Pildappa Rock

At Minnipa we turned north off the Eyre Highway and travelled about 15 km to Pildappa Rock. It's south of the Gawler Range and different altogether geologically speaking.

The wave at Pildappa Rock

The rock is an inselberg of pink granite formed about 7 km below the surface and exposed by erosion. It's most attractive feature is the wave and there are numerous gnamma rockholes on the top of the rock, many holding water when we visited. Some had vegetation and one had tadpoles.

Pildappa Rock and Gawler Range in the background.

Mosses, lichens and succulents on the rock.

Flowering vegetation in one of the rockholes (and a butterfly wing).

Tadpoles in a rockhole.

Vegetation in a rockhole

Pildappa Rock was a delightful place to visit.

Anakie Gorge

Folded rocks in Anakie Gorge

To walk back in time you only need to walk a short distance from the Picnic Ground at Anakie Gorge.

The Brisbane Ranges plateau was once, about 500 million years ago, submerged under an inland sea and the layers of sediment deposited on the seabed eventually compacted into slate and sandstone. The area became exposed over the years and under pressure about a million years ago the land east of  the Rowsley Fault that extends from about Bacchus Marsh to Geelong began to sink (Port Phillip Sunkland). The result was an impressive escarpment. Rivers like Little River and StonyCreek eroded deep valleys through the escarpment as they moved down to what is now Port Phillip Bay. Today we can clearly see the layers of ancient rock in the Anakie Gorge formed by Stony Creek.

And, as a bonus, I can promise numbers of birds all year round and a wildflower display in spring.

Harman's Valley and Mt Napier

Mt Napier erupted over several decades about 8000 years ago. The lava flowed into valleys and over the landscape forming a shield around the volcano itself. Scientists can date the lava flow that filled Harman's Valley with carbon 14 isotopes of the peat that formed in a swamp after the lava filled a valley. 

Harman's Valley can be easily seen from a lookout on the road near Byaduk. And there are excellent information boards there as well. How else would I have known about isotopes!!

Lava blisters

It looked very different 8000 years ago. The local Aboriginals would have seen the lava slowly filling the valleys and spreading over the landscape in waves through several decades of eruption. 

We now call the volcano Mt Napier (more about that in the next blog) but I went to see the blisters, the tumuli, that form on the surface of a lava flow when gases build up beneath the surface. The dome roof collapses and the sides remain. The blisters (on private property along Old Crusher Road) are excellent examples apparently and much bigger than I expected..

There are no information boards at the site but at the Harman's Valley site nearby there are several that explain everything very well. The tumuli site is not far off the main road but the signposts do not entice the tourists so it can be very easily go unnoticed.

Geology

Minutes and hours are insignificant in the landscape around Alice. Here you have to think in years, millions of years. The rocks speak of eons. The geology is breathtaking in its beauty and so are the many plants we have found flowering.

A track winding back

The geology underlying our farm at Homerton is quite interesting. We have limestone under the sandy loam topsoil, a pretty strong clue to the fact that this area was under the sea in recent geological history. And we have sink holes all over the property, areas that have subsided when a limestone cave underneath collapses. Swamps and drainage lines on the surface follow a linear direction to the south-east, resulting in 'waves' in places. You can see this in the photo of a lane that runs alongside our property. When I was five I had to ride my bike to school on a road like this. It has since been levelled and sealed, and the one-teacher school has closed. That's progress I suppose.