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!

Cruising the Gordon River Tasmania

Tree huggers win

The Gordon and Franklin Rivers have close to mythical status in Australia. They symbolise the start of the political party “the Greens” and intervention by our Federal Parliament into what had previously been considered State business. 

Back in the 1980’s the Tasmanian Government planned to dam the Franklin River for the purposes of hydroelectricity. A massive and effective protest movement arose with a strange alliance between old loggers and “tree-huggers” to protect the wild rivers. 

Eventually in 1983,  the newly elected Federal Labor Government led by Bob Hawke stopped the development and the area is now a UNESCO World Heritage protected area. 

The pristine, undeveloped and wild area cannot be easily accessed by vehicle and most areas remain undisturbed except by intrepid bush walkers. Several tour companies also run river cruises for the first 12 km of the river. They are required to travel at very low speeds in the river  to prevent bank-damaging wash. No commercial crusies are allowed beyond the 12 km mark. 

The area near Strahan had been selectively logged for the fabled Huon Pine since colonial settlement but now, no commercial activity other than boat cruises are allowed on the river.

World Heritage Cruises

As part of my Great Southern Road Trip, I booked a Premium seat (aka window seat) with World Heritage Cruises. The cruise leaves the jetty at Strahan at 9 AM and returns at approximately 3PM. Prices vary but I paid $165. In the height of summer (December and January) there is a second afternoon cruise. 

The cruise includes lunch. Normally a buffet, but in these times of COVID it was a prepackaged bento box with a bread roll, cold meats including smoked salmon, salad and cheese. Drinks and snacks can be purchased separately throughout the cruise. If you book a Gold ticket, morning tea is included.

The cruise takes you out of Macquarie Heads through “Hell’s Gates” a very narrow opening to the ocean, Sarah Island, an aquaculture area and the Gordon River. At the end you can also watch a traditional saw mill in action cutting up salvaged logs.  

You get off the catamaran at Sarah Island for a half hour walk around with a very entertaining guide from the Round Earth Company and you can also leave the boat at the 12 km turnaround point for a short board walk through the forest. 

There is extensive commentary from the boat’s captain and owner as well as some video clips displayed on monitors. This commentary was detailed and interesting. The Grining family who runs this particular cruise company have lived in the area for generations. Firstly as loggers, then loggers with a tourist side business and now the tourism business is their main activity. The family were also actively involved in the 1980 protests. The Grining family lobbied their passengers to sign a petition, ran supplies to the protesters as well as ‘smuggling’ in new protestors to the protest line.

Sarah Island

Sarah Island is a small island in Macquarie Harbour. It was a penal settlement for secondary offenders, that is convicts who reoffended. It was a “hell on earth” with harsh weather adding to the man-made deprivations and frequent floggings. Many of the convicts tried to escape. It’s history is bloody and it was closed after 12 years and the convicts moved to the equally infamous Port  Arthur. The history of Sarah Island is certainly worth checking out. 

As you can see it was raining heavily!

Poor weather

The Western coast of Tasmania is wild and the weather can be just as wild. At a latitude of 40o South the area is buffeted by the “roaring forties”. The next closest landmass in South America. It rains here frequently with the average annual rainfall being a little over 2 metres.

On the day of my booking it was raining heavily and cold. Visibility was poor but the sea was relatively calm. When we got out at Sarah Island, even though I had wet weather gear on, I still got soaked through. Cold I know is a relative thing. Cold here in Australia counts as anything less than about 15C! The previous day had been clear and 25C but on this day it maxed out at 15C.

One of the lighthouses at Hell’s Gate.

The boat

The Harbour Master 2 was only launched in 2020. It is an impressive double hulled aluminium catamaran. It has comfortable fittings and seats. It has large windows and open decks at the front and rear. There is a bar/cafe. As stated they usually serve a buffet but because of COVID restrictions still in play they served prepackaged Bento boxes.

Gold Tickets holders sit on the top deck and have access to the roof deck. When you are boarding and awaiting departure watch the time lapse video of the boat’s construction.


Despite the poor weather, it was still a good day out and I would recommend it. There are other tour companies which run similar trips. Gordon River Cruises also have a catamaran and Stormbreakers run an over night cruise in a sailing boat. I wish I had of seen this before I booked the other cruise!

Note: because of the poor weather and reduced visibility I don’t have many photos! I did make this tongue-in-cheek video of highlights.