The Chieming-Stöttham archeological excavation – comments on a recently published article

by Chiemgau Impact Research Team (CIRT)

Abstract: – At the behest of the Bavarian State Office for Monument Preservation (BLfD) the archeological excavation at Stöttham near Lake Chiemsee, which exposed an intercalated geological layer with all evidence of a catastrophic deposition in a meteoritical impact event, was accompanied by a study performed by Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt der Technischen Universität München [Science Center of Nutrition, Land Use and Environment, Technical University of Munich, at Weihenstephan]. In the now published article the exposure is most widely described and interpreted from a geomorphological and soil science perspective while the unambiguous impact features implying the typical heavy rock deformations and shock metamorphism (shock effects) are completely ignored. Nevertheless, the authors conclude that there are not any indications of an impact event. Here, we remind of the progress of events, discuss the major shortcomings of Völkel et al.’s article, and conclude that it doesn’t meet scientific requirements. Continue reading “Chiemgau Impact – a new article: Jörg Völkel, Andrew Murray, Matthias Leopold, and Kerstin Hürkamp: Colluvial filling of a glacial bypass channel near the Chiemsee (Stöttham) and its function as geoarchive. – Zeitschrift für Geomorphologie (Annals of Geomorphology), 56(3), 371-386, 2012.”

… or a “Requiem” for the rejection of the hypothesis?

YDB abbreviates Younger Dryas Boundary. The Younger Dryas stadial signifies a sharp onset of a period of cold climatic conditions in Earth’s history lasting roughly 1,000 years  between about 11,000 and 10,000 B.C. at the end of the Pleistocene (the “Ice Age”) and the beginning Holocene.

The causes of this event are controversially disputed, and they are conventionally ascribed to perturbations of  North Atlantic circulation. In 2007, a new hypothesis on a giant meteorite impact  Continue reading “YDB impact: a new chapter”

The term spallation is used in various meanings, e.g. in nuclear physics and fracture mechanics. For impact processes, spallation plays an important role (however seldom appreciated appropriately) and is closely related with the propagation of shock waves. To put it simply, the process runs as follows: On impinging on a free surface, the shock compressive wave is reflected as a tensile wave of practically identical energy. And while a compressive pulse is squeezing a rock, a tensile pulse is stretching the material thus enabling the development of tensile fractures and in an extreme case leading to the detachment of a spall or series of spalls. This is favored by the fact that the tensile strength of all materials and, hence, also of rocks is considerably less than the compressive strength. This is why it is often disregarded that the enormous destructions upon meteorite impact are not so much the result of the shock wave pressure as of the pull of the rarefaction waves. Spallation may take place also when a compressive shock pulse impinges on a boundary of material with reduced impedance (= the product of density and sound velocity) where part of its energy is reflected as a rarefaction pulse that may likewise enable tensile fracturing. It is worth remarking, however compatible with shock physics, that the process of spallation can be observed on arbitrary scales, from microscopically small deformations right up to the movement of huge rock complexes.

Fig. 1. A limestone cobble (14 cm long) exhibiting the typical open spallation tensile fractures. The process is nicely documented by the observation that the running fractures have come to standstill midway through the cobble. In case they had continued running, the cobble would have been fractionized to pieces, and nothing of note would have remained. Continue reading “Shock spallation – a typical impact process in the Chiemgau meteorite crater strewn field”