Howardites
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#Impact processes

Craters, shock waves and breccias: what collisions do to rock, recorded in meteorites and on Earth.

Collisions shape every rocky body in the Solar System. When an asteroid strikes, a shock wave passes through the rock in a fraction of a second, creating pressures and temperatures far beyond anything found in Earth's crust.

Meteorites record these events. They can contain shock veins of melted rock, high-pressure minerals such as ringwoodite, feldspar turned to glass, and breccias made of broken fragments welded back together. Scientists grade the damage on a scale of shock stages.

On Earth, the same clues, together with shatter cones and shocked quartz, reveal ancient impact craters even where erosion has worn the crater itself away.

Part of Meteorites across the sciences.

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Lessons (1)

  • Shock and weathering gradesClassification codes often end with an S and a W number, as in L6 S4 W1. These record what impacts did to the rock in space, and what Earth

Courses (5)

  • Gravitational fields and escapeHow does a rock leave Mars, the Moon or the asteroid Vesta? Newton's law of gravitation and the idea of gravitational potential give the
  • Shock, craters and deflecting an asteroidHypervelocity impacts generate shock pressures that transform minerals. This final lesson connects shock metamorphism, crater evidence and t
  • Impacts in Earth's historyImpacts have shaped Earth from its formation to the present. This lesson looks at craters, the end of the dinosaurs, modern airbursts and ho
  • The kinetic energy of space rocksBecause they move so fast, even small meteoroids carry huge amounts of energy. This lesson uses the kinetic energy equation to explain fireb
  • Investigating cratersImpact craters are found on every rocky world. In this lesson you will plan a fair investigation into crater size and connect it to the ener

Famous meteorites (7)

  • AbeeA 107-kilogram enstatite chondrite that fell on a Canadian wheat field in 1952 – a rare sample of rock formed with almost no oxygen.
  • Allan Hills 81005A golf-ball-sized rock found in Antarctica in 1982 – the first meteorite recognised as coming from the Moon.
  • ChelyabinskThe 2013 airburst over Russia that shattered thousands of windows and reminded the world that asteroid impacts still happen.
  • KaidunA small stone that fell on a military base in Yemen in 1980 and turned out to be a jigsaw of many different worlds.
  • NWA 7034Nicknamed Black Beauty, this dark Martian breccia contains the oldest pieces of Mars yet found.
  • ShergottyThe 1865 fall in India that gave its name to the most common family of Martian meteorites.
  • ZagamiA piece of Martian lava that landed close to a Nigerian farmer in 1962 – the largest single Martian stone ever seen to fall.

Meteorite types (10)

  • ChondritesPrimitive stones that never melted, made of the first solids of the Solar System. The most common meteorites of all.
  • EH chondritesHigh-iron enstatite chondrites. EH chondrites have more metal and smaller chondrules than EL chondrites, and contain niningerite, a magnesiu
  • EucritesVolcanic basalt from the crust of Vesta. Eucrites are basalts and gabbros from Vesta's crust, made mainly of pigeonite (a calcium-poor p
  • Lunar basalts and gabbrosDark volcanic rock from the lunar maria, the Moon's great lava plains. Lunar basalts are pieces of the dark lava plains, the maria, that
  • Feldspathic lunar meteoritesPale breccias from the ancient lunar highlands, the most common kind of Moon rock to reach Earth.
  • Lunar meteoritesRocks from the Moon, found mainly in deserts and Antarctica. Lunar meteorites are pieces of the Moon blasted off by impacts.
  • Mingled lunar brecciasBreccias that mix highland and mare rock, from the borders between the two. Mingled breccias contain both pale highland material and dark ma
  • ALH 84001 and other Martian rocksThe ancient Martian rock once claimed to hold fossils, and 'Black Beauty'. Allan Hills 84001, found in Antarctica in December 1984,
  • R chondrites (rumurutiites)Highly oxidised chondrites with almost no metal. R chondrites are named after Rumuruti in Kenya, the only one seen to fall (1934).
  • ShergottitesThe most common Martian meteorites: young basaltic and olivine-rich rocks. Shergottites, named after Shergotty in India (fell 1865), make up

Space missions (2)

  • Apollo 14Rocks thrown out by the giant impact that made the Imbrium basin. Apollo 14 landed on 5 February 1971 in the Fra Mauro hills, the target tha
  • Apollo 16The only Apollo landing in the central highlands, and a surprise about how they formed.

