The original crater is thought to have been created about 142.5 million years ago by an asteroid or comet, and at the time was about 22km in diameter. This has since been eroded away leaving the current 5km diameter crater like feature that you will find yourself standing inside of at GZ.
The impact of the meteor would have sent up a mushroom cloud, not too different to that of an nuclear bomb, and whilst the size of the meteor has never been determined, it has been established that at the time of impact it was travelling at 70km/second. The energy generated is estimated to be about 200000 times greater than the Hiroshima atomic bomb.
The site is also known as Tnorala, and is a site of sacred significance to the Wester Arrente Aboriginal people. As you make your way around the crater site you will see the dream time stories of these people.
The evidence of the impact of a comet was first explored in the 1960's when a large abundance of shatter cones were discovered.
Shatter cones (cone-shaped fractures in rocks produced through extreme shock) are known to be very rare geological features that are only known to form beneath the impact site of craters or underground nuclear explosions.
As the name suggests the shapes of the rocks are conical, but can also be more of a spoon shape at the larger end of the cone. Shapes of Shatter Cones can vary in formation depending on the type of rock. For example in limestone there tends to be a horsetail pattern with thin grooves, whereas coarser rocks tend to have less defined patterns and grooves.
Sizes of shatter cones can range from microscopic right up to several meters in size, with the largest known one being more than 10m in length.
Access to the Reserve is presently by road via Hermannsburg to the south or Tylers Pass to the north. Both roads are recommended 4WD only, but we observed many 2wd cars in the area during our visit, with the majority of these of the hired variety.
Upon arriving at GZ there are picnic tables, shelters, and a long drop toilter. Note that there is no running water available, and the nearest service town is Hermansberg.
Whilst the area is not a long drive from Alice Springs visitors should be prepared for the area that they are in, and adequate food and water should be carried at all times, even during the winter months, and even more importantly during the summer months.
To log this cache you are asked to answer the following questions by reading the information provided at or around the listed GZ.
1. In the structure of the surface how many thousand layers are exposed that would normally be below ground.
2. By how many years ago had erosion and a wet climate reduced the centre of Australia to a flat plain?
3. How far below the land surface were rocks subjected to compression and shock waves?
Please send your answers in an e-mail to us via our GC profile (don't post the answers in your log!). If you feel like it feel free to post a photo from the lookout nearby to GZ. Please also tell of funny stories like we experienced when at GZ, such as being asked where the crater is, despite having driven inside it, and looked around!
Again, whilst this is only a day trip from Alice Springs you should be prepared and ensure that you have adequate water.
Information sourced from austhrutime, NT parks & wild life, and Wikipedia.