[meteorite-list] Re: "Round Rocks" from Osceola, Missouri Impact Site
From: Mr EMan <mstreman53_at_meteoritecentral.com>
Date: Sun Aug 20 03:42:42 2006 Message-ID: <20060820074229.7609.qmail_at_web51012.mail.yahoo.com> Interesting follow up note as I Google about trying to visualize the dynamics and avoid broaching the "T word"--tektite. The article below speaks of them being shale kernals which upon falling back into the melangue over time became "chert concretions". I also noted that one of the affected formations is the Keokuk limestone of geode fame. "Missouri rock balls. One of the largest meteorite craters in the United States is in the state of Missouri where a rock 1,200 feet in diameter plunged into Earth's atmosphere sometime around 310 to 340 million years ago. It crashed into territory where we find the modern towns of Weaubleau and Osceola. The impact crater encircles the modern community of Vista, making it one of only two U.S. communities, along with Middlesboro, Kentucky, totally encircled by a meteorite crater or crater remnants, according to geologist George H. Davis, a member of the team that used shallow core drilling to investigate the Weaubleau-Osceola meteorite impact in July 2003. Osceola and Weaubleau are not within the impact crater. Geologists say such a quarter-mile-wide meteorite could explain how some rocks they found on the ground had come to be folded over and other rocks containing shattered quartz had ended up in the Ozark Mountains. Residents of the area around Osceola have found a lot of strange, perfectly-round rocks. Geologists theorize the round stone balls are chert concretions. They suggest the impact blasted up gravel-sized pieces of shale that fell back to the ground. Silica-rich solutions seeped in around the small shale pieces and hardened in place. Those chert concretions are evidence that the impact actually occurred, according to Davis. The folded rocks are visible in a local quarry and Davis describes them as "fascinating." The team of geologists theorize that the folding happened in "mere milliseconds." Their drilling into the structure turned up one large piece of granite that had been lifted nearly 1200 feet vertically through rock and sediment by the force of the impact." Ercerpted from: <http://www.spacetoday.org/SolSys/Earth/Meteorites/MeteoritesExplained.html> Elton Received on Sun 20 Aug 2006 03:42:29 AM PDT |
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