Meteorite minerals (19)

  • AhrensiteThe iron-rich, spinel-structured form of olivine, the iron partner of ringwoodite. Ahrensite has the chemistry of fayalite and the structure
  • AkimotoiteA high-pressure form of pyroxene with the ilmenite structure, formed in shocked meteorites.
  • CoesiteA high-pressure form of silica that marks impacts on Earth and occurs in some shocked meteorites. Coesite is silica packed more densely than
  • DonwilhelmsiteA dense calcium aluminium silicate in lunar meteorites, made from shock-melted Moon crust.
  • ElgoresyiteA dense magnesium–iron silicate with an unusual ratio of metal to silicon, found in a shock vein of the Suizhou chondrite.
  • JadeiteThe sodium pyroxene of jade, which also forms in the shock veins of meteorites. Jadeite is a pyroxene of sodium and aluminium.
  • LinguniteThe dense hollandite-structured form of feldspar, found in shock veins of chondrites.
  • MajoriteA garnet made from pyroxene at high pressure, in which silicon takes an unusual place.
  • MaskelynitePlagioclase feldspar turned to glass by shock, without melting, while keeping its crystal shape.
  • PoirieriteA rare form of olivine composition, halfway in structure between olivine and its high-pressure forms, found in shock veins of chondrites.
  • RingwooditeThe dense, spinel-structured form of olivine, made by shock in meteorites and found deep inside Earth.
  • SeifertiteThe densest known natural form of silica, formed by shock in Martian meteorites. Seifertite is silicon dioxide with a structure related to t
  • Silica minerals: tridymite, cristobalite and quartzSilicon dioxide in its different crystal forms, found in eucrites, enstatite chondrites and lunar basalts. Silica is silicon dioxide.
  • StishoviteA very dense form of silica, made by impacts, in which silicon is surrounded by six oxygen atoms.
  • StöffleriteCalcium feldspar in the dense hollandite structure: the high-pressure partner of anorthite.
  • TuiteThe high-pressure form of the meteorite phosphate merrillite, found in shock veins. Tuite is calcium phosphate with a dense structure.
  • WadsleyiteA high-pressure form of olivine, between olivine and ringwoodite, found in shocked meteorites.
  • XieiteA dense, high-pressure form of chromite found in a shocked Chinese chondrite. Xieite has the chemistry of chromite but a denser structure.
  • ZagamiiteA dense calcium aluminium silicate that crystallised from shock melt in Martian meteorites.

Glossary (41)

Questions and answers (12)

Impact craters (52)

