An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters are typically circular, though they can be elliptical in shape or even irregular due to events such as landslides. Impact craters range in size from microscopic craters seen on lunar rocks returned by the Apollo Program to simple bowl-shaped depressions and vast, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.
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.
The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community of Chicxulub Pueblo. It was formed slightly over 66 million years ago when an asteroid, about ten kilometers in diameter, struck Earth. The crater is estimated to be 200 kilometers in diameter and 1 kilometer in depth. It is believed to be the second largest impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research.
The Nördlinger Ries is an impact crater and large circular depression in western Bavaria and eastern Baden-Württemberg. It is located north of the Danube in the district of Donau-Ries. The city of Nördlingen is located within the depression, about 6 kilometres (3.7 mi) south-west of its centre.
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.
The Boltysh crater or Bovtyshka crater is a buried impact crater in the Kirovohrad Oblast of Ukraine, near the village of Bovtyshka. The crater is 24 kilometres (15 mi) in diameter and its age of 65.39 ± 0.14/0.16 million years, based on argon-argon dating techniques, less than 1 million years younger than Chicxulub crater in Mexico and the Cretaceous–Paleogene boundary. The Chicxulub impact is believed to have caused the mass extinction at the end of the Cretaceous period, which included the extinction of the non-avian dinosaurs. The Boltysh crater is currently thought to be unrelated to the Chicxulub impact, and to have not generated major global environmental effects.
The Glasford crater, also known as the Glasford Disturbance, Glasford Structure, and Glasford Cryptoexplosion Structure, is a buried impact crater in southern Peoria County, Illinois, in the United States. It is one of two known meteor craters in Illinois.
Kaali is a group of nine meteorite craters in the village of Kaali on the Estonian island of Saaremaa. Most recent estimates put its formation shortly after 1530–1450 BC. It was created by an impact event and is one of the few impact events that has occurred in a populated area.
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.
Puchezh-Katunki is a meteor crater located in the Nizhny Novgorod Oblast of the Volga Federal District, Russia. It is 80 km (50 mi) in diameter. Argon–argon dating has constrained the age of formation to be 195.9 ± 1.0 million years old, placing it within the Sinemurian stage of the Early Jurassic. The crater is not exposed to the surface, but appears as variation in the vegetation. The Earth Impact Database lists a rim-to-rim diameter of 40 kilometres (25 mi).
Pantasma is a region in the north of Nicaragua. In the Miskito language the word Pantasma means small humans or flat head. The Spanish word Fantasma origins from the Greek Phantasma and means ghost.
The Australasian strewnfield is the youngest and largest of the tektite strewnfields, with recent estimates suggesting it might cover 10%–30% of the Earth's surface. Research indicates that the impact forming the tektites occurred around 788,000 years ago, most likely in Southeast Asia. The probable location of the crater is unknown and has been the subject of multiple competing hypotheses.
The Siljan Ring is a prehistoric impact structure in Dalarna, central Sweden. It is one of the 15 largest known impact structures on Earth and the largest in Europe, with a diameter of about 52 kilometres (32 mi). The impact that created the Siljan Ring occurred when a meteorite collided with the Earth's surface during the Devonian period. The exact timing of the impact has been estimated at 376.8 ± 1.7 Ma or at 377 ± 2 Ma. This impact has been proposed as a cause of the first Devonian extinction, the Kellwasser Event or Late Frasnian extinction, due to it being believed by some researchers to coincide around the time of the Kellwasser event at 376.1 Ma ± 1.6 Ma, although the timing of this extinction event has since been pushed forward to 371.93–371.78 Ma. The effects of the impact can clearly be seen in the bedrock in the area. The Cambrian, Ordovician and Silurian sedimentary rocks deformed by the impact are rich in fossils.
Ramgarh crater, also known as Ramgarh structure, Ramgarh Dome and Ramgarh astrobleme, is a meteor impact crater of 3.5 kilometres (2.2 mi) diameter in Kota plateau of Vindhya Range located adjacent to Ramgarh village, 40 km north of Baran City in Mangrol tehsil of Baran district in Indian state of Rajasthan. When formally accepted as the third crater in India, its diameter size would be between the two already confirmed craters in India - Dhala in Madhya Pradesh with 14 km diameter and Lonar in Buldhana district of Maharashtra with 1.8 km diameter.
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.
As of June 2018, 12 confirmed impact structures have been found in Finland. They are listed below, sorted by original diameter.
