Sinkholes are fairly common, due to collapsed caves, old mines or dissolving material, but the circumstances in South Dakota ...
Sinkholes are fairly common, due to collapsed caves, old mines or dissolving material, but the circumstances in South Dakota stand out, said Paul Santi, a professor of geological engineering at the ...
Sinkholes are fairly common, due to collapsed caves, old mines or dissolving material, but the circumstances in South Dakota ...