  • AcramanAcraman, in the Gawler Ranges of South Australia, is a crater whose story was pieced together from two places about 300 km apart.
  • Amelia CreekAmelia Creek is a deeply eroded impact structure in the Davenport Ranges of the Northern Territory, Australia, south-east of Tennant Creek.
  • BeaverheadBeaverhead is one of the oldest and largest impact structures in North America, estimated to have been about 60 km across when it formed.
  • BoltyshBoltysh is a buried impact crater in central Ukraine, in the Kirovohrad region. You cannot see it at the surface, where it lies beneath fiel
  • CarswellCarswell is an eroded impact structure about 39 km across in the far north of Saskatchewan, Canada, on the western side of the Athabasca Bas
  • CoutureCouture is an impact crater about 8 km across, filled by the round waters of Lac Couture in the Nunavik region of northern Quebec, in Canada
  • CrawfordCrawford is a deeply eroded impact structure about 8.5 km across in South Australia, north-east of Adelaide.
  • Crooked CreekCrooked Creek is an eroded impact structure about 7 km across in Crawford County, in the Ozark region of Missouri, in the United States.
  • DellenDellen is an eroded impact structure about 19 km across in the province of Hälsingland, central Sweden.
  • DhalaDhala is an ancient impact structure about 11 km across near the village of Dhala in Shivpuri district, Madhya Pradesh, central India.
  • FlaxmanFlaxman is a deeply eroded impact structure about 10 km across in South Australia, north-east of Adelaide, a few kilometres from the similar
  • GardnosGardnos, in the valley of Hallingdal in southern Norway, is an ancient impact crater known for its unusual black rocks.
  • GliksonGlikson is an eroded impact structure about 19 km across in the Little Sandy Desert of Western Australia.
  • Glover BluffGlover Bluff is a deeply eroded impact structure in Marquette County, south-central Wisconsin, in the United States.
  • Gosses BluffGosses Bluff rises abruptly from the flat plains of the Northern Territory, about 175 km west of Alice Springs.
  • GowGow is a small impact crater about 4 to 5 km across in northern Saskatchewan, in Canada, filled by the waters of Gow Lake, south of the much
  • GranbyGranby is a buried impact crater about 3 km across in Östergötland, southern Sweden, just east of Lake Vättern.
  • Gweni-FadaGweni-Fada is a crater that was found from space. It lies in the Ennedi region of north-eastern Chad, a remote area of sandstone plateaus, c
  • Île RouleauÎle Rouleau is a small island in Lake Mistassini, the largest natural lake in Quebec, in Canada.
  • IlyinetsIlyinets is an impact structure about 8.5 km across near the town of Illintsi (Ilyinets) in Vinnytsia Oblast, central Ukraine. What it hit.
  • JänisjärviJänisjärvi is an impact structure about 14 km across in the Republic of Karelia, north-western Russia, filled by Lake Jänisjärvi, north of L
  • Jeokjung-Chogye BasinThe Jeokjung-Chogye Basin, in Hapcheon County in the south-east of South Korea, is a round basin about 7 km across ringed by mountains.
  • KaraThe Kara structure lies on the Arctic coast of Russia, at the northern end of the Pai-Khoi hills near the Kara Sea, west of the Ural Mountai
  • KarikkoselkäKarikkoselkä is a small impact crater about 1.4 km across, forming a round bay of Lake Päijänne in central Finland, near the town of Petäjäv
  • KentlandKentland is an impact structure about 7 km across in north-western Indiana, in the United States.
  • KeurusselkäKeurusselkä is a deeply eroded impact structure in central Finland, centred on the lake of the same name near the town of Keuruu.
  • LogoiskLogoisk is a buried impact crater about 15 km across near the town of Lahojsk (also spelled Logoisk), north-east of Minsk, in Belarus.
  • MansonManson, in north-west Iowa, is one of the largest impact structures in the United States, a crater about 35 km across hidden completely bene
  • MienMien is an impact structure about 9 km across in southern Småland, Sweden, whose centre is filled by the round Lake Mien. What it hit.
  • Mistastin (Kamestastin)Mistastin Lake, known to the Innu as Kamestastin, lies in the tundra and forest of northern Labrador, in eastern Canada.
  • MontagnaisMontagnais is a buried crater about 45 km across on the continental shelf off Nova Scotia, in eastern Canada.
  • MorokwengMorokweng, in South Africa's North West Province near the border with Botswana, is a large impact structure hidden beneath the sands of
  • NeugrundNeugrund is an impact crater about 8 km across on the floor of the Gulf of Finland, off the north-western coast of Estonia, near the island
  • NicholsonNicholson is an impact structure about 12.5 km across in the remote tundra of the south-eastern Northwest Territories, in Canada, mostly fil
  • Nördlinger RiesThe Ries is a crater people live in. Its floor is a broad, flat plain of farmland and villages in Bavaria, southern Germany, and at its hear
  • PopigaiPopigai, in the far north of Siberia, is one of the largest well-preserved impact craters on Earth.
  • Presqu'îlePresqu'île is a deeply eroded impact structure about 24 km across in the forests and lakes of central Quebec, in Canada, about 30 km nor
  • RitlandRitland is an impact crater about 2.7 km across in the mountains of Rogaland, south-western Norway, near the village of Ritland, east of Sta
  • RochechouartRochechouart, in the Limousin region of western France, is an impact structure that you cannot see as a crater at all.
  • Santa FeThe Santa Fe impact structure lies in the Sangre de Cristo Mountains just north-east of Santa Fe, the capital of New Mexico, in the United S
  • Santa MartaSanta Marta is an eroded impact structure about 10 km across in the state of Piauí, in north-eastern Brazil.
  • Slate IslandsThe Slate Islands are a group of islands in northern Lake Superior, off the town of Terrace Bay in Ontario, Canada.
  • SteinheimSteinheim, on the Swabian Alb in Baden-Württemberg, is the smaller sister of the Nördlinger Ries.
  • SudburySudbury in Ontario is one of the largest and oldest impact structures on Earth, and almost certainly the most valuable.
  • Suvasvesi NorthSuvasvesi North is an impact crater about 3.5 km across beneath Kuukkarinselkä, the northern part of the lake Suvasvesi in eastern Finland.
  • TswaingTswaing Crater lies about 40 km north-west of Pretoria in South Africa. It is one of the best-preserved young impact craters on Earth and on
  • Upheaval DomeUpheaval Dome, in Canyonlands National Park in Utah, is one of the most spectacular and debated structures in the American West.
  • Vista AlegreVista Alegre is an impact structure about 9.5 km across in the state of Paraná, southern Brazil.
  • VredefortVredefort is the largest confirmed impact structure on Earth, and one of the oldest.
  • Wells CreekWells Creek is an eroded impact structure about 12 km across in Houston and Stewart counties, northern Tennessee, in the United States.
  • ZapadnayaZapadnaya is a small impact crater about 3.2 km across in Zhytomyr Oblast, central Ukraine. Its name means 'western'. What it hit.
  • Zeleny GaiZeleny Gai is a small impact crater about 3.5 km across in Kirovohrad Oblast, central Ukraine. Its name means 'green grove'.

