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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When I first heard of that Florida building collapse, my first thought was sinkhole. We know those things happen there: the landscape has limestone formations all over the place. Limestone is calcium carbonate. Its solubility under pressure is greater than when not under pressure. I assumed that the tower put more pressure on a limestone formation that eventually gave out after 40 yrs.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Now I hear something weird. Someone who perished on the 4<sup>th</sup> floor was on the phone with her husband when she reported that the swimming pool was gone. OK sinkhole (rather than salt air degrading steel structure (which I never believed (because plenty of places have both salt spray and steel (and prevailing winds push most of that out to see from Miami (and buildings have a huuuuuge safety margin, huge, overkill (but it doesn’t matter how big is the structural margin if the ground below the building gives out.))))) But I would assume the pressure on the limestone below the building would be way higher than the pressure below the pool. So now I don’t understand.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Sheesh, sinkhole takes down condo. Helva note.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>spike<o:p></o:p></p></div></body></html>