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

Thursday, May 17, 2012

The biggest sandbox in the world....?

 A: Seismic section with gamma-ray log
 B, C: Samples from upper part of upper sand
(white arrow in SWC in A)
(I'm being a bit lazy here, because I'm working on a PC instead of my trusty Mac and can't figure out even the simplest operations, so I'm  just cutting-pasting in directly from this very interesting article in Geology "World's largest extrusive body of sand?" by Helge Loseeth, Nuno Rodrigues, and Peter Cobbold,Geology, 40(5), 467-470, 2012 )

During the 1812 New Madrid earthquake (southeastern United States), individual bodies of sand as much as 2 m thick appeared patchily over a 4000 km2 area. The sand volume was estimated to be to be 105–107 m3 and there were claims that it was the largest reported extrusive sand (extrudite). There have been no reports of extrusive sands as voluminous as several cubic kilometers. Typically, extrusive sands connect to their parent sandbody or sandbodies in the subsurface via hydraulic fractures.

Using three-dimensional seismic and well data from the northern North Sea, Loseth and colleagues describe a large (10 km3) body of sand and interpret it as extrusive. To their knowledge, this is the world's largest such sandbody. It would bury Manhattan, New York (60 km2), under 160 m of sand, or the whole of London, UK (1579 km2), under 6 m of sand. This sand vented to the seafloor, when it was more than 500 m deep, during the Pleistocene glacial period. The sandbody (1) covers an area of more than 260 km2, (2) is up to 125 m thick, (3) fills low areas around mounds, which formed when underlying sand injectites lifted the overburden, (4) wedges out, away from a central thick zone, (5) is locally absent along irregular ditches, 20 km long and up to 50 m deep, which overlie feeders on the flanks of the mounds, and (6) consists of fine-grained to medium-grained, sub-rounded to rounded grains.

A pretty big sandbox to play in!!

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