The Victorian Twelve Apostles Landform
Hi fellow Physical Geography peers, I have today to share a good visit into what is known as one of Victoria's most prominent geological features that have shaped alot of our modern culture existing close to where I live. Now whether you may have alot of background on the history of the Twelve Apostles or not, I will leave you at least by the end of this post with something to think about it and hopefully enjoy the type of place as I did. This aptly named place is situated immediately south off the coast from the Port Campbell National park. This chain of large rock columns left out of the limestone cliff face of the headland near the Park is the marvel it became because of the process of the continual erosion of each column segment and the possible formation by the cracks in the wall of the headlands over so many millennia it is almost treated as divine sentinels as to which they gave it a strong sounding number for the name, even though the wave action decomposed in the same way the rocks broke apart from the headland. The name is still soundly regarded by people even though up until the nine that remained by the 21st century. One more collapsed by 2008 and so there are only eight Apostles left standing with a rubble of rock reef where the ninth one stood.
Now as I had taken the time to arrive there, I was partly concerned and intrigued about how it had taken the trip the long duration of upwards of 6 hours or so to get there but having stopped at various points of indulgement, or sightseeing such as Lorne and Apollo Bay on the trip, I would say I was glad to have done so - even if a direct trip to the apostles could have taken just 3 to 4 hours :). I went to do the enlightening work for you readers to find out about this magnificent place's location and best travel directions. As I found with mapping and GPS the main cluster of Rock columns are situated almost halfway from Princetown and Port Campbell the minor towns close to the feature and best accessible, which are connected by the Great Ocean Road but the Apostles are on the ground beach off the Great Ocean Road headland. It takes approximately a 280 kilometre drive from the Melbourne CBD along Princes Freeway, Princes Highway then off the Princes Highway southwards past Princetown Road, to where Booringa Road meets the Great Ocean Road, with a Bird Flies distance of about 190 kilometres.
The approximate distance of the same meeting area of the start of the sight from Princetown is about 2.1 kilometres along the Great Ocean Road (Google Earth measurement).
The official Victorian given Geographic GPS co-ordinates of the Twelve Apostles feature is latitude of 38.66293° S and longitude of 143.10576° E.1
Now looking at the few apostles that I could see from the main visitor area and platforms, with the rest of the remaining 8 hidden behind the transversely fluctuating headland sections along the Great Ocean Road Coast2, and that the ninth apostle recorded to have collapsed by 2005 July 3 3, I can be sure to believe and marvel at how great the ocean waves have worn down the unconsolidated rock with high damage over short periods.
This collection of limestone rock stacks out from the Port Campbell National park headland consists of large separated limestone columns that can reach up to a height of 45 metres elevation with about 1-3 dozen metres in radius as sedimentary landforms.
Most days' effect of light's ebb and flow constantly wash the colours of the rocks, changing anew and repainting the mysticity of the rocks and the Shipwreck Coast with time. Soaring over the horizon at dawn, the sun casts its wings of golden light to speck the land of roses and reds. Under a full sun as per the noon, the rocks would shine a blazing sandy yellow from the sun's true candle. As dusk arrives the falling sun explodes the sky with burn orange and lavender hues, bleeding onto the rocks as well eventually with the apostles draped in rainbow magic. The rocks finally transform into dark byzantine shades of umber and ominous ebony splashes into the dark night.4
The rocks were known as the Sow and Piglets, the Muttonbird island near Loch Ard Gorge being the sow, until 1922 to be renamed the Twelve Apostles for tourism and world recognition.
These Apostle stacks come from what is known as a gradational process, because of the weathering of the cliff and physical movement of earth material above the surface. And for such 'trophies' these rocks are, they are erosional landforms where they are the result of the limestone cliff weathering away. This is caused mostly by wave quarrying which is hydraulic action of water thrown against the cliff face. There is also some wave abrasion, caused by corrasive action by pebbles and sand against the cliff.
The Southern Ocean that meets the Port Campbell headlands bring very harsh and savage weather effects that gradually and slowly over years erode soft limestone to form caves in the cliffs, which continue to punch through the headland to reveal arches, which in turn collapse leaving the rock stacks standing on the beach.
These apostles stand along a beach, which is depositional since the waves transport load of mud, sand and stones dragged by swash and back wash mostly by offshore drift. This involves wave attrition when boulders and pebbles are smashed against the shore are themselves broken up and shape the beach.
The erosive weathering includes mechanical weathering by crystal growth from the waves soaking into the cliff which expand and leaves crystals of salts and dissolve into the rock because of the cracks formed by the strong delivery of waves into the cliff, its jagged outline created by various parts of the limestone cliff along the coast being softer than others, so the cliff face along the coast continually erodes and possibly leave more rocks detached in the future. The crystals will cause parts of the rock to split open the cracks wider and break down.
