The Abel mountains of Tasmania
Intro: There is something special about mountains when you are a geologist (i.e. a person who spends a good chunk of the time thinking about rocks). Their prominent peaks seem to allure and beg to be reached. Growing up in Canada I’m used to being surrounded by gorgeous glacier-caped mountain. Sadly, these are missing in Australia. However, here in Tasmania there are heaps of stunning little mountains that fill the gap; and they are mostly all within reach with a short drive out of Hobart and a day or twos’ hike. In fact, there is a whole book on these mountains compiled by an avid Tasmanian bushwalker, Wilkinson (1994). These mountains are called “The Abels” (named after the discovered of Tasmania, Abel Tasman) and are a list of the highest mountains in Tasmania (i.e. over 1100 m with over 150 m vertical drop on all faces).
The reason some of the most elite Abels look so impressive is due to a combination of the rocks they are composed of, and the glaciers that scraped, shaped and carved them! I recently took it on myself to try and summit some of these, and this post is about their most common geological formation, highlighted on one of the most regarded Abels in the wild southwest of Tasmania; Mt. Anne.
Science Spiel: Peak Exposure (Glacial Geomorphology, Geology)
Mt. Anne is located in southwest Tasmania, nestled within the wilderness near Lake Pedder. At 1423 m it protrudes sharply from the surrounding bush-land. The peak is made of the famous rock type of Tasmania; dolerite. When the dolerite intruded the land in the Jurassic (~ 180 Ma) it cooled rapidly, leading to the characteristic columnar joints observed in many localities in Tasmania (e.g. Cape Raoul and Maria Island). Most of the highest peaks in Tasmania are comprised of these dolerite columns, but only at a few localities, like Mt. Anne, you can see the contact to the older Precambrian basement rocks like quartzite (a common rock-type that comprises another famous Abel I hiked last year).
During the last glacial maximum (i.e. ~ 20,000 years ago) cirque, valley and small ice cap glaciers developed on the mountains of western and central Tasmania (Corbett et al., 2014). It is estimated that ~ 1085 km2 of ice covered the land. Cirques and valley glaciers accumulated on the leeward of mountain ranges, and some great examples of these can be seen around Mt. Anne, as well as near Frenchman’s Cap. Other glacier-derived features, like the sharp crescent moraines near Lake Judd by Mt. Anne, mark the limits of where the ice went.
To determine how long ago ice retreated, techniques like cosmogenic nuclide exposure-age dating using 10Be have been done of rocks within the glaciated regions of Tasmania (e.g. Barrows et al., 2002; Kiernan et al., 2004; Thrush, 2008). As Tasmania entered the present day cool temperature climate the ice melted and retreated, and while doing so, carved and exposed a large portion of the Abels seen today!
Final Thoughts: With over 160 Abels, and only a limited time in Tasmania (I am a full-time PhD student after all), I sadly do not think I will ever complete the list. However, it is fun to give it a go and I’ll keep trying to tick them off during my time in Tasmania. There is an unfortunate confession I have to make for this Mt. Anne trip… I camped the night on the plateau before the final summit to Mt. Anne in the morning, and then the fog and wind came overnight, making it unsafe for an ascent that morning!
Alast, this Abel will need to be properly summited again soon so I can tick it off my list! While the competition aspect is appealing, the true beauty of the Abels is an appreciation of the mountains and their surroundings. Their geological formation and late glaciated history are what truly make the Abels a wonderful little group of mountains to explore in Tasmania!
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