It seems that giant sinkholes are not as rare as I thought. Another sinkhole opened in the Russian town of Berezniki on March 3, 2008.
The pictures are very impressive.
The sinkhole destroyed part of a road. Luckily, no one was on the road at the time. This makes me oif it’s practical to include some kind of ground-scanning radar in, say, annual surveys of roads for needed repairs. Any thoughts?
There was also a large sinkhole in Mexico that took three lives, but I haven’t found the date for it yet.