Aries Tor, located within Kosciuszko National Park in New South Wales, Australia, is a striking rock formation that captivates hikers, photographers, nature enthusiasts and now hopefully, geocachers.
A ‘tor’ is a prominent rock or pile of rocks, usually found on the top or side of a hill.
Kosciuszko Region Geology: During the Ordovician period (approximately 450 million years ago), the area around Mount Kosciuszko was submerged under an immense sea. Over time, sediments from this ancient marine environment transformed into metamorphic rocks, including slates, phyllites, quartzites, and schists. Some of these rocks are still visible today between Rawson Pass and Watson’s Crags.
During the Silurian and Devonian periods, the region experienced folding and uplift. About 390 million years ago, magma intruded into this metamorphic rock, cooling to form granite batholiths. A gradual erosion of the upper rock layers followed, with only the most resistant rocks remaining, giving rise to peaks like Mount Kosciuszko. Approximately 65 million years ago, Eastern Australia experienced significant uplift, raising the Snowy Mountains to their current elevation.
Glaciation occurred about two million years ago, resulting in successive moraines, cirques, erratic blocks, and glacial lakes. The carving action of these glaciers shaped much of the landscape of the Snowy Mountains.
Tor formation: The joints or fractures in the granite that ultimately form the tors occur through three distinct mechanisms.
Firstly, the hot magma intrusion slowly cools to form a granite batholith. A batholith is a large intrusion of igneous rock that forms from cooled magma deep in Earth's crust.
As the magma cools, it shrinks and contracts, with the resultant shrinkage stresses causing fracture joints. These are usually oriented vertically. The spacing of these joints in tors is related to the rate of cooling of the granite. Larger tors are attributed to slower cooling where there has been less stress in the cooling rock as it shrinks resulting in wider spaced joints.
Over time, the rocks covering the granite intrusion erode, exposing the granite batholith
Secondly, as the rock overlying the batholith erodes, there is less weight and pressure bearing on the batholith, which expand. This expansion causes stresses in the rock and creates mostly horizontal fractures in the process (since the rock expands upwards). The orientation of the fracture joints typically follows the shape of the surrounding land. For instance, these joints are usually horizontal on an exposed hilltop and inclined on valleyside tors.
Thirdly, water seeps into the fractures in the rock. When this water freezes it expands. This creates significant mechanical force, further prying open and fracturing the granite. As melting ice thaws, it carries away any loose material. This freeze and thaw process is repeated over millions of years, until the granite is split into blocks.
The size and shape of the resulting granite blocks is influenced by the spacing and pattern of the fractures. Where there are more fractures, the blocks may be completely broken up and in time, will erode away quicker than surrounding blocks.
Once the granite blocks are exposed, spheroidal weathering of the squared joint blocks rounds the corners of the blocks.
Logging this Earthcache: To log this earthcache, you must visit Aries Tor and answer the following questions:
- Describe the rock (colour, texture and grain) at Aries Tor. What type of rock is this ?
- Consider the vertical jointing of Aries Tor. What is the approximate spacing of these vertical joints? To the south nearby (about 70m) is a much larger exposed rock formation. Compare the joint spacing of this rock formation with Aries Tor. What can you deduce about the relative cooling speed of the magma intrusion at both locations?
- Consider the horizontal rock joints of Aries Tor. Are they perfectly horizontal or tilted slightly? Describe their orientation with respect to the surrounding landscape. What does this tell you about the topography of the surrounding landscape millions of years ago when the covering rocks eroded and these joints formed?
- Take a photo of yourself with your GPS or geocaching name visible with Aries Tor and the mirror pool in the background. If you are shy then take a photo of a personal item showing your geocaching name with Aries Tor in the background instead. You must post this photo with your found log (mandatory).
Answers should be sent via the geocaching message or email systems. Feel free to log your find when you have sent your answers. Don't forget to include your photo with your found log. I will contact you if there are any issues with your answers or if your photo is missing.
There are lots of other interesting granite tors in Kosciuszko National Park. I have listed two coordinates for interesting tors near Rams Head North and Mt Townsend.
I would love to see your photos of any other interesting tors you discover with your log.
Getting There: The easiest route is to make your way to Thredbo Village, then catch the Kosciuszko Express chairlift from Valley Terminal to the top of Thredbo Ski resort. At the top, follow the Kosciuszko Walk towards Mount Kosciuszko.
An alternate route is to start at Charlotte Pass and walk along the Summit Walk towards Rawson Pass. At Rawson Pass, follow Kosciuszko Walk back towards Thredbo. During the summer months you can also ride a bike from Charlotte Pass to Rawsons Pass and walk the remainder.
There is no formed path from the Kosciuszko Walk steel boardwalk to Aries Tor. At your chosen location, you will need to venture off the boardwalk, and climb the hill and into the bowl shaped valley on the other side where Aries Tor can be found at the foot of the valley.
Fees: There are fees applicable for entry to the Park.
Leave no trace : Leave only footprints and take only photos. The cache is located in a National Park, which is protected by law. All applicable rules and regulations must be complied with at all times. Follow minimal impact bushwalking principles. Please make the effort to collect and carry out any rubbish you come across. I would love to see some photos of your CITO efforts with your found logs.
Staying Safe: Please check for and take heed of all alerts on the Kosciuszko National Park web page before setting out.
Weather conditions can change rapidly, and snowfalls and blizzards can occur at any time of the year. Please take the usual precautions for a hike of this nature, practise minimal impact bushwalking and stay safe.
Mobile phone coverage cannot necessarily be relied upon. Ensure a reliable friend or relative knows your plans before setting out. You should pack a PLB, first aid kit, food and water, appropriate layers of warm clothes and wet weather gear. UV radiation is extreme in alpine areas. Protect your skin from sunburn by using sunscreen, and wearing sunglasses, protective clothing and a hat.
This cache involves venturing off track. You need to be proficient in off track navigation and always carry a GPS and appropriate maps and a compass.
References
- https://www.meteorologiaenred.com/monte-kosciuszko.html
- https://www.jstor.org/stable/10.2307/1790301?searchText=&searchUri=&ab_segments=&searchKey=&refreqid=fastly-default%3Addf6b7cefa4ca2baede13e8a8d8a6233
- https://www.dartmoor.gov.uk/__data/assets/pdf_file/0025/72097/lab-tors.pdf
- https://en.wikipedia.org/wiki/Tor_(rock_formation
- https://www.vedantu.com/geography/tors
- https://en.wikipedia.org/wiki/Batholith