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Canberra’s geological roots are reflected in many of its place names, and conversely many of its rocks reflect the local geography in their names.
The view in the photograph is of Black Mountain taken from Mount Ainslie.
Both promontories are the product of geological processes dating back to the Silurian Period.
Black Mountain is formed of “Black Mountain sandstone” sitting atop “State Circle Shale”.
These rocks were laid down around 435 million years ago, when underwater avalanches (turbidites) raced off an ancient continent to the depths of a Silurian ocean.
Our view of them is from Mount Ainslie, formed of the “Ainslie volcanics” – about 425 million years old, these are ignimbrites –
sub-aerial avalanches this time, of burning hot ash and pumice erupted from Silurian volcanoes set in the shallow seas of the (then) continent’s margin.

So, happy birthday Canberra, and as you celebrate 100 years of civic and federal fun, raise a glass of local Riesling (one of the best!) and remember your ancient roots.