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.
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.
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.
Cradle Mountain 
Scrambling up 
Cradle Mountain 
Barn Bluff 
From the summit
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!
Furnaeux Geotrail Markers 
This huge boulder is in the paddock across the road from Mt Strzelecki. It obviously rolled down from the top! 
Near the peak of Mt Strzelecki 
Castle Rock 
From Yellow Beach 
Basalt rocks strewn across Petrifaction Bay
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.
Big 
Bigger 
Biggest! 
The Geotrail signs are supplemented by a QR code with more detail.
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
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.
From Highfields Historic Homestead. 
The Nut – Stanley 
View from the top.
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.
Strata with shell fossils 
Fossil Bluff 
obvious layers AND fossils – what more can you ask for!
