En naturlig fordybning eller hul i Jordens overflade, også kaldet en sink, shakehul, sinkhul, swallet, doline eller cenote, skyldes primært karstprocesser – den kemiske opløsning af karbonatbjergarter eller suffusionsprocesser, f.eks. i sandsten.
A natural depression or hole in the Earth's surface, also known as a sink, shake hole, sinkhole, swallow hole, swallet, doline or cenote, it is mostly caused by karst processes – the chemical dissolution of carbonate rocks or suffusion processes for example in sandstone.