To date, approximately 190 impact craters have been recognized on Earth. However, impact craters on Earth provide the fundamental and unique opportunity to ground-truth the products of impact events. The study of impact processes and products is a multidisciplinary endeavor, synthesizing observations from the field, laboratory, and spacecraft, together with results of experiments and numerical modeling. This may have important implications for our understanding of the origin and evolution of early life on Earth, and possibly other planets, such as Mars. In recent years, it has also become apparent that, once formed, impact events also have certain beneficial effects, particularly for microbial life ( 5, 6). This is largely due to the discovery of the ~180-km-diameter Chicxulub impact structure, Mexico, and its link to the mass extinction event that marks the end of the Cretaceous period ~66 million years ago ( 4). The destructive geological, environmental, and biological effects of meteorite impact events are well known. It is also now apparent that impact events have profoundly affected the origin and evolution of Earth and produced benefits in the form of economic mineral and hydrocarbon deposits ( 3). Impact craters are one of the most common geological landforms on the majority of rocky terrestrial planets, asteroids, and many of the rocky and icy moons of the inner and outer solar system. Impact cratering is, arguably, the most important and fundamental geological process in the solar system ( 1, 2). Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. We have reestimated the diameter of eight well-known impact craters as part of this study. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. On the basis of field mapping, we derive the relationship D sc = 0.4 D a, where D sc is the maximum spatial extent of in situ shatter cones, and D a is the apparent crater diameter. Together with the occurrence of complete and “double” cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Despite this, there is still considerable debate regarding their formation. ![]() ![]() They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. Meteorite impact craters are one of the most common geological features in the solar system.
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