الفهرس 
الخصائص الطبيعية العامة لمنخفض الفرافرةيوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Abstract
The study area occupies the eastern side of the Farafra depression in the Western desert of Egypt. The depression consists mainly of three major basins from east to west, namely: Farafra Basin, Basin of Wadi El Obiyad, and Basin of Ain Dalah. This study concentrates only on sand forms in Farafra Basin, which covers an area of 16,119.3 km². this depression extends between latitudes 25° 20ˋ N, 27° 45ˋ N and longitudes 27° 40ˋE, 30° 22 ˋ E. The depression is demarcated by clear scarps from the whole direction except from the south where it overlooks the Dakhla Depression. The total area covered by sand forms is estimated as 7000 km² or 68% of the depression’s total area.
This study falls into four chapters as follows: chapter one reveals the physical characteristics of the Farafra depression. It includes 1: the geological settings (rock successions, surficial deposits and rock structure), karst and solution processes, retraction of major scarps and residual forms (e.g. messa, inselbergs, towers, etc.), and climatic setting. Understanding the physical characteristics of the depression clarifies the role of the endogenic and exogenic agents in landform’s evolution. Hyper-arid dominant climatic condition in the Western Desert of Egypt makes it pertinent environment to strong wind activity.
Chapter two discusses the morphology of sand forms, which has been recognized as: barchan (crescent dunes), linear dunes (simple, compound, complex), transversed dunes, obstacle dunes, sand sheets and the micro- sand features as sand ripples and nebka. Spatial distribution of each sand form has been revealed in this chapter as well based on the analysis of satellite images. It has been deduced that transeversed and linear dunes are the most widespread sand forms in the Farafra Sand Sea, especially in the center and southern sectors where they intensively concentrate. Then, barchans dunes are the second widespread sand type. It is the most conspicuous sand form along the margins of the Farafra Sand Sea. On the other hand, micro- sand forms are found in the desert plains, interdune area, between the karstic forms in the White Desert. The most morphological characteristic of the dominant sand forms were also clarified in this chapter.
Chapter three clarifies the physical characteristics of sand grains in the study area as mechanical analysis, micro features on the grain surface, and mineral analysis. The study cleared that medium sand size is the most common, and then comes the fine sands and coarse sands. Based on the correlation matrix, correlation between grain size and sand forms differs from one form to another. However, size, skew and kurtosis reveal weak inversed relationship as most of the grain size lies in the mean kurtosis. The grains were greatly influenced by mechanical wind action and with a lesser degree by chemical action as stated from the micro-surface features e.g. plates, inverted plates, linear depression, arc and linear lichens, irregular grain forms and silica deposits.
Mineral analysis clarifies that non-opaque minerals are the most common heavy minerals with 63.41%, while opaque minerals constitute 36.59%. The major common non-opaque minerals are zircon, abidoye, pyroxene, garnet, and amphibole respectively.
Chapter four revealed the imperative problems owing to sand encroachment in the study area. This problems could be enumerate as: 1. sand drift over agriculture lands and irrigation wells and channels in Kefah and Abu Hurayira villages, Western of El Qasr and Mawhoub, Karaween Plain, Wells of Gafreen, Well of Marzouq, Well of Shamanda, etc. 2. Sand drift on settlements as stated in villages of Kefah, Abu Hurayira, Abu Minqar, and talaat Dorgham. 3. Sand drift on roads such as El Farafra-Abu Minqar road, El Farafra-El Baraka Plain road, El Farafra-Baharyia road. Factors affecting sand movements were also discussed in this chapter. It has been concluded that the problem is primarily due to expansion of land reclamation and human settlement in areas that is already prone to sand movement.