Wabar craters
Encyclopedia
The Wabar craters are impact crater
s brought to the attention of Western scholars by an explorer searching for the legendary city of Ubar in Arabia.
known as the "Empty Quarter
", or "Rub' al Khali" in Arabic, is one of the most desolate places on Earth. In 1932, a British explorer, Harry St. John "Abdullah" Philby, father of Soviet spy Kim Philby
, was hunting for a city named "Ubar", that the Qur'an
claimed had been destroyed by God for defying the Prophet Hud
. Philby transliterated the name of the city as "Wabar".
Philby had heard of bedouin legends of an area called Al Hadida ('place of iron' in Arabic) with ruins of ancient habitations, and also an area where a piece of iron the size of a camel had been found, and so organized an expedition to visit the site. After a month's journey through wastes so harsh that even some of the camels died, on 2 February 1932 Philby arrived at a patch of ground about a half a square kilometer in size, littered with chunks of white sandstone
, black glass
, and chunks of iron meteorite
. Philby identified two large circular depressions partially filled with sand, and three other features that he identified as possible 'submerged craters'. He also mapped the area where the large iron block was reputed to have been found. Philby thought the area a volcano, and it was only after bringing back samples to the UK that the site was identified as that of a meteorite impact by Dr Leonard James Spencer
of the British Museum
.
Amongst the samples of iron, cindery material and silica glass that Philby brought back from the site was a 25lb chunk of iron. Analysis showed it to be about 90% iron and 5% nickel, with the rest consisting of various elements, including copper, cobalt, and 0.0006% (6 ppm)—an unusually high concentration—of iridium
. This so-called siderophile
element implied that the "Wabar" site was a meteorite
impact area.
geologists T. F. Harriss and Walton Hoag Jr. also investigated the site, but, like Philby, were unable to locate the large block of iron.
journalist Thomas J. Abercrombie visited the site and found the large meteorite: "rumor has become a reality; the biggest iron meteorite ever found in Arabia lay at our feet... shaped roughly like a saucer, it measured about four feet in diameter and two feet thick at center. A little quick geometry puts its weight at almost two and a half tons."
Later in October 1966, a group headed by Aramco employee James Mandaville visited the site with heavy lifting equipment. They found two large uncovered meteorites. The largest, weighing 2,045 kilograms, had a pitted but roughly level top surface about a meter (3.5 feet) in diameter with one end formed into a cone shape when the meteorite penetrated the atmosphere like a bullet — was imbedded in sand, which had drifted over the top. It was photographed in situ, then overturned by a bulldozer and lifted on board a trailer where it and another, smaller meteorite were taken to Dhahran.
joined all three expeditions, and astronomer and geologist Gene Shoemaker
joined at least one. These expeditions were made with modern offroad vehicles into the Empty Quarter, but even with modern technology, the trips were difficult ones. Not only were conditions harsh, but the Wabar site was tricky to find, as it sits in the midst of an enormous dune field that has no fixed landmarks.
The surface of the area partly consisted of "Insta-Rock" or "impactite
", a bleached-white, coarsely-laminar sandstone-look-alike, and was littered with black glass slag
and pellets. The impactite featured a form of shocked quartz
known as "coesite
", and is thus clearly the product of an impact event. The impact did not penetrate to bedrock
but was confined to local sand, making it particularly valuable as a research site.
The presence of iron fragments at the site also pointed to a meteorite impact, as there are no iron deposits in the region. The iron was in the form of buried fist-sized cracked balls and smooth, sand-blasted fragments found on the surface. The largest fragment was recovered in a 1966 visit to Wabar and weighs 2.2 tonnes. It is known as the "Camel's Hump" and was on display at the King Saud University
in Riyadh
until it became the entry piece for the new National Museum of Saudi Arabia
in Riyadh.
The sand was turned into black glass near the craters, and pellets of the glass are scattered all over the area, decreasing in size with distance from the craters due to wind-sorting. The glass is about 90% local sand and 10% meteoritic iron and nickel.
