Paper No. 1
Presentation Time: 1:30 PM
What Can We Learn from Meteor Crater Regarding the Origin, Structure, and Evolution of Impact Craters on Earth?
Meteor Crater is the world's best preserved impact crater with a simple bowl-like morphology and is, thus, a benchmark for understanding impact cratering processes. Studies by D.M. Barringer, B.C. Tilghman, H.H. Nininger, E.M. Shoemaker, and E.C.T. Chao demonstrated that the structure has several unique features that prove an impact rather than volcanic origin: uplifted bedrock in crater walls, an overturned sequence of target strata on the crater rim and in an ejecta blanket, an interior breccia lens, impactor components within that breccia lens and the ejecta blanket, shock-metamorphic deformation of target materials, including the transformation of quartz to coesite and stishovite, and melt mixtures of target materials and the impactor. Traditionally, the structure was studied in terms of the geologic processes involved, but we now realize that impact cratering can affect the environment and, potentially, the biologic evolution of Earth. Meteor Crater has, thus, become a tactile example of an impact event in a well-understood environment and provided new insights about an impact's effects. Because this size event is more common than larger events, the crater also provides a measure of the modern hazard of an impact event, which is sufficient to destroy a city. There are still several geologic issues that need to be resolved at the impact site, including the asteroid trajectory and energy required to excavate the crater, the extent of subsurface target rock fragmentation, and the abundance of impacting material that was injected into those subsurface fractures. Consequently, Meteor Crater remains an exciting site for terrestrial crater research and is also proving to be a particularly interesting analogue structure for craters being explored on the Moon and Mars.