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. Like obsidian, it was knapped and used to make tools during the Pleistocene. [2]
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. [3] [4] [5] [6] [7] [8] [9] Some geologists [10] 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. [11]
Analysis of samples with the electron backscatter diffraction (EBSD) technique revealed zircon crystal structures that form only when reidite melts at very high temperatures and is then converted to zircon. [11] Reidite has been found only at meteorite impact sites, where it was formed at the very high pressures of impact. Airbursts never yield this type of mineral transformation. [12]
A meteorite is a rock that originated in outer space and has fallen to the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star; astronomers call the brightest examples "bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater.
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.
Lappajärvi is a lake in Finland, in the municipalities of Lappajärvi, Alajärvi and Vimpeli. It is formed in a 23 km (14 mi) wide, partly eroded meteorite impact crater. The lake is part of Ähtävänjoki basin together with Lake Evijärvi that is located downstream (north) of it.
The Popigai impact structure is the eroded remnant of an impact crater in northern Siberia, Russia. It is tied with the Manicouagan structure as the fourth largest verified impact structure on Earth. A large bolide impact created the 100-kilometre (62 mi) diameter crater approximately 35 million years ago during the late Eocene epoch. It might be linked to the Eocene–Oligocene extinction event.
Rochechouart impact structure or Rochechouart astrobleme is an impact structure in France. Erosion has over the millions of years mostly destroyed its impact crater, the initial surface expression of the asteroid impact leaving highly deformed bedrock and fragments of the crater's floor as evidence of it.
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.
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.
Nonmagmatic meteorite is a deprecated term formerly used in meteoritics to describe iron meteorites that were originally thought to have not formed by igneous processes, to differentiate them from the magmatic meteorites, produced by the crystallization of a metal melt. The concept behind this was developed in the 1970s, but it was quickly realized that igneous processes actually play a vital role in the formation of the so-called "nonmagmatic" meteorites. Today, the terms are still sometimes used, but usage is discouraged because of the ambiguous meanings of the terms magmatic and nonmagmatic. The meteorites that were described to be nonmagmatic are now understood to be the product of partial melting and impact events and are grouped with the primitive achondrites and the achondrites.
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 is 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. Its origin has been debated since it was first proposed as an impact structure in 2012. The Maniitsoq structure is not recognised as an impact structure by the Earth Impact Database.
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.
