|Waw an Namus|
|Wau-en-Namus, Uau en Namus, Waw an Namous|
The central cone of Waw an Namus
|Elevation||547 metres (1,795 ft)|
|English translation||Oasis of mosquitoes|
|Age of rock||Pleistocene|
Waw an Namus (also spelled Wau-en-Namus, Arabic : واو الناموس) is a volcano in Libya. Of either Pleistocene or Holocene age, it is located within the eastern Fezzan region. The origin of the volcanism there and at Al Haruj farther north is not clear. Radiometric dating has yielded an age of about 200,000 years, but other circumstantial evidence points to a formation of the volcano during Holocene or even historical times.
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
Libya is a country in the Maghreb region in North Africa, bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad to the south, Niger to the southwest, Algeria to the west, and Tunisia to the northwest. The sovereign state is made of three historical regions: Tripolitania, Fezzan and Cyrenaica. With an area of almost 1.8 million square kilometres (700,000 sq mi), Libya is the fourth largest country in Africa, and is the 16th largest country in the world. Libya has the 10th-largest proven oil reserves of any country in the world. The largest city and capital, Tripoli, is located in western Libya and contains over one million of Libya's six million people. The second-largest city is Benghazi, which is located in eastern Libya.
The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.
Waw an Namus is characterized by a caldera surrounded by an apron of dark tephra, which has a notable colour contrast to the surrounding desert terrain of the Sahara. A smaller crater lies northwest of the Waw an Namus caldera. The caldera itself contains a scoria cone. Several small lakes and associated vegetation are located within the caldera.
A caldera is a large cauldron-like hollow that forms right after the eruption of a volcano and the release of a magma chamber/reservoir. When large volumes of magma are erupted over a short time, structural support for the crust above the magma chamber is lost. The ground surface then collapses downward into the partially emptied magma chamber, leaving a massive depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven known caldera-forming collapses have occurred since the start of the 20th century, most recently at Bárðarbunga volcano in Iceland.
Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism.
A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one-third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.
The volcano is also known as Uaw en Namus,Uau en Namus, Wau-en-Namus and Wau Sqair. It means "oasis of mosquitoes", a reference to the small lakes around it and the numerous mosquitoes that exist at Waw an Namus, nurtured by the lakes at the volcano.
In geography, an oasis is the combination of a human settlement and a cultivated area in a desert or semi-desert environment. Oases also provide habitat for animals and spontaneous plants.
Mosquitoes are a group of about 3500 species of small insects that are a type of fly. Within that order they constitute the family Culicidae. The word "mosquito" is Spanish for "little fly". Mosquitoes have a slender segmented body, a pair of wings, three pairs of long hair-like legs, feathery antennae, and elongated mouthparts.
The volcano lies within the Sahara, in the eastern Fezzan and was discovered a few decades before 1951.The caravan route between Kufra and Sebha passes by the volcano. Ancient graves have been found at Waw an Namus. While the oasis was probably visited by herders and hunters and may have been the source of raw materials, the place is otherwise uninhabited. The landscape around Waw an Namus has been described as "very beautiful" but logistical issues and the Libyan Civil War make it difficult to access the area.
The Sahara is a desert located on the African continent. It is the largest hot desert in the world, and the third largest desert overall after Antarctica and the Arctic. Its area of 9,200,000 square kilometres (3,600,000 sq mi) is comparable to the area of China or the United States. The name 'Sahara' is derived from a dialectal Arabic word for "desert", ṣaḥra.
Fezzan is the southwestern region of modern Libya. It is largely desert, but broken by mountains, uplands, and dry river valleys (wadis) in the north, where oases enable ancient towns and villages to survive deep in the otherwise inhospitable Sahara Desert. The term originally applied to the land beyond the coastal strip of Africa proconsularis, including the Nafusa and extending west of modern Libya over Ouargla and Illizi. As these Berber areas came to be associated with the regions of Tripoli, Cirta or Algiers, the name was increasingly applied to the arid areas south of Tripolitania. Fezzan is Libya’s poorest region.
A caravan is a group of people traveling together, often on a trade expedition. Caravans were used mainly in desert areas and throughout the Silk Road, where traveling in groups aided in defense against bandits as well as helping to improve economies of scale in trade.
Waw an Namus is a 100-metre-deep (330 ft), 4-kilometre-wide (2.5 mi) caldera, which has a small relief outwards but a steep margin inwards. During its formation, over 800,000,000 cubic metres (2.8×1010 cu ft) of rock were displaced. Another crater lies 5 kilometres (3.1 mi) northwest from Waw an Namus. That vent was formed by overlapping craters which feature no volcanic rocks and which have produced salty mud; this may have been a site of phreatic activity and of volcanic degassing. The caldera contains ash deposits and some dunes, but also a humid zone with reeds.
Phreatic is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to eruption type.