The layout of the impact area suggests that the body fell at a shallow angle, and was moving at typical meteorite entry speeds of 40,000 to 60,000 km/h. Its total mass was more than 3,500 tonnes. The shallow angle presented the body with more air resistance than it would have encountered at a steeper angle, and it broke up in the air into at least four pieces before impact. The biggest piece struck with an explosion roughly equivalent to the atom bomb that leveled Hiroshima
.
analysis of glass fragments by Storzer suggested the Wabar impact took place thousands of years ago, but the fact that the craters have been filled-in considerably since Philby visited them suggests their origin is much more recent. Thermoluminescence dating
by Prescott et al. (2004) suggest the impact site is no more than 260 years old. Arab reports of a fireball passing over Riyadh
, variously reported as occurring in 1863 or 1891, indicate the impact may have occurred very recently. Fragments scattered from the path of this fireball match samples found at the Wabar site.
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
s brought to the attention of Western scholars by an explorer searching for the legendary city of Ubar in Arabia.
1932 Philby
The vast desert wasteland of southern Saudi ArabiaSaudi Arabia
The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
known as the "Empty Quarter
Empty Quarter
The Rub' al Khali or Empty Quarter is one of the largest sand deserts in the world, encompassing most of the southern third of the Arabian Peninsula, including most of Saudi Arabia and areas of Oman, the United Arab Emirates, and Yemen. The desert covers some The Rub' al Khali or Empty Quarter...
", or "Rub' al Khali" in Arabic, is one of the most desolate places on Earth. In 1932, a British explorer, Harry St. John "Abdullah" Philby, father of Soviet spy Kim Philby
Kim Philby
Harold Adrian Russell "Kim" Philby was a high-ranking member of British intelligence who worked as a spy for and later defected to the Soviet Union...
, was hunting for a city named "Ubar", that the Qur'an
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...
claimed had been destroyed by God for defying the Prophet Hud
Hud (prophet)
Hud is the name of a prophet of ancient Arabia, who is mentioned in the Qur'an. The eleventh chapter of the Qur'an, Hud, is named after him, though the narrative of Hud comprises only a small portion of the chapter.-Historical context:...
. Philby transliterated the name of the city as "Wabar".
Philby had heard of bedouin legends of an area called Al Hadida ('place of iron' in Arabic) with ruins of ancient habitations, and also an area where a piece of iron the size of a camel had been found, and so organized an expedition to visit the site. After a month's journey through wastes so harsh that even some of the camels died, on 2 February 1932 Philby arrived at a patch of ground about a half a square kilometer in size, littered with chunks of white sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
, black glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
, and chunks of iron meteorite
Iron meteorite
Iron meteorites are meteorites that consist overwhelmingly of nickel-iron alloys. The metal taken from these meteorites is known as meteoric iron and was one of the earliest sources of usable iron available to humans.-Occurrence:...
. Philby identified two large circular depressions partially filled with sand, and three other features that he identified as possible 'submerged craters'. He also mapped the area where the large iron block was reputed to have been found. Philby thought the area a volcano, and it was only after bringing back samples to the UK that the site was identified as that of a meteorite impact by Dr Leonard James Spencer
Leonard James Spencer
Leonard James Spencer CBE FRS was a British geologist. He was an Honorary member of the Royal Geological Society of Cornwall, and also a recipient of its Bolitho Medal. He was president of the Mineralogical Society of Great Britain and Ireland from 1936 to 1939...
of the British Museum
British Museum
The British Museum is a museum of human history and culture in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from its...
.
A volcano in the midst of the Rub' al Khali! And below me, as I stood on that hill-top transfixed, lay the twin craters, whose black walls stood up gauntly above the encroaching sand like the battlements and bastions of some great castle. These craters were respectively about 100 and 50 yards in diameter, sunken in the middle but half choked with sand, while inside and outside their walls lay what I took to be lava in great circles where it seemed to have flowed out from the fiery furnace. Further examination revealed the fact that there were three similar craters close by, though these were surmounted by hills of sand and recognizable only by reason of the fringe of blackened slag round their edges.