Impact events (8)

  • AcramanA crater found because its ejecta turned up 300 km away. Acraman is one of the few large impacts whose ejecta layer was discovered before an
  • Chesapeake BayA hidden crater that still affects the water people drink. In the late Eocene, an impactor struck the shallow sea off what is now the east c
  • LonarA crater lake in volcanic rock, sacred and ancient. Lonar is a nearly circular crater about 1.8 km across, holding a salty, alkaline lake.
  • ManicouaganA ring-shaped lake visible from space. Manicouagan in Quebec is one of the best preserved large impact structures on Earth.
  • Meteor Crater (Barringer Crater)The first crater on Earth shown to have been made by an impact. Meteor Crater is a bowl about 1.2 km across and 170 m deep in the desert of
  • The Ries and Steinheim impactsThe crater that proved impacts shape the Earth, and the source of moldavite. The Nördlinger Ries is a round, flat basin about 24 km across i
  • SudburyA giant impact that left one of the world's richest metal deposits. The Sudbury Basin in Ontario is the deformed remains of an impact cr
  • VredefortThe largest impact structure known on Earth. Vredefort is the biggest impact scar on our planet.

People (7)

  • Alan HildebrandThe Canadian scientist who, in 1991, identified the buried Chicxulub crater in Mexico as the impact that ended the age of the dinosaurs.
  • Carl AgeeThe New Mexico scientist who led the 2013 study of Black Beauty, a Martian breccia full of water-bearing minerals and ancient crust. Carl B.
  • Edward ChaoThe mineralogist who found coesite at Meteor Crater in 1960, the first proof that a crater on Earth was made by an impact.
  • Eugene ShoemakerThe founder of planetary geology, who proved Meteor Crater was an impact and co-discovered the comet that hit Jupiter.
  • Gustav TschermakThe Vienna mineralogist who named maskelynite, the shocked glass in the Shergotty meteorite, and helped classify meteorites.
  • Nevil Story-MaskelyneThe keeper of minerals at the British Museum who built up its meteorite collection and gave his name to maskelynite.
  • Robert DietzThe geologist who showed that shatter cones are fingerprints of impacts, and who argued that Sudbury in Canada is a giant impact structure.

Museums and collections (1)

  • Vredefort DomeThe deeply eroded remains of the largest known impact structure on Earth, a World Heritage Site.

Meteorites (the 60 largest of 215)