Some Geological Hazards in Egypt, Their Nature and Extent

The present paper deals with the geological investigation of the sites susceptible to natural hazards in Egypt. Earthquakes, landslides, and the movement of sand dunes are the most important events causing future disasters. Dealing with the earthquakes, Egypt is a country of low to moderate seismic hazard and earthquakes are active in the northern parts of the country and along the western side of the Red Sea. In the northern parts the dominant rock types are related to the Oligocene, and along the western side of the Red Sea coast the land is covered by the Quaternary deposits. Correlating the seismicity with large — scale tectonic features such as faults, it was found that NNW and E — W faults are responsible for some significant seismic activity. The areas with relatively low seismic activity are covered by thick marine limestone of Cretaceous age lying above the Nubian sandstone in the larger part of the Western Desert. The basement rocks in the Eastern Desert have also low seismic activity The Nile Valley and Delta areas are underlain by thick alluvial sequences that are likely to provide a much less secure foundation during earthquakes than the crystalline bedrock in the Eastern Desert. Damage to buildings is related to clay thickness. Clays swell and slake in water leading to vulnerability of the buildings in areas with considerable clay thickness.The poor mechanical properties and structural of most geological formations, the seismic characteristics of the territory, the intense rainfall as well as the human activities are the main causes of landslide. On the other hand, vast areas in the Western Desert is covered by moving sands which can be considered an important event in natural disaster. Sand dunes to the north of the Nile Delta started to encroach the cultivated land. To avoid dune movement over areas of future development, the location should be proportional to the rate of barchan movement.