In physical geography, a dune is a hill of loose sand built by aeolian processes (wind) or the flow of water. Dunes occur in different shapes and sizes, formed by interaction with the flow of air or water. Most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter "slip face" in the lee side. The valley or trough between dunes is called a slack. A "dune field" or erg is an area covered by extensive dunes.
Reed is a common name for several tall, grass-like plants of wetlands.
Within the caldera lies a 140-metre-high (460 ft), 1.3-kilometre-wide (0.81 mi) scoria cone constructed out of phreatomagmatic material with an 80-metre-deep (260 ft), 150-metre-wide (490 ft) crater. Another crater, now reduced to remnants, is located west of the summit crater of the cone. The cone has been modified by gullies.
A volcanic crater is an approximately circular depression in the ground caused by volcanic activity. It is typically a bowl-shaped feature within which occurs a vent or vents. During volcanic eruptions, molten magma and volcanic gases rise from an underground magma chamber, through a tube-shaped conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted as lava. A volcanic crater can be of large dimensions, and sometimes of great depth. During certain types of explosive eruptions, a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger depression known as a caldera.
Dark-coloured tephra of basaltic composition has buried the desert sand around the caldera to distances of 10–20 kilometres (6.2–12.4 mi), resulting in a conspicuous colour contrast to the much brighter desert sand. This contrast can be noted even on spaceborne images. The tephra deposit consists of volcanic ash and lapilli and covers a surface of about 300 square kilometres (120 sq mi). 2–150-centimetre-high (0.79–59.06 in) waves are formed by the tephra, which in its western part is baked together by mudflows. The tephra deposit is stratified, implying that it was generated by more than one eruption. Trade winds have blown the tephra over 100 kilometres (62 mi) southwestward, and a large number of megaripples formed by volcanic material occur both inside and outside of the caldera.
Also within the caldera are three small lakes 0.3 square kilometres (0.12 sq mi) and the largest lake has a surface area of 0.146 square kilometres (0.056 sq mi) with a depth of 12.5 metres (41 ft), while the deepest of these waterbodies reaches depths of 15–16 metres (49–52 ft). The water surface reaches 434 metres (1,424 ft) elevation above sea level, although seasonal variations sometimes cause the lakebodies to dry up. These lakes, some of which have red colours, give Waw an Namus a multicoloured appearance.and additional smaller water bodies, which together form a semicircle around the northern, eastern and southern flanks of the central cone. One of the lakes is north of the scoria cone, the second southeast and south and the third southwest. These lakes cover a total surface of
The lakes are probably groundwater-fed, as evaporation in the area greatly exceeds precipitation, 1,500,000 cubic metres (53,000,000 cu ft) water per year. Freshwater springs nourish the lakes. At least one water body was reported to be fresh in 1951 while the others are warm and saline. Deuterium isotope ratio analysis indicates that the water at Waw an Namus is recent water, certainly more recent than 8,000 years.with the lakes losing about
Waw an Namus is an isolated volcano. 70 kilometres (43 mi) north lie lava flows of basaltic composition and the Haruj volcanic field, of which Waw an Namus is sometimes considered to be a part. These in turn are only two out of several large but little known volcanic fields in the Sahara. A number of theories have been proposed to explain the volcanism in the Sahara, such as the activation of ancient crustal lineaments by the collision between Africa and Europe; in the case of Waw an Namus the magmas originated in the mantle at about 130 kilometres (81 mi) depth.About
The terrain surrounding Waw an Namus is covered by Quaternary sediments.The basement beneath the volcano is crystalline, and is in turn covered by limestone, marl and the Nubian Sandstone.
Alkali basalts have been identified in the scoria,and the occurrence of foidite has been reported. Minerals contained within these rocks include apatite, clinopyroxene, magnetite, nepheline and olivine, and occasionally melilite and sodalite. The rocks contain xenoliths of harzburgite, lherzolite and peridotite. Sulfur occurs within the crater of the scoria cone, as well as white deposits that may be formed by alunite.
Waw an Namus is part of the Sahara desert, one of the world's largest and driest deserts although parts of it were wetter in the past. In some parts of the Sahara it has only rained a few times during a whole century;at Waw an Namus the little precipitation mostly occurs during winter. Wind is the most important weather factor, forming ventifacts and dunes among other structures; at Waw an Namus it mostly blows from the northeast and is sometimes accompanied by dust devils south of the volcano.
The central scoria cone may be only a few thousand years old,possibly even of historical age. The arid climate may mislead as to its actual age, as there is little erosion in the desert. Early geological studies estimated an age of less than 800–1,000 years. Salty muds and rocks erupted by the scoria cone and the crater northwest of the main Waw an Namus caldera must have been emplaced after the last pluvial. The Waw an Namus caldera cuts a Holocene drainage system in the Sahara and there is no evidence of Neolithic artifacts at Waw an Namus, further supporting a recent origin of the volcano.
