There are many natural processes other than impacts that can create circular features and depressions on the surface of the Earth. Examples include glaciation, volcanism, sinkholes, atolls, salt domes, intrusions, and hydrothermal explosions (to name just a few). Prehistoric mines and quarries are also sometimes mistaken for impact craters.
Although the USGS has been involved in impact crater research, we are neither the experts nor the ultimate authority on impact craters. Canada’s University of New Brunswick Planetary and Space Science Center is the best resource for confirming a structure as an impact crater. They maintain an Earth Impact Database and provide guidelines for identification of impact craters.
Learn more: This Dynamic Planet: World Map of Volcanoes, Earthquakes, Impact Craters, and Plate Tectonics
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Although extremely unlikely, it might be possible for a reversal of the Earth's magnetic field to be triggered by a meteorite or comet impact, or even for it to be caused by something more "gentle," such as the melting of the polar ice caps. Self-contained dynamic systems like Earth’s dynamo can have reversals without any outside influence. Reversals of Earth's magnetic field can simply happen...
What is a sinkhole?
A sinkhole is a depression in the ground that has no natural external surface drainage. Basically, this means that when it rains, all of the water stays inside the sinkhole and typically drains into the subsurface. Sinkholes are most common in what geologists call, “karst terrain.” These are regions where the types of rock below the land surface can naturally be dissolved by groundwater...
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The U.S. Geological Survey Astrogeology Science Center
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- FAQ
Could magnetic reversals be caused by meteorite or comet impacts?
Although extremely unlikely, it might be possible for a reversal of the Earth's magnetic field to be triggered by a meteorite or comet impact, or even for it to be caused by something more "gentle," such as the melting of the polar ice caps. Self-contained dynamic systems like Earth’s dynamo can have reversals without any outside influence. Reversals of Earth's magnetic field can simply happen...
What is a sinkhole?
A sinkhole is a depression in the ground that has no natural external surface drainage. Basically, this means that when it rains, all of the water stays inside the sinkhole and typically drains into the subsurface. Sinkholes are most common in what geologists call, “karst terrain.” These are regions where the types of rock below the land surface can naturally be dissolved by groundwater...
When did dinosaurs become extinct?
Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years. If all of Earth time from the very beginning of the dinosaurs to today were compressed into 365 days (one calendar year), the dinosaurs appeared January 1 and became extinct the third week of September. (Using this same time scale, the Earth would have formed...
Did people and dinosaurs live at the same time?
No! After the dinosaurs died out, nearly 65 million years passed before people appeared on Earth. However, small mammals (including shrew-sized primates) were alive at the time of the dinosaurs. Some scientists who study dinosaurs (vertebrate paleontologists) now think that birds are direct descendants of one line of carnivorous dinosaurs, and some consider that they in fact represent modern...
I think I found a meteorite. How can I tell for sure?
Meteorites are fragments of rock or metal that fall to Earth from space. They are very rare, but many people find unusual rocks or pieces of metal and wonder if they might have found a meteorite. Meteorites have several properties that help distinguish them from other rocks: Density: Meteorites are usually quite heavy for their size, since they contain metallic iron and dense minerals. Magnetic...
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The U.S. Geological Survey Astrogeology Science Center
In 1960, Eugene Shoemaker and a small team of other scientists founded the field of astrogeology to develop tools and methods for astronauts studying the geology of the Moon and other planetary bodies. Subsequently, in 1962, the U.S. Geological Survey Branch of Astrogeology was established in Menlo Park, California. In 1963, the Branch moved to Flagstaff, Arizona, to be closer to the young lava flAuthorsLaszlo P. Kestay, R. Greg Vaughan, Lisa R. Gaddis, Kenneth E. Herkenhoff, Justin HagertyChesapeake Bay impact structure: A blast from the past
About 35 million years ago, a 2-mile-wide meteorite smashed into Earth in what is now the lower Chesapeake Bay in Virginia. The oceanic impact vaporized, melted, fractured, and displaced rocks and sediments and sent billions of tons of water, sediments, and rocks into the air. Glassy particles of solidified melt rock rained down as far away as Texas and the Caribbean. Large tsunamis affected mostAuthorsDavid S. Powars, Lucy E. Edwards, Gregory S. Gohn, J. Wright HortonStudies of the Chesapeake Bay impact structure: The USGS-NASA Langley corehole, Hampton, Virginia, and related coreholes and geophysical surveys
No abstract available.AuthorsJ. Wright Horton, David S. Powars, Gregory S. GohnThe effects of the Chesapeake Bay impact crater on the geologic framework and the correlation of hydrogeologic units of southeastern Virginia, south of the James River
About 35 million years ago, a large comet or meteor slammed into the shallow shelf on the western margin of the Atlantic Ocean, creating the Chesapeake Bay impact crater. This report, the second in a series, refines the geologic framework of southeastern Virginia, south of the James River in and near the impact crater, and presents evidence for the existence of a pre-impact James River structuralAuthorsDavid S. PowarsThe Chesapeake Bay bolide impact: a new view of coastal plain evolution
A spectacular geological event took place on the Atlantic margin of North America about 35 million years ago in the late part of the Eocene Epoch. Sea level was unusually high everywhere on Earth, and the ancient shoreline of the Virginia region was somewhere in the vicinity of where Richmond is today (fig. 1). Tropical rain forests covered the slopes of the Appalachians. To the east of a narrow cAuthorsC. Wylie PoagChicxulub impact event; computer animations and paper models
AuthorsT. R. Alpha, John P. Galloway, S. W. StarrattGold in meteorites and in the earth's crust
The reported gold contents of meteorites range from 0.0003 to 8.74 parts per million. Gold is siderophilic, and the greatest amounts in meteorites are in the iron phases. Estimates ,of the gold content of the earth's crust are in the range of 0.001 to 0.006 parts per million.AuthorsRobert Sprague JonesImpact mechanics at Meteor Crater, Arizona
Meteor Crator is a bowl-shaped depression encompassed by a rim composed chiefly of debris stacked in layers of different composition. Original bedrock stratigraphy is preserved, inverted, in the debris. The debris rests on older disturbed strata, which are turned up at moderate to steep angles in the wall of the crater and are locally overturned near the contact with the debris. These features ofAuthorsEugene Merle ShoemakerMeteoroids and impact craters
On a clear night scores of meteoroids streak across the sky. they leave light paths we call meteors or shooting stars as the Earth is showered with debris from distant parts of the solar system. When these meteoroids hit the Earth (as meteorites) they range in size from pebbles to the 34 ton Ahnighito meteorite that the American explorer Admiral Robert Peary discovered in Greenland. The unique impAuthorsHenry Spall - News