While visiting Mt Gambier, we can across some sinkholes which the boys loved. In the Umpherston Sinkhole, we were able to feed some cute possums at night which was a favourite part of our Lap of Oz.
But visiting these sinkholes also brought up a lot of questions from the boys about what they are and how they are created.
First, we talked about what a sinkhole is and how they come about.
A sinkhole is a hole or depression in the ground caused by the surface layer collapsing.
Then we looked through our photos of the sinkholes we visited while in Mt Gambier, before moving onto making our sugar cube sinkhole.
To make this sinkhole, you will need:
Arrange the sugar cubes against the side of your clear container. Our sugar hill was 3 (sugar cubes) x 3 x 3
Completely cover the outside of the cubes with modelling clay except for one small part at the bottom. This represents a cave mouth or spring. You can decorate your hill with rocks, grass, trees and flowers if you wish.
Note: I purchased modelling clay and when we opened it, it was all dry and crumbly. I took it back and this is the only packet they had left to replace what I had purchased, so we didn’t have a choice of colours.
We added a few rocks around our little opening which you can see on the photo above (the yellow modelling clay).
Use the toothpick to poke a couple of holes in the top of your clay hill. It would have worked better if our holes were closer to the wall of the container, but oh well. These holes let the water drip slowly into your cave.
We filled up a 600ml water bottle and used it to slowly pour the water over the top of our clay hill. It will take a while, but the water will slowly filter down through the holes into the cubes of sugar and eventually out of your spring or cave at the back.
After a bit of a wait, you should be able to see the sugar cubes start to erode and then watch the clay sink slowly due to having supporting rocks. This is when the sinkhole forms.