karst landscapes

Threlkeldia diffusa growing in limestone

Karst landscapes develop when there’s limestone near the surface and lots of groundwater movement. Perth has both. Over time underground water works on the soluble limestone to excavate caves and sinkholes. Yanchep National Park has limestone caves and I grew up playing in the “pirate” caves at Trigg Beach.

I got all excited when my neighbour told me there’s a sink hole outside my house. Turns out me or my house won’t be moving to the Underworld just yet.

This weekend the electricity poles outside my house were replaced. It was meant to happen weeks ago but Western Power was having trouble with something in the ground. My neighbour told me the workers found a sink hole next to where they wanted to put the power pole.

earth works contractors plugging the exit to the Underworld

Yesterday morning earth works contractors were busy doing something out there and I asked for an update on my sinkhole. He dashed my hopes of underground exploration when he said its more likely a fracture in the bedrock. They were filling the fracture with soil, but first had to drill down and pump out water (above). Then they dropped a steel rod for the earthline of the power pole. Western Power had previously tried dropping the steel rod and it just kept going, hence why they thought there was a sinkhole.

So my house won’t be sinking anytime soon. I’ve always wanted to live underground, although I’m not sure whether I’d prefer an underground house or a limestone cave, probably both.


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