Тектиты: Стекловидные образования, образовавшиеся при метеоритных ударах.

Gravel sized glass beads formed from meteorite impacts
impact rocks

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. Tektites are characterized by:
a fairly homogeneous composition
an extremely low content of water and other volatiles
an abundance of lechatelierite
a general lack of microscopic crystals known as microlites
not having a chemical relationship to the local bedrock or local sediments
their distribution within geographically extensive strewn fields

Although tektites are superficially similar to some terrestrial volcanic glasses (obsidians), they have unusual distinctive physical characteristics that distinguish them from such glasses. First, they are completely glassy and lack any microlites or phenocrysts, unlike terrestrial volcanic glasses. Second, although high in silica (>65 wt%), the bulk chemical and isotopic composition of tektites is closer to those of shales and similar sedimentary rocks and quite different from the bulk chemical and isotopic composition of terrestrial volcanic glasses. Third, tektites contain virtually no water (<0.02 wt%), unlike terrestrial volcanic glasses. Fourth, the flow banding within tektites often contains particles and bands of lechatelierite, which are not found in terrestrial volcanic glasses. Finally, a few tektites contain partly melted inclusions of shocked and unshocked mineral grains, i. e. quartz, apatite, and zircon, as well as coesite.

On the basis of morphology and physical characteristics, tektites have traditionally been divided into four groups. Those found on land have traditionally been subdivided into three groups: (1) splash form (normal) tektites, (2) aerodynamically shaped tektites, and (3) Muong Nong type (layered) tektites. Splash form and aerodynamically shaped tektites are only differentiated on the basis of their appearance and some of their physical characteristics. Splash form tektites are centimeter sized tektites that are shaped like spheres, ellipsoids, teardrops, dumbbells, and other forms characteristic of isolated molten bodies. They are regarded as having formed from the solidification of rotating liquids, and not atmospheric ablation. Aerodynamically shaped tektites, which are mainly part of the Australasian strewn field, are splash form tektites (buttons) which display a secondary ring or flange. The secondary ring or flange is argued as having been produced during the high speed re entry and ablation of a solidified splash form tektite into the atmosphere. Muong Nong tektites are typically larger, greater than 10 cm in size and 24 kg in weight, irregular, and layered tektites. They have a chunky, blocky appearance, exhibit a layered structure with abundant vesicles, and contain mineral inclusions, such as zircon, baddeleyite, chromite, rutile, corundum, cristobalite, and coesite.

The ages of tektites from the four strewnfields have been determined using radiometric dating methods. The age of moldavites, a type of tektite found in the Czech Republic, was determined to be 14 million years, which agrees well with the age determined for the Nördlinger Ries crater (a few hundred kilometers away in Germany) by radiometric dating of Suevite (an impact breccia found at the crater). Similar agreements exist between tektites from the North American strewnfield and the Chesapeake Bay impact crater and between tektites from the Ivory Coast strewnfield and the Lake Bosumtwi Crater. Ages of tektites have usually been determined by either the K Ar method, fission track dating, the Ar Ar technique, or combination of these techniques.

The overwhelming consensus of Earth and planetary scientists is that tektites consist of terrestrial debris that was ejected during the formation of an impact crater. During the extreme conditions created by a hypervelocity meteorite impact, near surface terrestrial sediments and rocks were either melted, vaporized, or some combination of these, and ejected from an impact crater. After ejection from the impact crater, the material formed millimeter to centimeter sized bodies of molten material, which as they re entered the atmosphere, rapidly cooled to form tektites that fell to Earth to create a layer of distal ejecta hundreds or thousands of kilometers away from the impact site. The terrestrial source for tektites is supported by well documented evidence. The chemical and isotopic composition of tektites indicates that they are derived from the melting of silica rich crustal and sedimentary rocks, which are not found on the Moon. In addition, some tektites contain relict mineral inclusions (quartz, zircon, rutile, chromite, and monazite) that are characteristic of terrestrial sediments and crustal and sedimentary source rocks. Also, three of the four tektite strewnfields have been linked by their age and chemical and isotopic composition to known impact craters. A number of different geochemical studies of tektites from the Australasian strewnfield concluded that these tektites consist of melted Jurassic sediments, or sedimentary rocks that were weathered and deposited about 167 Mya. Their geochemistry suggests that the source of Australasian tektites is a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Mya, more or less. This effectively refutes multiple impact hypotheses. Verbeek's proposal of an extraterrestrial origin for tektites was soon seconded by the Austrian geologist Franz E. Suess. Subsequently, it was argued that tektites consist of material that was ejected from the Moon by major hydrogen driven lunar volcanic eruptions and then drifted through space to later fall to Earth as tektites. The major proponents of the lunar origin of tektites include NASA scientist John A. O'Keefe, NASA aerodynamicist Dean R. Chapman, meteorite and tektite collector Darryl Futrell, and long time tektite researcher Hal Povenmire. From the 1950s to the 1990s, O'Keefe argued for the lunar origin of tektites based upon their chemical, i. e. rare earth, isotopic, and bulk, composition and physical properties. O'Keefe, Povenmire, and Futrell claimed on the basis of behavior of glass melts that the homogenization, which is called "fining", of silica melts that characterize tektites could not be explained by the terrestrial impact theory. They also argued that the terrestrial impact theory could not explain the vesicles and extremely low water and other volatile content of tektites. At one time, theories advocating the lunar origin of tektites enjoyed considerable support as part of a spirited controversy about the origin of tektites that occurred during the 1960s. Starting with the publication of research concerning lunar samples returned from the Moon, the consensus of Earth and planetary scientists shifted in favor of theories advocating a terrestrial impact versus lunar volcanic origin. For example, one problem with the lunar origin theory is that the arguments for it that are based upon the behavior of glass melts use data from pressures and temperatures that are vastly uncharacteristic of and unrelated to the extreme conditions of hypervelocity impacts. In addition, various studies have shown that hypervelocity impacts are likely quite capable of producing low volatile melts with extremely low water content.