CAUSES OF LAND SUBSIDENCE IN THE KINGDOM OF SAUDI-ARABIA

The occurrence of land subsidence in the Kingdom Saudi Arabia is eithe r natural or manmade. Natural land subsidence occurs due to the develo pment of subterranean voids by a solution of host rocks in carbonate a nd evaporite terrains, over many areas of Saudi Arabia. Man-induced la nd subsidence is either due to the removal of groundwater in the agric ultural areas or to wetting of unstable soils. Therefore, earth fissur es and a lowering of the ground surface in unconsolidated sediments to ok 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 eve n during a rain storm, subsidence takes place due to either the remova l of salts from the Sabkha soil or the rearrangement of soil particles in loess sediments.