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35-524: Since 2001, the Nubian Sandstone aquifer situated between the Toshka and Abu Simbel areas of Egypt has undergone intensive drilling and development as part of a land reclamation project. Drilling information was used to conduct a variety of studies regarding the hydrogeological setting of the area's aquifer. Results indicated that lithological characteristics and tectonic settings are having

70-511: A break in rainfall during mid-season when the Intertropical Convergence Zone or monsoon trough moves poleward of their location during the middle of the warm season; Typical vegetation in these areas ranges from moist seasonal tropical forests to savannahs . When the wet season occurs during the warm season, or summer , precipitation falls mainly during the late afternoon and early evening hours. The wet season

105-478: A connection between the spatial organization of fluvial and structural features with low- salinity groundwater, which exists adjacent to alluvial fans and the south-west reaches of structurally enclosed channels. Wells in the vicinity of structures contained low-salinity water. Nubian Sandstone exposures in sub-humid, semi-arid, and arid conditions produce soil that is red and sandy but very different in other aspects. Only in sub-humid zones do these soils contain

140-581: A lengthy duration of water residence. Two recharge locations have been identified by Reika Yokochi et al.: one 38,000 years ago originating from the Mediterranean, and the second dated at around 361,000 years ago from the tropical Atlantic. Since 2006, the International Atomic Energy Agency has been working in cooperation with the four NSAS countries to help increase understanding of the aquifer's complexities through

175-459: A moderately developed profile, including a textural B horizon lacking soluble salts and carbonates . In semi-arid and arid zones, profile differentiation is either weak or does not exist. In arid zones soils are shallow and contain carbonates, and soluble salts, including gypsum . The sole clay mineral common to all Nubian sandstone parent materials is kaolinite , which is the major clay mineral in sub-humid zone soil. In semi-arid soils smectite

210-596: A much wider variety of color. The ancient temples and tombs in Petra were carved from this rock. In certain places it is extremely friable , and in others compact and hard. Sand in the Arabian deserts was primarily derived from it, carried by prevailing western winds. Where it is covered by a sheet of eruptive rock ( charrah ), it is protected from erosion . Nubian Sandstone frequently includes strata of clay and shale and thin seams of coal or lignite . This indicates that it

245-527: A substantial effect on groundwater flow patterns and the area's overall aquifer potentiality, which is considered relatively low when compared to neighboring areas in eastern Oweinat or Dakhla . The aquifer is largely composed of hard ferruginous sandstone with great shale and clay intercalation , having a thickness that ranges between 140 and 230 meters. Groundwater type varies from fresh to slightly brackish ( salinity ranges from 240 to 1300 ppm ). The ion dominance ordering shows that sodium cation

280-466: Is a second major clay component. In arid zones small amounts of smectite and palygorskite accompany kaolinite. It is likely that smectite and palygorskite are products of pedogenic neoformation. Aeolian material was probably introduced into the silt and fine sand fractions from semi-arid and arid soils. It is also possible that some contamination of clay fractions occurred. When in contact with Upper Cretaceous limestone , Nubian Sandstone underlies

315-500: Is a time when air quality improves, freshwater quality improves and vegetation grows significantly due to the wet season supplementing flora, leading to crop yields late in the season. Floods and rains cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients are washed away and erosion increases. The incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for

350-441: Is most commonly predominating over calcium and magnesium – whereas chloride is predominant over sulfate and bicarbonate . The groundwater is of meteoric origin (the term meteoric water refers to water that originated as precipitation; most groundwater is meteoric in origin). High concentrations of sodium, chloride, and sulfates reflect the leaching and dissolution processes of gypsiferous shales and clay, in addition to

385-585: Is that the tropics represent a ' Garden of Eden ', a heaven on Earth, a land of rich biodiversity or a tropical paradise. The alternative is that the tropics consist of wild, unconquerable nature. The latter view was often discussed in old Western literature more so than the first. Evidence suggests over time that the view of the tropics as such in popular literature has been supplanted by more well-rounded and sophisticated interpretations. Western scholars tried to theorise why tropical areas were relatively more inhospitable to human civilisations than colder regions of

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420-605: The Andes as far south as the northernmost parts of Chile and Perú . The climate is changing in the tropics, as it is in the rest of the world. The effects of steadily rising concentrations of greenhouse gases on the climate may be less obvious to tropical residents, however, because they are overlain by considerable natural variability. Much of this variability is driven by the El Niño-Southern Oscillation (ENSO) . The Tropics has warmed by 0.7–0.8 °C over

