This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Sunday, March 27, 2016

New model for the Ries impact crater, Germany

I haven't worked much on meteorite impact craters for about 20 years, and have been delighted to find how much the concepts have changed since Chuck Simonds and I published our ideas about the role of volatiles and lithology in impacts back in 1980. The dramatic increase in our understanding results from two factors: over a half century of detailed work by (mostly) German geologists documenting the Ries in detail at all scales, and the dramatic increase in computational capacity since the 1980's. I reproduce here a figure from Stoffler et al. (2013) and a brief description of the five phases of an impact that they discuss. Strongly recommend the original papers. The impact scenario is for formation of the 24-kilometer Ries Crater in Germany, about 14.5 million years ago.  It's a favorite spot for meteorite enthusiasts, not the least because in the village of Nordlingen, a church is constructed from one of the impact products, suevite!

·      Phase 1, panel a: Impact phase, about 2 milliseconds after impact;
·      Phase 2, panel b: Primary ejecta plume and final shape of the transient cavity; ejecta curtain and clast-laden impact melt layer, about 10 seconds after impact;
·      Phase 3, panel c: fully developed primary ejecta plume, crater shape after collapse of transient cavity; formation of central uplift, and innermost ejecta blanket, the Bunte Breccia from deposition by the ejecta curtaint; about 40 seconds after impact, and
     Phase 3, panel d: buoyant primary ejecta plume begins collapsing,  deposition of Bunte     Breccia; slumping of volatile-containing sediments into the hot melt pool begins; about 2 minutes after impact
·      Phase 4, panel e: Secondary plume(s) formed by reaction of the hot melt pool with water for a fuel-coolant-interaction (FCI) process is fully developed, time = days to months;
·      Phase 4, panel f: Collapse of the FCI-induced secondary plume(s) and early phase deposition of outer suevite and part of crater suevite. Time = minutes to tens of minutes after start of FCI
·      Phase 4, panel g: late phase of secondary plume(s) and deposition of the main mass of crater suevite-time scale of months to years
·      Phase 5, panel h: final crater with all units in place, before formation of a crater lake if that happens. Time – months to years after impact.


    Kieffer,  S. and Simonds, C., The role of volatiles and lithology in the impact cratering process, Reviews of Geophysics and Space Physics, 18(1), 143-181, 1980.

    Stoffler, D., et al., Ries crater and suevite revisited--Observations and modeling Part I: Observations, Meteoritics and Planetary Science 48 (4), 515-589, 2013.

    Artemieva, N.A., Ries crater and suevite revisited--Observations and modeling Part II: Modeling, Meteoritics and Planetary Science 48(4), 590-627, 2013.