Geology Part 2 – Stories from the Great Southern Road Trip

Road sign saying Geology Point

Geology Nerd – Part 2 – Tasmania

This post is the second of a two part series about some of the geology and geological formations I encountered on my recent road trip across the south-east of Australia. Part 1 included those features seen in NSW. After scooting through Victoria as quick as I could because of concerns related to a five day COVID lock down I boarded the Spirit of Tasmania with my trusty Suby and all my camping gear.

Once off the ferry, it didn’t take long before I started to see some interesting things rock-wise. The descriptions are listed in the order I visited them.

Do rivers count as geology?

The first thing to catch my eye while driving from Devonport to Launceston was the Rubicon River. I’m not really sure if riverine vegetation counts as geology but what the heck! The islands of grass made sinuous patterns in the slow-flowing water. After a little investigation, it seems that these clumps of grass are in fact an invasive species called rice grass. There is a federally funded program to help eradicate it.

Geology - Islands of grass in the Rubicon River Tasmania
Rubicon River – Islands of Grass.

Bakers Beach – Narawantapu National Park

My first glimpse of Tasmania’s famous orange boulders was on a grey day. A fine mist of drizzle was fogging up my lens. The rocks are orange because they are clothed in red-orange fuzz formed by the symbiotic relationship between lichen and fungi. The boulders are granite and their smooth rounded shapes are easy to scramble over. There were orange rocks at almost every beach I visited. The shape and size of the boulders and the size of their crystals varied a lot but the colours remained fairly consistent.

Orange granit boulders next to blue water
Bakers Beach my first glimpse of the ubiquitous orange rocks of Tassie.

Cradle Mountain National Park

While there are no glaciers in Australia these days there is plenty of evidence of their existence in the Cradle Mountain National Park. This area is spectacular, with large outcrops of granite-like dolerite. The craggy, jagged peaks make excellent photographic subjects and the area is one of the busiest tourist destinations in Tasmania. There are lots of walks in the area from short strolls to the arduous 6 day Overland Track. If you are not up for this long walk there is a 13 km Cradle Mountain Summit Walk.

The solid geology of Cradle Mountain has been described by many! This snippet is from a detailed report by I R Jennings. I could not find a date for the actual publication but the date on a map says November 1958. If you’d like more detail it’s an easy read despite the length.

Simple… realy

Barn Bluff, although looking very much like a volcanic plug is the result of extensive weathering of the dolerite intrusions.

Geology Bonanza! Flinders Island

What a treat Flinders Island is! A feast of geology and all on a very small plate as it were. I spent four days on Flinders and I am so glad I did. There is a geotrail! Imagine me doing a merry little dance and clapping my hands when I saw the first sign! I really recommend having a look at the website before you visit. Also, see my previous post about my visit.

Choose from red lichen coated rocks, massive boulders in the middle of paddocks, a summit climb, pegmatites and more! There’s topaz for those who like to fossick, plenty of sandy beaches and shallow coastal lagoons. Sigh!

The thing that got me really excited were the pegmatites (really really big crystals) at Killecrankie on the northern end of the island. How big? BIG! For reference, I included an Australian 50 cent coin that has a diameter of 31 mm. Super big crystals of course mean super slow cooling of the molten lava below the surface.

Marakoopa and King Solomon Caves – Mole Creek

The Mole Creek Karst Conservation Area has hundreds of caves. Some are open to the general public and others are open only to experienced spelunkers. When you book they tell you to dress warmly and you should! The caves stay at a steady 9oC throughout the year. I did a tour of both Marakoopa and King Solomon Caves. Marakoopa has an underground creek and glow worms while King Solomon’s Cave has larger caverns. “Discovered” by Europeans in the mid-1800s it has been a popular tourist destination ever since. The cave tours are led by interesting guides. Due to COVID restrictions, the numbers were very low which, in my opinion, enhanced the experience. You’ll need a camera with an adjustable ISO because flash photography is not permitted.

Alum Cliffs

Always on the look out for a good walk, long or short – I stopped to check out Alum Cliffs. It’s included in Tasmania’s 60 best short walks. It is only a 1.6 km return walk. At the end of the wooded path you suddenly come out to a platform which is perched 200 m above the Mersey River below. Take care if you suffer from vertigo.

