Places I've been: Umpherston Sinkhole, Mt Gambier, South Australia

 

While I was in Mt Gambier a while ago, I got the opportunity to visit the Umpherston Sinkhole. Located within 5 minutes of the CBD, the sinkhole is very approximately 50m deep. Originally  beautified by James Umpherston in 1886, the sinkhole has been replanted to restore it's original format. In the past I've seen both tame possums begging for apple scraps and a clutch of random guinea pigs racing around the base of the sinkhole.

 

The sinkhole originally formed through the dissolution of calcite from the limestone. This slowly created a cave. The roof eventually fell in on the northern side allowing meteoritic water into the sinkhole. This aided further dissolution resulting in a slope to the base of the sinkhole. Further collapses opened up the hole to the size seen today. The tourist signs around the sinkhole indicate there was originally a lake that took up a good portion of the hole but this has disappeared with the lowering of the local water table. The lowest point of the sinkhole seems to remain damp which suggests additional collapses may be on the horizon.

 

The gardens are lovely, and the early morning sunlight allowed me to take the above image. It looks so much like a nature documentary!