455-701: The Carboniferous to Lower Cretaceous . The Nubian Sandstone ranges in age from the Cambrian to Upper Cretaceous eras. Positioning of the paleoequator and paleolatitude at 20° S was derived from paleomagnetic data showing the Nubian was originally deposited in the paleoequatorial to subequatorial zone. These paleomagnetic results corroborated previous studies suggesting that north Africa did not shift in latitude from 210 to 110 million years ago and extended this period to 85 million years. Nubian Sandstone

490-732: The Pantropic . The system of biogeographic realms differs somewhat; the Neotropical realm includes both the Neotropics and temperate South America, and the Paleotropics correspond to the Afrotropical , Indomalayan , Oceanian , and tropical Australasian realms . Flora are plants found in a specific region at a specific time. Some well-known plants that are exclusively found in, originate from, or are often associated with

525-579: The Waterberg Biosphere of South Africa , and eastern Madagascar rainforests. Often the soils of tropical forests are low in nutrient content, making them quite vulnerable to slash-and-burn deforestation techniques, which are sometimes an element of shifting cultivation agricultural systems. In biogeography , the tropics are divided into Paleotropics (Africa, Asia and Australia) and Neotropics (Caribbean, Central America, and South America). Together, they are sometimes referred to as

560-719: The axial tilt of the Earth . The Tropic of Cancer is the Northernmost latitude from which the Sun can ever be seen directly overhead , and the Tropic of Capricorn is the Southernmost. This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year . Thus the maximum latitudes of the tropics have equal distances from the equator on either side. Likewise, they approximate

595-712: The Ain Dalla basin, a downthrown structural block south-west of the Bahariya oasis. Basement features present a dominant control on the complex's structural and sedimentological form. Despite many structural complications, the Nubian Sandstone likely constitutes a single hydrogeological system west of the Suez Gulf . To the east, on the Sinai Peninsula , a second system might exist with some connection to

630-669: The IAEA-UNDP-GEF Nubian Project. Project partners include the United Nations Development Programme ( UNDP )/ Global Environment Facility ( GEF ), IAEA, United Nations Educational, Scientific and Cultural Organization ( UNESCO ) and government representatives from the NSAS countries. The project's long-term goal is establishing rational and equitable management of the NSAS as a productive way of advancing socio-economic development in

665-677: The Nubian Sandstone is relatively simple in Lebanon, Anti-Lebanon and Hermon, it is much more complicated in Western Sinai and the Dead Sea area. Since sandstone is assumed to form more rapidly than other rocks it is difficult to conceive that the 2,000 feet of sandstone in the southeastern Dead Sea was in the formative process from the Cambrian to the Cretaceous. Nubian Sandstone is most commonly brown or reddish, but in places it shows

700-399: The angle of the Earth's axial tilt. This angle is not perfectly fixed, mainly due to the influence of the moon, but the limits of the tropics are a geographic convention, and their variance from the true latitudes is very small. Many tropical areas have both a dry and a wet season. The wet season , rainy season or green season is the time of year, ranging from one or more months when most of

735-459: The average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics , some even in temperate regions. Under the Köppen climate classification , for tropical climates , a wet-season month is defined as one or more months where average precipitation is 60 mm (2.4 in) or more. Some areas with pronounced rainy seasons see

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770-507: The desert in western Egypt was induced by fluvial action, including recently mapped alluvial fans . In central areas, braided channels are spatially aligned to a north-east structural trend, suggesting preferential water flow paths. Alluvial fans and structurally enclosed channels with gentle slopes and optimal recharge conditions between 1 and 5%, indicating high groundwater potential. Synthetic Aperture Radar (SAR) interpretations correlated with anomalies from groundwater in 383 wells, suggest

805-460: The geographic region; these usages ought not be confused. The Earth's axial tilt is currently around 23.4° , and therefore so are the latitudes of the tropical circles , marking the boundary of the tropics: specifically, ±23°26′09.8″ (or 23.43605°). The northern one is called the Tropic of Cancer , and the southern is the Tropic of Capricorn . As the Earth's axial tilt changes, so too do

840-961: The last century—only slightly less than the global average—but a strong El Niño made 1998 the warmest year in most areas, with no significant warming since. Climate models predict a further 1–2 °C warming by 2050 and 1–4 °C by 2100. Tropical plants and animals are those species native to the tropics. Tropical ecosystems may consist of tropical rainforests , seasonal tropical forests , dry (often deciduous) forests , spiny forests, deserts , savannahs, grasslands and other habitat types. There are often wide areas of biodiversity , and species endemism present, particularly in rainforests and seasonal forests. Some examples of important biodiversity and high-endemism ecosystems are El Yunque National Forest in Puerto Rico , Costa Rican and Nicaraguan rainforests, Amazon Rainforest territories of several South American countries, Madagascar dry deciduous forests ,