Tulampanga, the Aboriginal name for Alum Cliffs, remains ​a place of particular significance to Aborigines because of the ochre found nearby. Along the walk there are sculptures and pieces of outdoor furniture, some created by local Aboriginal artists. 

https://parks.tas.gov.au/things-to-do/60-great-short-walks/alum-cliffs
Alum Cliffs

The Nut – Stanley

The Nut, an ancient volcanic plug, dominates the town of Stanley. You can climb or drive to the top or if you’re a bit braver, ride the chair lift. Chair lifts freak me out a bit! Generally, I am not scared of heights per se, but chairs lifts… shiver…..There is a 2.4 km loop walk up the top which gives you great views of the town below.

Fossil Bluff – Wynyard

And finally fossils! Plenty of them too! Fossil Bluff is on the western side of Wynyard which is in north west Tasmania. So much of geology to see here! Layers of marine fossils, boulders and a rocky beach.

Bit of wind noise sorry…

Geology Part 1 – Stories from the Great Southern Road Trip

Road sign saying Geology Point

Confessed Geology Nerd!

I’m a rock nerd! I have more than a passing interest in geology and geological formations. Given that I’m a high school science teacher I feel that interest is very legitimate! While my knowledge is rudimentary, (my degree was mostly chemistry) I know enough to be able to read the stories held in rocks. Although it’s more like the abridged Readers’ Digest version, the outline is there! I know the difference between igneous, sedimentary and metamorphic rocks but can’t identify many by name. My recent Great Southern Road Trip gave me lots of opportunities to check out some interesting scenery. 

Geology and Geotourism is an increasingly popular way to travel and Geotrails are becoming more common.  I have a great map called the Geotourism Map of NSW but I have not found one for the other states. It gives locations and details of some of the interesting formations.

This post shows some of the features I snapped along my way down the NSW coast and then in Tasmania. I missed plenty! I will just have to go back on another road trip – darn. I will give the broad brush strokes of what took my interest rather than a detailed explanation of the geology or geological history. (If you’re a geologist I’m happy to have your input in the comments below!)

Originally, I was planning on covering the geology encountered in both NSW and Tassie in this one post but it’s getting too long so I’ve split it into a two-parter.

Far South Coast of NSW

Jervis Bay – Moe’s Rock and surrounds

I don’t know who Moe was but the rock platforms in this area look bubbly and aerated. More likely there is some differential weathering of the sandstone. The colour of the sandstone also varies significantly. The lumpy, almost pillowy surface adds a lot of interest. While you are here in Booderee National Park have a look at the Cape St George Lighthouse. For the pedantic, Jervis Bay is actually not part of NSW but is governed by the ACT. In addition to whiter than white beaches there is a large-ish naval base there.

Bateman’s Bay – Denham’s Beach.

At the north end of Denham’s Beach there are two interesting features. Firstly the nicely folded rock wall and secondly the large potato like rocks strewn over the rock platform. When I first came across them, I really thought they were potatoes. Smooth, round and light coloured. Some have a coating of green algae. The rock wall has several very distinct strata. At the base is the dark rock which also makes up the platform. It is overlaid with lighter rock with embedded darker stripes.

Eden – South End of Aslings Beach

At the south end of Aslings Beach there is a magnificently striated and folded rock wall. At the base, there is a man-made rock pool. The layers are multi-coloured and in the right light glow with a rich red hue. These two photos taken at different times of the day and from a different angle and show off the folds and erosion.

Light to Light Walk – Green Cape National Park

You can walk from Boyd’s Tower to Green Cape Lighthouse. It is a 33 km walk and typically done over two days. Along the way there are LOTS on interesting features. The colour of the rocks is spectacular especially in contrast to the green-blue ocean. If you don’t want to do the walk, you can still access some of the spots via road. I did parts of the Light to Light Walk and have written about it in another post.

Australia’s Highest Peak – Mt Kosciuszko,

A COVID lockdown in Victoria meant I needed to change my plans (quickly!!!) and head west. I climbed to the top of Mt Kosciuszko on a fine sunny day via the Main Range Loop Track. I have written a separate post about the walk. The landscape is dominated by large granite tors. You can read about how tors form on Wikipedia.

The Rock – near Wagga Wagga

Maybe a little more thought could have gone into the name for this particular landform? The Rock juts out from the landscape very dramatically and is about 30 km south-west of Wagga Wagga. There is a walking trail to the summit, which according to the NSW National Parks and Wildlife Service, is a 6 km return walk. At this stage of my road trip I was a tight schedule to get to Melbourne to board the Spirit of Tasmania, so whizzed past without stopping! (Except to pull over to take the photo!!)

The Rock from the Olympic Highway

Part 2 – Tasmania

Check out my next post showcasing the geology and some of the geological features in Tasmania. Coming soon!