by: Charles O’Dale
The scientific study of impact structures began only about 50 years ago. I’m dating myself, but that was about the time my interest in impact craters started. Like any kid, I spent hours looking at the craters on the Moon through my old telescope. Would I ever get a chance to explore a crater? Well since retirement, I combined my hobbies of astronomy, geology and flying to explore impact craters and structures in North America from the air and ground. You may think that the natural geological forces on our planet would have destroyed any features of impact craters. But, in some instances, these forces have “cross sectioned” the craters to ease our study. I find the geology in these craters and structures fascinating!
While studying the physics of impact sites, I have found that circular geological features can be produced by a number of geological processes, including igneous activity (diatremes, maars, calderas, volcanoes, or syenite/plutons), dissolution and collapse of salt or carbonate rocks by groundwater (dolines), salt or shale diapirism, regional tectonism (circular fold-interference patterns or stratified circular features), glaciation (kettle holes), carbonate mounds, and by meteorite impacts (Stewart 2003). You can see below some of the non-impact structures that I have explored over the past few years.
Stewart S. A. 2003. How will we recognize buried impact craters in terrestrial sedimentary basins? Geology 31:929–932.
My science background plus the experience that I have gleaned from my past profession of semiconductor failure analysis has given me the incentive to document my analysis of these craters and structures. I encourage anyone to please contact me if they note any errors that I may have made in my documentation or if they have something to add. (A few of my expeditions actually resulted from suggestions made from readers of this site).