Amongst the samples of iron, cindery material and silica glass that Philby brought back from the site was a 25lb chunk of iron. Analysis showed it to be about 90% iron and 5% nickel, with the rest consisting of various elements, including copper, cobalt, and 0.0006% (6 ppm)—an unusually high concentration—of iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
. This so-called siderophile
Siderophile
Siderophile means "iron-loving". This can refer to:* Siderophilic bacteria, bacteria that require or are facilitated by free iron* Siderophile elements, chemical elements such as iridium or gold that tend to bond with metallic iron, as described by the Goldschmidt classification* Siderophilia,...
element implied that the "Wabar" site was a meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
impact area.
1937 Aramco
In 1937, AramcoSaudi Aramco
Saudi Aramco , officially the Saudi Arabian Oil Company, is the national oil company of Saudi Arabia.Saudi Aramco is the world's largest and most valuable privately-held company, with estimates of its value in 2011 to be $7 trillion USD.Saudi Aramco has both the largest proven crude oil reserves,...
geologists T. F. Harriss and Walton Hoag Jr. also investigated the site, but, like Philby, were unable to locate the large block of iron.
1966 National Geographic and Aramco
In 1966 reports came that the sands had shifted and the large iron block was again visible. National Geographic MagazineNational Geographic Magazine
National Geographic, formerly the National Geographic Magazine, is the official journal of the National Geographic Society. It published its first issue in 1888, just nine months after the Society itself was founded...
journalist Thomas J. Abercrombie visited the site and found the large meteorite: "rumor has become a reality; the biggest iron meteorite ever found in Arabia lay at our feet... shaped roughly like a saucer, it measured about four feet in diameter and two feet thick at center. A little quick geometry puts its weight at almost two and a half tons."
Later in October 1966, a group headed by Aramco employee James Mandaville visited the site with heavy lifting equipment. They found two large uncovered meteorites. The largest, weighing 2,045 kilograms, had a pitted but roughly level top surface about a meter (3.5 feet) in diameter with one end formed into a cone shape when the meteorite penetrated the atmosphere like a bullet — was imbedded in sand, which had drifted over the top. It was photographed in situ, then overturned by a bulldozer and lifted on board a trailer where it and another, smaller meteorite were taken to Dhahran.
1982 Aramco
Mandaville visited the site twice after his 1966 visit. On his last visit, in 1982, he noted that the desert winds and resultant movement of the dune system were covering the site: "instead of two thirds of the crater rim (visible as before [ie in 1966, 16 years earlier]), less than a quarter of it showed."1994-5 Zahid
In 1994 and 1995 a total of three expeditions were undertaken, sponsored by Zahid Tractor Corporation. A U.S. Geological Survey scientist, Jeffrey C. WynnJeffrey C. Wynn
Dr Jeffrey C. Wynn , is a research geophysicist with the US GeologicalSurvey. He is currently based in the Cascades Volcano Observatory inVancouver, WA, one of the five USGS volcano observatories in the United States.LEADERSHIP...
joined all three expeditions, and astronomer and geologist Gene Shoemaker
Eugene Merle Shoemaker
Eugene Merle Shoemaker , American geologist, was one of the founders of the fields of planetary science....
joined at least one. These expeditions were made with modern offroad vehicles into the Empty Quarter, but even with modern technology, the trips were difficult ones. Not only were conditions harsh, but the Wabar site was tricky to find, as it sits in the midst of an enormous dune field that has no fixed landmarks.
The site
The Wabar site covers about 500 by 1,000 meters, and the most recent mapping shows three prominent, roughly circular craters. Five were reported by Philby in 1932, the largest of which measure 116 and 64 meters wide. Another was described by the 2nd Zahid expedition and is 11 meters wide: this may be one of the other three originally described by Philby. They are all underlain by a hemispherical rim of "insta-Rock," so called because it was created from local sand by the impact shock wave, and all three are nearly full of sand.The surface of the area partly consisted of "Insta-Rock" or "impactite
Impactite
Impactite is an informal term describing a rock created or modified by the impact of a meteorite. The term encompasses shock-metamorphosed target rocks, melts and mixtures of the two, as well as sedimentary rocks with significant impact-derived components .-Some localities:*Nördlinger Ries...
