February Geology and GSA Today media ...(t can be invoked to recognize high-veloc...)

The Lake St. Martin bolide has a big impact on groundwater fluoride concentrations
Matthew I. Leybourne et al., GNS Science, Lower Hutt, New Zealand. Pages 115-118.

Meteor impact is popularly linked with catastrophic extinction events, but some effects can be harmful in a more subtle and insidious manner. As Leybourne shows, the shattering impact of a meteor on rocks results in increased groundwater-rock surface interaction. This has a direct effect on the quality of the groundwater that percolates through the fractured, melted rocks of the impact structure. A good example has been found at the Canadian town of Gypsumville, Manitoba (population 65), located near the Lake St. Martin meteor impact crater. Domestic wells in the town have elevated salinity, sulfate, and fluoride concentrations. The fluoride, which exceeds health limits, is of concern as excess intake causes mottling of teeth at moderate levels, to softening of bones and neurological damage at higher levels. The groundwater with elevated fluoride is shown to occur exclusively within the impact structure, and Leybourne's study is thought to be the first to document enhanced groundwater fluoride concentrations associated with impact structures.

Ridge reorientation mechanisms: Macquarie Ridge Complex, Australia-Pacific plate boundary
Sharon Mosher, Department of Geological Sciences, The University of Texas at Austin, 1 University Station C1100, Austin, Texas 78712-0254, USA; and Christina Symons, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093, USA. Pages 119-122.

Mosher and Symons analyzed a unique, complete seafloor record to document the processes associated with the transition of the Australia-Pacific tectonic plate boundary south of New Zealand from an oceani
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