In 1972 H. G. Wilshire et al published a paper for NASA titled . Geology of the Sierra Madera Cryptoexplosion Structure, Pecos County, Texas.
One of the major problems with getting a good handle on the impact record of the past is in the naïve assumption that round craters from the direct kinetic impact of a solid object hitting the ground are the only possible planetary scarring we should expect to find.
We are only now beginning to realize that very large airbursts might be capable of significant geologic change. And that the planetary scarring of such an event will have no resemblance whatsoever to an impact crater.
Wilshire et al didn’t have access to high resolution satellite imagery. If they had, they might have noticed that it is a close match for some structures just across the border in North Central Mexico, and that are in almost perfectly pristine condition.
Folks might note that the patterns of motion in the emplacement of the blast-effected materials at the Sierra Madera cryptoexplosion structure, and the numerous pristine examples like it across the border that are in even better condition, i.e. radial outwards at the periphery, and inwards and upwards, at the center, are a perfect match for the bottom of an ablative airburst vortex such as the ones depicted in Mark Boslough’s supercomputer simulations.
In 1972 Wilshire et al could never have imagined that an airburst such as the Tunguska event of 1908 could be large enough to produce significant geologic change. And since the only models for an impact structure they could imagine were the craters we see on the moon and Mars, they assumed without question that it was caused by the impact of a solid object. And they explained the lack of a crater rim by proposing that the explosive event happened in the Late Cretaceous or early Tertiary. And that the crater rim has eroded away in the millions of years since.
But using high resolution satellite imagery, a careful study of the radial patterns of flow in the emplacement of the fluidized flows of breccias and clastic materials surrounding the central uplift of it, and others like it across the border in Mexico will reveal that the structure is in almost pristine condition, and that it was never a crater with a rim.
The entire region is imaged to a resolution of better than 1 meter per pixel in Google Earth; good enough to count the number of cattle a rancher has on his place. And good enough to recognize and read the directionality of emplacement in pyroclastic materials on the surface like following spilled paint back to the can. If the structure were as old as Wilshire et al thought, the patterns of fluid motion in the flows of pyroclastic material at Sierra Madera, and places like it across the border would’ve been erased millions of years ago along with any ring structures. Yet those radial flows of breccias, and pyroclastic material surrounding the central uplifts are virtually undisturbed, and on the surface; a fact that argues for a much younger age for the explosive events that put them there.
Wilshire et al didn’t use any radiometric data. And in 1972 they were still working from the assumption that all impact structures are the result of the impact of a solid object. They couldn’t have imagined that an airburst might be capable of significant geologic change. So their estimate of great age is based on the assumption that enough time has passed to erode away a crater rim. There is no mention of isotopic analysis of specimens from there. But it would be interesting to take a piece of rock that was melted in one of those events, check for ET isotopes, and try to get a definitive age since melt from it.
Once you recognize the real nature of the above ground explosive event that formed the Sierra Madera structure, and its sisters across the border, you also come to the realization that the blast-effected materials of the event, i.e. the radial outwards flowing emplacements of fluidized flows of pyroclastic rock, and breccias, surrounding a central uplift of shatter cones, and blast effects pointing inwards, and upwards, are not the result of a sold object hitting the ground. And that fact forces the conclusion that, contrary to the uniformitarian/gradualist assumptive theory for the mechanics if its formation as expressed by Wilson et al, There never was a crater rim to erode away. The ground at Sierra Madera wasn’t heavily eroded over millions of years, it was heavily ablated over a period of just a few seconds in a large, ablative airburst event. The condition of the blast-effected materials of that above-ground explosion are, in fact, almost perfectly pristine, and they remain virtually undisturbed on the surface since the explosion that put them there. Whatever else the Sierra Madera structure is, geologically old it isn’t.