", a bleached-white, coarsely-laminar sandstone-look-alike, and was littered with black glass slag
Slag
Slag is a partially vitreous by-product of smelting ore to separate the metal fraction from the unwanted fraction. It can usually be considered to be a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and metal atoms in the elemental form...
and pellets. The impactite featured a form of shocked quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
known as "coesite
Coesite
Coesite[p] is a form of silicon dioxide SiO2 that is formed when very high pressure , and moderately high temperature , are applied to quartz. Coesite was first synthesized by Loring Coes, Jr., a chemist at the Norton Company, in 1953. In 1960, coesite was found by Edward C. T...
", and is thus clearly the product of an impact event. The impact did not penetrate to bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
but was confined to local sand, making it particularly valuable as a research site.
The presence of iron fragments at the site also pointed to a meteorite impact, as there are no iron deposits in the region. The iron was in the form of buried fist-sized cracked balls and smooth, sand-blasted fragments found on the surface. The largest fragment was recovered in a 1966 visit to Wabar and weighs 2.2 tonnes. It is known as the "Camel's Hump" and was on display at the King Saud University
King Saud University
King Saud University is a public university located in Riyadh, Saudi Arabia. It was founded in 1957 by King Saud bin Abdul Aziz as Riyadh University, as the first university in the kingdom not dedicated to religious subjects. The university was created to meet the shortage of skilled workers in...
in Riyadh
Riyadh
Riyadh is the capital and largest city of Saudi Arabia. It is also the capital of Riyadh Province, and belongs to the historical regions of Najd and Al-Yamama. It is situated in the center of the Arabian Peninsula on a large plateau, and is home to 5,254,560 people, and the urban center of a...
until it became the entry piece for the new National Museum of Saudi Arabia
National Museum of Saudi Arabia
The National Museum of Saudi Arabia is a major national museum in Saudi Arabia. Established in 1999, it is part of the King Abdul Aziz Historical Centre in Riyadh.- The building :...
in Riyadh.
The sand was turned into black glass near the craters, and pellets of the glass are scattered all over the area, decreasing in size with distance from the craters due to wind-sorting. The glass is about 90% local sand and 10% meteoritic iron and nickel.
The layout of the impact area suggests that the body fell at a shallow angle, and was moving at typical meteorite entry speeds of 40,000 to 60,000 km/h. Its total mass was more than 3,500 tonnes. The shallow angle presented the body with more air resistance than it would have encountered at a steeper angle, and it broke up in the air into at least four pieces before impact. The biggest piece struck with an explosion roughly equivalent to the atom bomb that leveled Hiroshima
Hiroshima
is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshu, the largest island of Japan. It became best known as the first city in history to be destroyed by a nuclear weapon when the United States Army Air Forces dropped an atomic bomb on it at 8:15 A.M...
.
Dating the impact event
Fission-trackFission track dating
Fission track dating is a radiometric dating technique based on analyses of the damage trails, or tracks, left by fission fragments in certain uranium-bearing minerals and glasses...
analysis of glass fragments by Storzer suggested the Wabar impact took place thousands of years ago, but the fact that the craters have been filled-in considerably since Philby visited them suggests their origin is much more recent. Thermoluminescence dating
Thermoluminescence dating
Thermoluminescence dating is the determination, by means of measuring the accumulated radiation dose, of the time elapsed since material containing crystalline minerals was either heated or exposed to sunlight...
by Prescott et al. (2004) suggest the impact site is no more than 260 years old. Arab reports of a fireball passing over Riyadh
Riyadh
Riyadh is the capital and largest city of Saudi Arabia. It is also the capital of Riyadh Province, and belongs to the historical regions of Najd and Al-Yamama. It is situated in the center of the Arabian Peninsula on a large plateau, and is home to 5,254,560 people, and the urban center of a...
, variously reported as occurring in 1863 or 1891, indicate the impact may have occurred very recently. Fragments scattered from the path of this fireball match samples found at the Wabar site.
External links
- US Geological Survey report. Jeff Wynn and Gene Shoemaker
- The large meteorite fragment (The Camel's Hump') before its removal from the site. Photograph taken by James Mandaville, 1966
- One of the large Wabar craters. Photograph taken by James Mandaville, 1966
- Description of a piece from the meteor.
- Wynn expeditions
- Photographs
- Information and aerial photograph of one of the craters. Scroll 1/4 of way down page