875-558: The latter conformably. In Lebanon , Anti-Lebanon and Hermon it is underlain by Jurassic limestone. Its upper strata is likely from the Lower or Middle Cretaceous age. However, Jurassic limestone is absent in southern areas. In Western Sinai , Nubian Sandstone rests on Carboniferous limestone, and by the Dead Sea on Cambrian limestone: at Petra and other locations it rests unconformably on crystalline rocks . While age calculation for

910-719: The overhead sun, the tropics receive the most solar energy over the course of the year, and consequently have the highest temperatures on the planet. Even when not directly overhead, the sun is still close to overhead throughout the year, therefore the tropics also have the lowest seasonal variation on the planet; "winter" and "summer" lose their contrast. Instead, seasons are more commonly divided by precipitation variations than by temperature variations. The tropics maintain wide diversity of local climates, such as rain forests , monsoons , savannahs , deserts , and high altitude snow-capped mountains . The word "tropical" can specifically refer to certain kinds of weather , rather than to

945-477: The primary western system in the north. The main western system, extending into Libya and Sudan , consists of a multi-layered artesian basin where massive groundwater reserves accumulated, principally during pluvials of the Quaternary . Locally, carbonate rocks overlying complex karst features and are recharged from the underlying major aquifer . Fluvial and structural interpretations from 2007 show

980-593: The region and protecting biodiversity and land resources. Nubian Sandstone The Nubian Sandstone is a variety of sedimentary rock deposited on the Precambrian basement in the eastern Sahara , north-east Africa and Arabian Peninsula . It consists of continental sandstone with thin beds of marine limestones , and marls . The Nubian Sandstone was deposited between the Lower Paleozoic and Upper Cretaceous , with marine beds dating from

1015-521: The regions of Earth surrounding the Equator , where the sun may shine directly overhead . This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's axial tilt ; the width of the tropics (in latitude) is twice the tilt. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone ). Due to

1050-516: The tropical and polar circles . The tropics constitute 39.8% of Earth's surface area and contain 36% of Earth's landmass . As of 2014 , the region was home also to 40% of the world's population , and this figure was then projected to reach 50% by 2050. Because of global warming , the weather conditions of the tropics are expanding with areas in the subtropics , having more extreme weather events such as heatwaves and more intense storms. These changes in weather conditions may make certain parts of

1085-469: The tropics include: Tropicality refers to the image of the tropics that people from outside the tropics have of the region, ranging from critical to verging on fetishism. Tropicality gained renewed interest in geographical discourse when French geographer Pierre Gourou published Les pays tropicaux ( The Tropical World in English), in the late 1940s. Tropicality encompassed two major images. One,

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1120-568: The tropics uninhabitable. The word "tropic" comes via Latin from Ancient Greek τροπή ( tropē ), meaning "to turn" or "change direction". The tropics are defined as the region between the Tropic of Cancer in the Northern Hemisphere at 23°26′09.8″ (or 23.43605°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′09.8″ (or 23.43605°) S; these latitudes correspond to

1155-726: The wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature. However, regions within the tropics may well not have a tropical climate. Under the Köppen climate classification, much of the area within the geographical tropics is classed not as "tropical" but as "dry" ( arid or semi-arid ), including the Sahara Desert , the Atacama Desert and Australian Outback . Also, there are alpine tundra and snow-capped peaks, including Mauna Kea , Mount Kilimanjaro , Puncak Jaya and

1190-585: Was deposited in seas that were relatively shallow at the time. The term Nubian Sandstone was first introduced to the Egyptian stratigraphy by Joseph Rüssegger in 1837, who used the term "Sandstein von Nubien" to designate nonfossiliferous sandstone sections of Paleozoic or Mesozoic age. Rüssegger followed and studied this series of sandstone formations from the Sudan , Egypt , Libya , and Arabia Petrsea (northeastern Arabia). Tropical The tropics are

1225-451: Was deposited under a tropical to subtropical climate and formed under a variety of continental conditions, including eolian merging intermittently into shallow marine. The Nubian Sandstone complex has a thickness varying from under 500 m to over 3000 m, resting on the Precambrian basement . This is complicated by various structural faults and fold axes traversing the region in a north-eastern direction. Maximum development occurs in

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