In other areas, especially in Farasan Al-Kabir, long narrow ravines have developed due to the leaching of salt substratum and the collapse of overlying coral surfaces. These ravines are about 50 ft. deep and possess a sizable portion of the floral components, mostly ephemerals. Generally islands consist of uniform reef flat that are underlain by bright white marly limestones. Farther down, these are replaced by yellow-green sequences with isolated clay interlayers. An overall evaluation of the Farasan archipelago, particularly in Farasan Al-Kabir and Sajid, shows that the area has numerous faults and fault bundles. Though there are various speculations about the development of these fault structures, the present day fracturing of the area is apparently due to the ascending salt and so in part to the associated gravitational sliding process.  The general topography of other islands such as Zifaf, Dawshak, Dumsuq, etc. are also more or less same as that of Farasan Al-Kabir. However, in Zifaf, the fossil coral is in the form of ridges and folds with a number of wadis.

                         The studies on the flora of Farasan archipelago and various plant communities are of great significance in scientific research as the species occur in an independent environment where influences from other similar communities found in the mainland are almost nil. Presently, Farasan Al-Kabir is a protected area because of the presence of the only remaining wild population of Arabian Gazelle. These islands also play an important role for migratory birds as a nesting place and for developing a conduce environment for a number of endemic races of snakes. However, the first and foremost important factor that makes Farasan group of islands unique is the presence of two important Mangrove populations, Avicennia marina and Rhizophora mucronata. These species are ecologically important and highly productive littoral biotopes and are acting as a reservoir and refuge for many small animals, birds and fish. The pneumatophores that grow erect above water are an ideal site for the breeding of a number of fish, particularly of shrimps, prawns and crabs. Both species share the same shore-line habitat and seen growing side by side. Though intermixed with each other, Rhizophora mucronata can be easily told apart from the other by its shiny, dark green leaves. 

Climate

                        There are no weather stations located in any part of the archipelago. The climatic data is, therefore, collected from Jizan meteorological station. Similar to the climate of Tihama region in the mainland, all islands are also generally dry with unpredictable rain. The data recorded from 1985 to 1998 shows that the highest average precipitation was reported in December and the highest average temperature was in the months of June and August.

Vegetation

                                       Occasional rains, condensation of dews or underground water sources are the main influential factors for the growth of annual vegetation in these islands. The highest concentration of the vegetation is seen in the sheltered wadis with fine silty-clay. The southeastern area of Farasan Al-Kabir, where the land is rugged, contains the highest number of plant species whereas the northwestern unbroken plateau and the western facing shoreline are devoid of plants except for a few annual species. Among the higher plants, a considerable number of them are halophytes or semi-halophytes and the growth of these plants is influenced by the salinity of the soil and the proximity to the seashore. Vegetation along the shoreline of Farasan and Sajid islands, particularly along the inlets and bays is dominated by Avicennia marina whereas in Zifaf and Dumsuq islands another mangrove, Rhozophora mucronata, also show its presence along with Avicennia marina.

                             Vegetation in the sandy beaches is dominated, mainly, by halophytes such  as Limonium axillare, Suaeda monoica, Halopeplis perfoliata, Zygophyllum ssp., Aeluropus lagopoides, Cress cretica, etc. On the basis of habit and degree of grazing pressure by wild and domestic herds, communities of Euphorbia fractiflexa, Panicum turgidum, Commiphora opobalsamum, Acacia ehrenbergiana, Blepharis ciliaris, Zygophyllum simplex, Salvadora persica, etc. are developed in almost all major islands (Alwelaie et al., 1993).

List of species belonging to the flora of Saudi Arabia that are collected from Farasan Archipelago only.

Basilicum polystachion (L.) Moench                            Labiatae

Cleome noeana ssp. brachystyla Chamberlain & Lamond  Capparaceae

Commiphora erythraea (Ehrenb.) Engl.                        Burseraceae

Dinebra retroflexa (Vahl) Panzer                                 Gramineae

Drake-brockmania somalensis Stapf                            Gramineae

Ficus populifolia Vahl                                                 Moraceae

Glossonema sp. aff. boveanum (Decne.) Decne.          Asclepiadaceae

Indigofera semitrijuga Forssk.                                     Leguminosae

Ipomoea hochstetteri House                                         Convolvulaceae

Limonium cylindrifolium (Forssk.) Verdc.                     Plumbaginaceae

Micrococca mercurialis (L.) Benth.                             Euphorbiaceae

Nothosaerva brachiata (L.) Wight                               Amaranthaceae

Taverniera cuneifolia (Roth) Arn.                                Leguminosae

Vahlia digyna (Retz.) Kuntze                                       Vahliaceae

Following is list of sea grasses occurring in the shallow waters of various islands.

Cymodocea sp. (?rotundata)             (Cymodoceaceae)    - As-Sajid island               

Halophila ovalis R. Brown               (Hydrocharitaceae)  -  Farasan Al-Kabir and Zifaf islands

Thalassia hemprichii (Ehr.) Aschers  (Hydrocharitaceae)  - Farasan Al-Kabir island

Thalasia testudinum Koenig et Sims  (Hydrocharitaceae)  -  Zifaf island    

(Courtesy: An outline of the flora of Farasan Archipelago, South Red Sea  by  Dr. Ahmed H. Alfarhan, Dr. Turki A. Al-Turki, Dr. Jacob Thomas & Mr. R. A. Basahy)