Is the engineering explanation that the roadway was built dependent upon gravity, with no attachments - or effective attachments - to prevent even mild upward lift?  

Christopher
 
The new mode of belief/understanding would describe it as "Intelligent Rising".   See yesterday's posting with a link to The Onion. http://www.theonion.com/content/node/39512
 
cp in bc
where snow still falls by its own choice