00:00We're looking into State Circle and we can see this long road cutting here.
00:06It's a stunning road cutting that shows the relationship between two very important geological units of the Canberra District.
00:16And the relationship between the two is what's known as an unconformity, which is a break in the geological record.
00:23But these rocks tell us the story of the Canberra District about 420, 430 million years ago.
00:33That's in the Silurian period when this area was under the ocean.
00:38It was actually the early Pacific Ocean that extended over here.
00:42And the nearest land was further west near Broken Hill.
00:46Now, although we can see it today and it looks quite spectacular,
00:49there was a time when this was going to be covered in concrete and or landscaped.
00:54Is that right?
00:55Yeah, the original plans for this cutting was not to enable us to see the rocks that we love today.
01:01In fact, the original plan was to either landscape, so plant with different shrubs,
01:08or to even concrete the cutting.
01:11And the local geological community made a lot of noise about how sad it would be
01:17to lose not only a fantastic looking exposure of rock,
01:22but scientifically really important for understanding the different bits of the jigsaw puzzle
01:28of Canberra's environmental history.
01:30It's almost better than artwork, is it?
01:32I think it is.
01:33And I love it.
01:34You've got rocks that are different colours because they've weathered differently.
01:38They've got faults through them, so there's blocks that are moving around,
01:42and they've all been folded as well.
01:44So, yeah, there's a lot to put your eyes across when you look at this cutting.
01:47And in fact, be careful when you're driving,
01:50especially if you're driving behind a geologist,
01:52because you might find the car starts wandering.
01:55Talking about geologists visiting here,
01:57is this a popular site for geology students and or, you know,
02:01international geologists that might come to Canberra or Australia for conferences or field trips?
02:07Is this a hot spot for them?
02:09Yeah, in fact, the whole Canberra district has some of the best Silurian geology in the world.
02:14So people come from around the world to see it.
02:16And this cutting is one of the great geological exposures of the Canberra district.
02:22So we get lots of geologists visiting.
02:25It's also a fantastic training locality for university students and high school students
02:32to come and understand rocks and how they fall.
02:35And it's just by coincidence that it happens to be between old and new parliament house,
02:40two prominent Australian buildings.
02:42Yeah, it's an amazing window into the hill, Capitol Hill, and what lies beneath it.
02:48And once you see this, you then start looking around at all the other hills in the district
02:52and it makes you ask questions about, wow, I wonder what lies beneath them.
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