkovi? Nebojša, Basarin Biljana & Obreht Igor

Loess “caves” (piping caverns, wells, tunnels) exposed in loess cliffs are rare pseudokarst landforms that can be regarded as morphological equivalents to collapse dolines or sinkholes formed in classical karst terrains. This study presents the re¬sults of an investigation into a loess cave exposed in a loess cliff on the right bank of the Danube River near the village of Sur¬duk in the Vojvodina region, Serbia. This study provides a first detailed morphologic description of this young pseudokarstic landform formed by piping erosion, probably partly support¬ed with carbonate dissolution. The loess “cave” has a height of approximately 12 m and average diameter of around 3.5 m. In the middle of the cave ceiling there is a window. Observa¬tions indicate that over the last several years, the morphologi¬cal characteristics of the landform have been stable. The main aim of this study is to provide a better understanding of the evolution of the piping process in the thick loess-paleosol se-quences in the Vojvodina region, northern Serbia. A key role in the genesis of this landform was the short distance between an initial loess doline and a cliff exposing loess sediments, providing the possibility for the lateral removal of loess ma-terial. The presence of Robinia pseudoakacia trees around the initial depression modulated the evolution of the doline and provides support for the loess cavern roof. The nature of the dynamic erosional processes on the steep cliffs of the soft loess sediment indicates a very limited lifetime of this pseudokarstic landform.