Radiometric dating failed to yield a reliable age for the rocks;only an imprecise age of 690,000 ± 1,100,000 years ago was obtained. Later potassium-argon dating yielded an age of 200,000 ± 9,000 years before present for a lava bomb associated with the central cone, and the Global Volcanism Program assigns a Pleistocene age to Waw an Namus. Hot springs are active at Waw an Namus and produce sulfurous water.
Acacias, date palms, 4 metres (13 ft) high; smaller reeds and tamarisks grow around the saline lake as well.doum palms, and tamarisks (including Tamarix tetragyna ) grow within the caldera, as well as swamp vegetation to varying degrees. Part of the largest lake is covered with reeds (including Phragmites australis ) up to
Animal life includes aquatic birds, flies and mosquitoes.The oasis has a rich bird life; among the birds are the ducks Anas clypeata (northern shoveler), Anas crecca (Eurasian teal), Anas strepera (gadwall), as well as Acrocephalus scirpaceus (Eurasian reed warbler), Anthus cervinus (red-throated pipit), Anthus pratensis (meadow pipit), Bubulcus ibis (western cattle egret), Corvus ruficollis (brown-necked raven), Falco biarmicus (lanner falcon), Fulica atra (Eurasian coot), Gallinula chloropus (common moorhen), Luscinia svecica (bluethroat), Motacilla alba (white wagtail), Oenanthe deserti (desert wheatear), Passer simplex (desert sparrow), Phoenicurus ochruros (black redstart), Phylloscopus collybita (common chiffchaff), Podyceps nigricollis (black-necked grebe), Rallus aquaticus (water rail), Saxicola rubicola (European stonechat) and Tachybaptus ruficollis (little grebe). Some migratory birds likely use Waw an Namus as an overwintering place. Among microbiota, cyanophyceae, diatoms and green algae are found in the lake waters.
Emi Koussi is a high pyroclastic shield volcano that lies at the southeast end of the Tibesti Mountains in the central Sahara, in the northern Borkou Region of northern Chad. The highest mountain of the Sahara, the volcano is one of several in the Tibesti range, and reaches an elevation of 3,415 metres (11,204 ft), rising 3 km (1.9 mi) above the surrounding sandstone plains. The volcano is 60–70 kilometres (37–43 mi) wide and has a volume of 2,500 cubic kilometres (600 cu mi).
Antofagasta de la Sierra is a volcanic field in Argentina. The main type of volcanic edifice in the area are scoria cones, it is formed by the La Laguna, Jote and Alumbrera volcanoes. The first and last of these form a sub-group which is better researched. Various dating methods have yielded ages from several million to several hundred thousand years ago, but some vents appear to be of Holocene age.
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Ampato is a dormant 6,288-metre (20,630 ft) stratovolcano in the Andes of southern Peru. It lies about 70–75 kilometres (43–47 mi) northwest of Arequipa and is part of a north-south chain that includes the volcanoes Hualca Hualca and Sabancaya, the last of which has been active in historical time.
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Nemo Peak is a stratovolcano located at the northern end of Onekotan Island, Kuril Islands, Russia. It is truncated by two nested calderas, with the cone of Nemo Peak itself rising in the southwest end of the youngest caldera and a crater lake partially filling the northeast part, named Ozero Chernoye.
Quetrupillán is a stratovolcano located in the La Araucanía Region of Chile. It is situated between Villarrica and Lanín volcanoes, within Villarrica National Park. Geologically, Quetrupillán is located in a tectonic basement block between the main traces of Liquiñe-Ofqui Fault and Reigolil-Pirihueico Fault.
Haruj is a large volcanic field spread across 45,000 km2 (17,000 sq mi) in central Libya. It is one of several volcanic fields in Libya along with Tibesti, and its origin has been attributed to the effects of geologic lineaments in the crust.
Sollipulli is an ice-filled volcanic caldera and volcanic complex, which lies southeast of the small town of Melipeuco in the La Araucanía Region, Chile. It is part of the Southern Volcanic Zone of the Andes, one of the four volcanic belts in the Andes chain.
The Barrier Volcano is an active shield volcano located in the north of Kenya. It is last known to have erupted in 1921.
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Ciomadul is a volcano in Romania, and is known as Csomád in Hungarian. It is in the Carpathians, close to the towns of Băile Tușnad and Bixad. It is part of a volcanic chain known as the Călimani (Kelemen) – Gurghiu (Görgényi) – Harghita (Hargita) chain and lies at its southeastern end. Ciomadul consists of several lava domes with two embedded explosion craters known as Mohos and St. Ana, the latter of which contains a crater lake, Lake Sfânta Ana. The dominant volcanic rock at Ciomadul is potassium-rich dacite.
Longgang is a volcanic field in Jilin Province, China. It is also known as Chingyu, Longwan Group or Lung-wan Group. This volcanic field contains over 164 individual centres in the form of crater lakes, maars and volcanic cones and covers a surface area of 1,700 square kilometres (660 sq mi). The field is forested and mostly undisturbed by human activities.
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