From most observations of the change in cracks of the limestone cliff and stacks it can be estimated that about 2-3 cm of rock wall would be eroded per year so it suggests it is better to be a visitor to see the place as earlier as possible from the modern day.5
The chemical weathering affecting the rocks involves hydrolysis, weakening and changing the rock from the waves crashing with the mentioned softer parts of the limestone. Sea spray, rain as well as wind and water carrying abrasive sand and gravel also have affected the rocks in such way. This easily undercuts the stacks and is compounded on the waves by the natural high moisture environment of the beach, they will eventually collapse and leave behind some regolith in reef or low platforms.
One of the larger stacks that are out there, named as 'London Bridge' once (now London Arch), facing especially more weathering and erosion even up to present, has undergone rapid coastal change. It used to be made of two arches attached to a headland attached to the Port Campbell National Park. By 1990 the arch on the near side to the land collapsed leaving the lone bridge like rock to be counted as one of today's apostles.6
Thinking back again to how these apostles appear to be now, I would believe to a theoretical extent that the factors to them forming at that location,
- When the exposed cracks from erosion are compounded by having the waves carry dissolving agents such as salt and more water and detriment is brought to the limestone cliff and rocks via precipitation, soaking into it as indirect runoff, this makes the cracks more and more weaker until they expand and become larger and larger to form the caves and arches, that allows for rock to break away from the headlands and so be the very apostles that stand
- Part of this weakening of the limestone headlands also affected in a similar but nearby action which as I mentioned is exemplified by the undercutting of the stone near the base sections, because those are weaker and frequently pounded on by the wave force, wave quarrying, which is the major effect in starting to form the caves, and bring down the past few collapsed apostles
- And as these caves form, all the broken, dropped material is weaker limestone, that contained sediments with mudstone and chalky clays would have been removed, but the stronger limestone that people can still see and its weight being held up because the fact that the non-siliclastic limestone (majority of Calcium Carbonate) can withstand more gradation than siliclastic stone such as Sandstone
- Over ten to twelve million years ago the husked skeletons of marine organisms and micro-organisms like molluscs, bryozoans and brachiopods collected and deposited on the sea floor. This material when amounted to thick beds and layers, solidified together to form masses of limestone rock, that eventually surfaced to meet air by the end of the Miocene period (5 million years ago) and that is when weathering and erosion hit the limestone cliffs, and form caves.6
- That's about the possible physical ways these rock stacks could have been formed, while if one wants to look at the theological and any superficial aspects that is another topic for review some other day.
For a set of large mighty rocks that could be described as formed from Miocene time (23 million years - 5 million years ago) because of the existing group of sea life types that actually melded to produce so much volume of limestone, I had an adventurous visit into such landforms, and believe that I may look forward to visiting the Apostles again in the future.
As visible evidently, the different layers can be observed to prove these are sedimentary rocks, while they have cracks weakened by weathering. Rain detriment combined with the salt crystals carried from the waves at the base, will in some time in future collapse this apostle into another wave cut platform.
Strong pounding waves moved by Antarctic winds buffet the bases of the Great Ocean Road limestone cliff and base of the apostles, which is enough to undercut the rock and create wave cut notches which will eventually make the rock give way or at the cliffs, create some caves.
Gallery
References
Cauchi, S 2005, 'Apostles face unstable future', The Age, 5 July, <http://www.theage.com.au/articles/2005/07/04/1120329384274.html>
Tourism Victoria, 12 Apostles Great Ocean Road Victoria Australia, <http://www.visitvictoria.com/Regions/Great-Ocean-Road/Things-to-do/Nature-and-wildlife/Beaches-and-coastlines/12-Apostles.aspx>
1 Port Campbell Visitor Information Centre, 12 Apostles Naming and location, Port Campbell Visitor Information Centre, <http://visit12apostles.com.au/natural-wonders/apostles-naming/>
2 Daily Photos & Frugal Travel Tips 2007, The Twelve Apostles Sign, Daily Photos & Frugal Travel Tips, <http://freephotooftheday.com/2007/03/18/the-twelve-apostles-sign/>
3 Great Ocean Road Regional Tourism Limited 2015, TWELVE APOSTLES, Visit Great Ocean Road, <http://www.visitgreatoceanroad.org.au/twelve-apostles>
4 Sightseeing Tours Australia 2014, History of the 12 Apostles, Sightseeing Tours AU, <http://greatoceanroadmelbournetours.com.au/blog/44-history-of-the-12-apostles>
5 Aaron & Janet <arjo4pedal@hotmail.com> 2006, 'Australia - December 17,2005 - February 21, 2006', web log article, 1 January, Earth By Tandem (Aaron & Janet), <http://www.earthbytandem.com/Australia.htm>
6 Lech, M. E. & Trewin, C. L. 2013, 'Weathering and erosion – some examples' in Weathering, erosion, landforms and regolith: Teacher Notes and Student Activities, 2nd edn, Record 2013/16, Geoscience Australia, Geoscience Austalia Education Centre, Canberra, ACT, Austalia, <http://www.ga.gov.au/corporate_data/75055/Rec2013_016.pdf>
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