AA lists the walk to see the Rob Roy Glacier as number 52 on the 101 Must-Do’s for the Queenstown region. The AA website describes the valley as follows: “Imagine a vista so beautiful it takes your breath away – a glacier hanging high above a flowering alpine meadow with waterfalls and icefalls cascading down to the valley below while above the soaring peak of Rob Roy rises high into the deep blue sky.”
The Rob Roy Glacier is a cirque glacier. Cirque Glaciers are small ice masses, wide in relation to their length, which exist in small armchair-shaped hollows. Although they often possess large terminal moraines, they lie in a true rock basin. They may be separate ice masses or simply the head of a valley glacier as shown in the figure below.
Glacial landscape by Surachit
According to Embleton, Glaciation is generally accepted as one of the primary factors in cirque formation. Glaciation includes three processes: sapping, corrasion and transport. The term sapping implies frost-riving on the rock slopes under the margins of a glacier. It is produced by the freezing of any water which flows in under the ‘cold’ glacier and in the case of cirques, it results in a horizontal retreat of the headwall. Corrasion includes the process of abrasion and plucking of a glacier’s bed and is produced by the glacier’s movement. Flow phenomena agree in general with the phenomena of rotational sliding, namely a forward and downward motion at the head (névé), a forward and upward heaving at the toe (tongue), and a sliding along an arcuate basal surface with little deformation of the moving mass as shown in the figure below. The flow action is primarily in a vertical sense; that is, it tends mainly to deepen a cirque.
Flow of a cirque glacier. The arrows indicate the particle motion.
Transport, the third process of glaciations, involves the removal of eroded debris. It is important in that its clearing away of debris offers continuously fresh working surfaces to the processes of sapping and corrasion.
According to Hambrey, backward erosion by three or more cirque glaciers in combination with frost-shattering, may lead to the intersection of the cirque headwalls. This can result in the isolation an upstanding mass of rock called a horn. A horn represents the stage at which all of the original, smooth highland has been eroded. A famous example of a horn is the Matterhorn which has three nearly symmetrical ridges rise steeply towards a pyramidal summit, each face carrying a steep cirque glacier. Other well proportioned horns are Mt Assinboine in Canada, Mt. Aspiring and K2 in Pakistan. Most horns, however, lack this symmetry owing to the uneven backward erosion of cirques.
Rob Roy Track
Logging this EarthCache requires that you following the Rob Roy Glacier Walk to the listed coordinates. The walk begins at the Raspberry Flat car park which is about a 1 hr drive outside of Wanaka on mostly dirt roads. From the car park, follow the well marked trail for approximately 15 minutes until you come to the swing bridge across the West Matukituki River (coordinates listed). At the swing bridge, you will be required to write down some of the details on the information board. Once across the swing bridge, the track climbs through a small gorge into beech forests. The trail is steep and rocky at first as shown in the photos below.
However, soon, the trail continues along a well maintained trail which continues upward at a small incline.
Eventually, the trail leaves the river and rises up to a meadow where you will find good views of the glacier. The meadow is a great place for a picnic but beware of the Keas which frequent the area.
The walk to the listed coordinates from the car park is 10km. Plan accordingly and expect to need about 5 hours return. You can find the brochure for the the track on the Department of Conservation website.
Be sure to check weather and road conditions with the Mount Aspiring National Park Visitor Centre prior to starting the drive to the Raspberry Flat car park. The road to the car park crosses several fords which can be deep if it has been raining. Furthermore, the weather in this area can be unpredictable and alpine conditions can arrive at any time of year. Please check the Department of Conservation website for tips on how to prepare for the tramp.
To log this EarthCache, you must complete the following:
1. At S 44° 30.370 E 168° 43.602 which is the start of the swing bridge, there once was an information sign and you were asked a question about the sign. However, until the sign is replaced, you no longer need to answer question 1.
2. Record the altitude at the listed coordinates: S 44° 28.698 E 168° 43.688. Note the altitude is not the same as that given on the information display.
3. Provide the names of at least four horns caused by cirque glaciers.
4. Describe the three processes that formed the cirque.
5. Take a photo of your GPS with the Rob Roy Glacier clearly in the background. Feel free to be in the photo as well, but only the GPS and glacier are required. Post the photo with your log.
Please email all of the answers to the cache owner prior to logging your find.
The following books were referenced for this description of this EarthCache:
Embleton, C., Glaciers and Glacial Erosion, Macmillan, London, 1972.
Gerrard, J., Mountain Environments : An Examination of the Physical Geography of Mountains, 1st MIT Press Edn, MIT Press, Cambridge, Mass., 1990.
Hambrey, M. J., Glacial Environments, UCL Press, London, 1994.
Menzies, J., Modern Glacial Environments : Processes, Dynamics, and Sediments, Butterworth-Heinemann, Boston, 1995.
The figures and photos with the exception of the glacier landscape are by looking4thebroc.
The flow of a cirque glacier figure by looking4thebroc is based on Embleton.
The glacial landscape figure by Surachit is public domain.