Libyan desert glass or Great Sand Sea glass is an impactite, made mostly of lechatelierite, [1] found in areas in the eastern Sahara, in the deserts of eastern Libya and western Egypt. Fragments of desert glass can be found over areas of tens of square kilometers.
The origin of desert glass is uncertain. Meteoritic origins have long been considered possible, and recent research links the glass to impact features, such as zircon breakdown, vaporized quartz and meteoritic metals, and to an impact crater. [2] [3] [4] [5] [6] [7] [8] Some geologists [9] associate the glass with radiative melting from meteoric large aerial bursts, making it analogous to trinitite created from sand exposed to the thermal radiation of a nuclear explosion. Libyan Desert glass has been dated as having formed about 29 million years ago. [10] Like obsidian, it was knapped and used to make tools during the Pleistocene. [11]
For decades, ideas about how the glass formed included melting during meteorite impact, or melting caused by an airburst from an asteroid high in Earth's atmosphere. In May 2019, lybian desert glass samples have been examined by Aaron Cavosie of Curtin University [12] via the electron backscatter diffraction aka EBSD technique, the results were published in the Journal of Geology : the glass is nearly pure silica which requires temperatures above 1,600 °C to form – hotter than any igneous rock on Earth, however, few mineral relics survived from whatever caused the melting, including a form of quartz called cristobalite (a rarely occurring high-temperature mineral) and grains of the mineral zircon derived from reidite, although most have reacted to form a higher-temperature mineral called zirconia when the melt reached over 1,700°C. The presence of still remaining zircon grains transformed from reidite (circa 10%), their orientation and shape revealed to be typical -only- of a meteoritic impact, moreover airbursts never yield this exact type of mineral transformation according to geological records. [10] [13]
Zircon is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is ZrSiO4. An empirical formula showing some of the range of substitution in zircon is (Zr1–y, REEy)(SiO4)1–x(OH)4x–y. Zircon precipitates from silicate melts and has relatively high concentrations of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green.
An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, as the impacting body is usually traveling at several kilometres a second, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale.
Tektites are gravel-sized bodies composed of black, green, brown or grey natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz Eduard Suess (1867–1941), son of Eduard Suess. They generally range in size from millimetres to centimetres. Millimetre-scale tektites are known as microtektites.
Roter Kamm is a meteorite crater, located in the Sperrgebiet, within the Namibian section of the Namib Desert, approximately 80 kilometres (50 mi) north of Oranjemund and 12 kilometres (7.5 mi) southwest of Aurus Mountain in the ǁKaras Region. The crater is 2.5 kilometres (1.6 mi) in diameter and is 130 metres (430 ft) deep. The age is estimated at 4.81 ± 0.5 Ma, placing it in the Pliocene. The crater is exposed at the surface, but its original floor is covered by sand deposits at least 100 metres (330 ft) thick.
Woodleigh is a large meteorite impact structure (astrobleme) in Western Australia, centred on Woodleigh Station east of Shark Bay, Gascoyne region. A team of four scientists at the Geological Survey of Western Australia and the Australian National University, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of Earth and Planetary Science Letters.
A micrometeorite is a micrometeoroid that has survived entry through the Earth's atmosphere. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. The IAU officially defines meteoroids as 30 micrometers to 1 meter; micrometeorites are the small end of the range (~submillimeter). They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs).
Lechatelierite is silica glass, amorphous SiO2, non-crystalline mineraloid. It is named for Henry Louis Le Chatelier.
Edeowie glass is a natural glass, or lechatelierite, found in the Australian state of South Australia. It is slag-like, opaque material found as vesicular free forms or sheet-like/ropy masses. It is located throughout a semi-continuous swath in baked pod-like clay-bearing sediment in an area of about 55 kilometres (34 mi) long by 10 kilometres (6.2 mi) along the western side of the Flinders Ranges near Parachilna and east of Lake Torrens. The region in which this glass is found is mostly restricted to concentrations correlated to the ancient shoreline terrace sequence at the locality. It is typically black in appearance, but can occur as variegated grey-green with various streak-like impurities. Pale grey and red-brownish surfaces can be caused by chemical weathering and devitrification.
