About This Website
This steadily expanding website presents a list of known and possible impact crater location within the United States, as well as a few pages that are intended to provide a basic introduction to impact crater science and to the methods and techniques behind the identification of terrestrial impact craters. The website is written and curated as a research resource by Robert Beauford, Ph.D., with the much appreciated assistance of reviews and comments from users. (send comments to: ).
Understanding and mitigating ongoing asteroid impact risk
The solar sytem is not a neat and clean place. There are literally billions (French, 1998) of large objects whirling around the sun. Some of these share common or similar orbits with earth or the other inner planets. Many others lie in the asteroid belt between Mars and Jupiter. A vastly larger number form the Kuiper belt and Oort cloud at the outer edges of the solar system. To say that the earth has been heavily impacted in its history is a profound understatement. The planet is, in fact, an accumulation of 6 trillion-trillion kilos of material, all of which accreted through impacts at one scale or another.
What this implies for the future can be a bit scary. Small impacts are constant. Impacts large enough to create small (<100 meter) craters seem to occur at least once a century, and possibly more frequently. Impacts capable of destroying a large city are about as common as extreme (but not the most extreme!) volcanic events. Regionally destructive impacts, capable of permanently altering the destiny of any small nation in which they occur, appear to happen at an interval between less than 50,000 and a million years, meaning that several have occured in the time since humanity began its climb from incoherent australopithecines, just a few million years ago, to become the sublime creators of daytime. And the 'big ones' - planet killing, civilization ending impacts approaching or exceeding the scale of the KT (or K-Pg) boundary impactor that killed off the dinosaurs - occur about once every hundred million years, while their smaller, but still globally significant, companions traipse in at intervals measured in the tens of millions of years or less. In other words, impacts capable of utterly and irrevocably ending 'life as we know it,' permanently altering the future course of humanity, or altering the destinies of nations, have occured 1000s of times since life appeared, well over 3 billion years ago. Understanding the nature and scope of this threat is an effort worth making, expecially considering that the exploration that is involved offers its own shorter-term rewards.
Resource recovery on Earth and in space
The world's impact structures have played repeated and important roles in geophysical exploration for oil, gas, coal, rare earth elements, copper, nickel, barium, zinc, iron, silver, gold, platinum, and water. Resource producing impacts include the Sudbury structure, which is one of the planet's leading current sources of nickel and copper!
The materials from which planets and asteroids are composed start out thoroughly mixed. Ores and 'resource' mineral deposits are natural concentrations of useful atoms. Even on earth, finding these natural concentrations is hard. Because they produce prolonged localized heating and provide both conduits and energy to drive long-term hydrothermal systems, Earth's impact craters have produced some of the planet's most productive ore bodies and other resource concentrations. To exist in space, on any significant scale, humanity is going to find it necessary to find, recover and refine resources on other planets and among the solar system's smaller bodies. Impact melting and impact heat driven aqueous fluid systems are the solar system's most likely concentrators of off-planet useable resources.
Impacts have been a fundamental geological process throughout the planet's history. As such, they teach us a significant amount about the interior and history of our planet.
Modern geophysical exploration does not stop at the surface of the planet earth. Without the corollary field of meteoritics and impact science, we would have nothing against which to normalize data, no conception of the deep interior of the planet, no understanding of the planets ancient or modern internal heat budget, and no real conception of geochemical differentiation at a planetary scale.
The largest-scale and most broadly applied refining and concentration process in the solar system is (or was) the process of planetary differentiation. Every large object in the solar system, including very large asteroids, moons, and planets, has undergone a process of melting and sorting at a large scale that is termed planetary differentiation. Oversimplified and stated in brief, differentiation is the process during which large objects in the early solar system melted and seperated into dense, iron rich cores, heavy silicate mantles, and more-or-less light silicate crusts. This happened because the early solar system was rich in short lived radioactive isotopes of aluminum and iron. These are essentially all gone now. The decay of these radionuclides produced heat. Large bodies do not shed heat as effectively as small bodies, so they heated up to the temperatures necessary to melt. When they melted, the iron, along with various atoms that associate with iron, largely sank to the center. Heavy iron and magnesium rich silicates floated on top of this iron, and light feldspars, aluminum, calcium, and sodium rich silicates, floated at the planetary surface.
Recommended Initial Reading:
Anyone wishing to develop an in depth undertanding of the scientific study of meteorite impact craters would do well to begin by reading Bevan French's book, 'Traces of Catastrophe,' and Osinski and Pierazzo's (editors) recent volume 'Impact Cratering Processes and Products'. Each of these provides an excellent overview of the subject of impact crater science, and just as important, each contains a substantial bibliography of more in-depth literature. They provide a solid, modern introduction to the scientific discipline.
The impactcraters.us website is continually changing and growing for several reasons. This resource is intended as a research tool and up to date compendium of information on impact craters located within the United States. The aim of this project is to provide a current catalog of known impact craters for the United States region that is as accurate as possible, based on diagnostic evidence of hypervelocity impact published in scientific literature. It is hoped that this may support global projects in the same vein, such as the (PASSC database and Meteoritical Bulletin database). The intended scope of the project is large - to provide and accurate catalog with basic metrics, a literature review, and a complete annotated bibliography for each site, with a visitor's guide and field-trip introduction to each of the ones that is exposed (not buried). This means that the project includes ovber 150 years of research on nearly 30 sites, with extensive travel and the necessity of reading and reviewing many thousands of pages of text. Though the effort remains incomplete and imperfect, it is hoped that it will have utility to researchers and educators, and that it may be engaging for students and the general public. Because of both the scope of the project and the fact that it is intended to provide ongoing and expanding utility, rather than a momentary snapshot of the field, that it will remain a 'work in progress' for an indefinite time.
This website resource is divided into TWO parts: A Guidebook to the Meteorite Impact Craters and Structures of the United States, an ongoing review and guide to the geological literature surrounding those reasonably well supported impact craters that are best supported by evidence within the U.S., and a second book Introduction to Impact Craters and Their Identification, intended to provide an introduction to the history and current research behind the recognition of impact craters as geological structures.
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