Mount Sonder marks one end of the Larapinta Trail, which extends 223km to Alice Springs. The shape of the mountain is a double peak, the relative heights of which are somewhat ambiguous from the summit, although easy to identify from the surrounding plains. The mountain can be seen for the western half of the Larapinta trail, up to Ormiston Pound, which obscures the mountain from then on.
A clearly defined walking track exists up the western side, taking about 12 kilometres. Water is available from a water tank 50 m beyond the carpark, and a direction plate can be found at the summit. This however is not the true summit, which is 750m away, but has been chosen for safety reasons. The view from the top boasts the taller Mount Zeil to the west, the West MacDonnell Range to the east, Glen Helen, a nearby resort, to the east and Gosses Bluff to the south west on a clear day.
Some 350-300 million years ago a mountain building event created the MacDonnell Ranges, of which Mount Sonder is included. This was known as the Alice Springs Orogeny. Since that time, folding, faulting and erosion have shaped the range and created numerous gaps and gorges. It is understood that both the gravity and teleseismic travel-time anomalies within the Arunta Block,created a thrust zone resulting in the mountain that you see today. These cliffs here are made up from heavitree quartzite, a very hard rock and it forms well defined upstanding ridges, resisting erosion better than the surrounding smaller layers of sediments laid down during geologic events. It's a quartz-rich sandstone with many grains cemented by quartz or partially re-crystalised to an interlocking crystal mass.
To successfully complete this earth cache, you need to answer the following questions:
1. What geological event created Mount Sonder?
2. When did this event occur?
3. What type of rock is Mount Sonder and the surrounding mountain ranges?
4. Are these rocks sedimentary, igneous or metamorphic?
5. Optional, take a photo of you in front of Mount Sonder and send with your answers.
Please do not write your answers in your log.