Kebira Crater is the name given to a circular topographic feature that was identified in 2007 by Farouk El-Baz and Eman Ghoneim using satellite imagery, Radarsat-1, and Shuttle Radar Topography Mission (SRTM) data in the Sahara desert. This feature straddles the border between Egypt and Libya. The name of this feature is derived from the Arabic word for "large", and also from its location near the Gilf Kebir region in southwest Egypt. Based solely on their interpretations of the remote sensing data, they argue that this feature is an exceptionally large, double-ringed, extraterrestrial impact crater. They suggest that the crater's original appearance has been obscured by wind and water erosion over time. Finally, they speculated that this feature might be the source of the yellow-green silica glass fragments, known as "Libyan desert glass", that can be found across part of Egypt's Libyan Desert. They neither conducted any fieldwork at this feature nor studied any samples collected from it. However, the Kebira Crater is currently not listed in the Earth Impact Database. Field trips to investigate the feature have found no supporting evidence. The "central uplift" clearly retains the horizontal bedding of the surrounding sandstone tableland, providing clear evidence against a possible impact origin.
Dhala crater is an impact structure formed by an asteroid impact. It is situated near Bhonti village in Pichhore block of Shivpuri district of Madhya Pradesh state in India. It is the largest impact structure in India, and between the Mediterranean and Southeast Asia. The diameter of the structure is estimated at 3 kilometres (1.9 mi), while other sources estimate its diameter to be 11 km diameter. It is the second such structure found in India, after Lonar lake.
Lodranites are a small group of primitive achondrite meteorites that consists of meteoric iron and silicate minerals. Olivine and pyroxene make up most of the silicate minerals. Like all primitive achondrites lodranites share similarities with chondrites and achondrites.
The Itqiy meteorite is an enstatite-rich stony-iron meteorite. It is classified as an enstatite chondrite of the EH group that was nearly melted and is therefore very unusual for that group. Other classifications have been proposed and are an ongoing scientific debate.
This is a glossary of terms used in meteoritics, the science of meteorites.
Reidite is a rare polymorph of ZrSiO4 created when zircon experiences high pressure and temperature. Reidite is denser than zircon and has the same crystal structure as scheelite. All natural occurrences of reidite are associated with meteorite impact events.
Hypatia is a small stone found in Egypt in 1996. It has been claimed to be both a meteorite and kimberlite debris. It has also been claimed to be the first known specimen of a comet nucleus on Earth, although defying physically-accepted models for hypervelocity processing of organic material. As of November 2023, Hypatia has not been officially classified as a meteorite in the Meteoritical Bulletin, which is tasked with recording all scientifically proven meteorites.
The Maniitsoq structure was a proposed 3 billion-year-old impact structure located in the Akia terrane of the North Atlantic Craton, centred about 55 km (34 mi) south-east of the town of Maniitsoq, Greenland, at 65°15′N51°50′W. However, the Maniitsoq structure has not been widely recognised as an impact structure, and the proposal was criticised for not meeting established criteria for recognising impact craters. Furthermore, subsequent studies in the region have demonstrated that there is no evidence for an impact structure, and in fact a number of observations directly contradict the earlier impact structure proposals. The Maniitsoq structure is not recognised as an impact structure by the Earth Impact Database.
Hadean zircon is the oldest-surviving crustal material from the Earth's earliest geological time period, the Hadean eon, about 4 billion years ago. Zircon is a mineral that is commonly used for radiometric dating because it is highly resistant to chemical changes and appears in the form of small crystals or grains in most igneous and metamorphic host rocks.
Monturaqui is an impact crater in Chile. It lies south of the Salar de Atacama and was formed 663,000 ± 90,000 years ago by the impact of an IAB meteorite. It is 350 m × 370 m wide and 34 m (112 ft) deep and contains a salt pan. Only a few remnants of the meteorite that formed the crater have been collected, with most of the rocks being of local origin. The crater was discovered in 1962 and identified as an impact crater in 1966.
