Sinkhole Theory

Was wondering why many sinkholes seem to be round. My simple theorised answer… A circular shape is a shortest distance from point A of weakness back to point A itself, that leads to collapse of the enclosed area. Nature always takes the path of least resistance. Think lightning striking the most strikable, water flowing around obstacles…

How about another wild theory – ‘black holes’. Excess materialism above (buildings and such) and below (tunnels and such) collapsing upon itself. Just kidding? Now, Singapore has its own natural disaster? The ground below might just give way. (The picture features Kuwait though.)