page_title: Breccia
section_title: Impact
hierarchical_section_title: Breccia / Types / Impact
caption_attribution_description: English: Alamo impact breccia (Late Devonian, Frasnian) near Hancock Summit, Pahranagat Range, Nevada.
context_page_description: Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments.
  The word has its origins in the Italian language, in which it means either "loose gravel" or "stone made by cemented gravel". A breccia may have a variety of different origins, as indicated by the named types including sedimentary breccia, tectonic breccia, igneous breccia, impact breccia, and hydrothermal breccia.
  A megabreccia is a breccia composed of very large rock fragments, sometimes kilometers across, which can be formed by landslides, impact events, or caldera collapse.
context_section_description: Impact breccias are thought to be diagnostic of an impact event such as an asteroid or comet striking the Earth and are normally found at impact craters. Impact breccia, a type of impactite, forms during the process of impact cratering when large meteorites or comets impact with the Earth or other rocky planets or asteroids. Breccia of this type may be present on or beneath the floor of the crater, in the rim, or in the ejecta expelled beyond the crater.
  Impact breccia may be identified by its occurrence in or around a known impact crater, and/or an association with other products of impact cratering such as shatter cones, impact glass, shocked minerals, and chemical and isotopic evidence of contamination with extraterrestrial material (e.g., iridium and osmium anomalies). An example of an impact breccia is the Neugrund breccia, which was formed in the Neugrund impact.
caption: Alamo bolide impact breccia (Late Devonian, Frasnian) near Hancock Summit, Pahranagat Range, Nevada
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