A Class on Geology

This semester I had one first year class in geology. I can't quite remember why I chose to take it, partially it looked interesting and partially as I was taking a related second year course I thought I might be required to take it.

Anyway most of the material seems to contain examples from Canada or America. Many times we have gone through powerpoints of rock types across Canada, talked about the Burgess Shale Fossils in the Rockies, or looked at a map showing the danger zones in BC, specifically in case of "The Big-One" (ie earthquake) happening near Vancouver. In many cases my friends in the class have asked me if I've been there, live near there or if the pictures remind me of home! Sometimes I do think of home, but I'm surprised by how strongly Canadian geology plays a role in education here. If anything I feel a stronger connection and deeper respect for my lovely country!

I think the leading factor that decides where the material comes from is due to the fact that the textbooks are often printed or written in the US or Canada. However we do tie in some Australian geology to the lessons, which makes the class more unique from if I'd taken it at home.

This past week, we had a trip down to lower Sandy Bay for the practical and I learned some new, and scary things about the place I was living.

To start with we were shown three small peaks across the river which actually were made by volcanoes during the Tertiary. The most recent still has a conical shape while the other two are much more rounded. Tasmania and the rest of Australia are not volcanic now but in the past they have been influenced by volcanic activity, probably due to passing over a hot spot at they shifted north.

Tasmania has also had it's share of land slips and slides, which people tend to forget. The iconic casino/hotel built in 1973, became Australia's first after a positive referendum was held in Tasmania. When the city's engineers were looking for a place to build it, they decided on the flat land found in lower Sandy Bay. The design was approved for 25 stories and work began. Unfortunately for them, they should have done a proper analysis of the land before. They had chosen to build the casino on a section of land that had been flattened when part of Mount Nelson crumbled and slid towards the Derwent river. The center of the casino was also to be built on top of a fault! All of this was common knowledge to the geology department at UTAS, who had done quite a bit of research on this area. But with construction already starting, some new designs to account for the unconsolidated rock beneath were needed and the casino was reduced to 17 stories with the games rooms set up around the tower.

The Casino is more than just a recognizable tower at night!

That's not the only time city engineers should have payed more attention to the geology. The lovely Tasman bridge also has a rocky, or should I say rockless past. When it was time to replace the floating bridge that connected the Eastern Shore with downtown Hobart, two options were thrown around. The idea of a suspension bridge would have been a wise one. On either side of the river (rifted open as Tasmania was pulled to stay behind with Antarctica or head north with the rest of Australia) there is excellent bedrock very old in age. This would have been great for the beams of support required by a suspension bridge. However it was decided that a beam bridge would be a better choice. Images of the river bottom in the chosen area were a bit confusing, but it was assumed that it was just sediment rich and rock was somewhere beneath. They started building on the Eastern shore and discovered that the rock beneath was actually not as old as thought. However it was still good bedrock and work continued. Close to the Western shore, they dropped the pylons expecting to hit rock...however they kept on going. They rock had ended and they had reached mud! This stopped construction for a while, but the engineers managed to design a branching end that would keep the western beams stable in the mud. Construction finished allowing the bridge to be opened. However, in the case of a nearby earthquake, all that unconsolidated mud may flow out, collapsing the bridge! Scary stuff!

Bridging more than just two sides!

Thus I've learnt quite a bit about local Tasmanian geology, which makes me wonder what hidden treasures (disasters) we might have waiting for us at home?