Kunjarra (The Pebbles) 

An Earthcache by Seemyshell

The History

Kunjarra/The Pebbles is an outcrop of mysterious granite boulders located 11 kilometres north of Tennant Creek. Known to the Warumungu Aboriginal people as Kunjarra, The Pebbles, known as the smaller relatives of the Karlu/Karlu /Devils Marbles. Here, dancing and healing rites of the Munga Munga dreaming take place.

Location: North of Tennant Creek. Access is just past the Telegraph Station for those travelling north on the Stuart Highway, and there is six kilometres of unsealed road, access is suitable for all vehicles, I rode in on my large Motorcycle.

When: Time your visit for sunset to witness the changing colours of the granite stone, from glowing red and orange, through to deeper purple and grey as the sun disappears behind the horizon. Free camping is also permitted at the location, it has bathroom factilites, and fire pits. Please be respectful and take all rubbish with you.

The EarthCache

(As with all Earthcaches there is no physical container to find, however you will learn some geology of the area)

The Pebbles are small granitic rocks that form the exposed top layer of an extensive and mostly underground granite formation. The natural processes of weathering and erosion have created the various shapes of the rocks. 

The Pebbles are a smaller version of the nearby Devils Marbles as they constitute a degraded nubbin. The formation is made of granite and are part of the top layer of a formation which penetrates the ground from below, like little geological islands in the desert, surrounded by large amounts of sandstone. The granite was formed millions of years ago as a result of the hardening of magma within the Earth's crust. Thick layers of sandstone on top of the granite exerted extreme downward pressure on the granite. After some time, tectonic forces caused folding of the Earth's crust in the area, which lifted the granite and fractured the sandstone, allowing the granite to come closer to the surface. As the pressure diminished, the granite expanded causing cracks to form, and then the larger formations began to separate into big, square blocks.

The next phase of the formation of the Marbles started when the blocks were exposed to water. The surface of the blocks began to decay under the influence of the water and a layer of loose material surrounded the individual blocks. When the blocks came to the surface completely, the loose material was eroded away by water and wind.

The rounding of the granite blocks is a result of chemical and physical weathering. Chemical processes cause the surface of the blocks to expand and contract, resulting in thin layers of rock coming off the boulder in a process called exfoliation. This process rounds the granite block because the chemical processes have more effect on areas with edges. The rock begins to look like it is made of layers like an onion. Only the outer few centimetres are affected by chemical weathering in a process called spheroidal weathering.

The boulders are affected more deeply by the extreme temperature differences between day and night in the arid desert region where the reserve is located. During daylight hours the rocks expand slightly and after nightfall they contract slightly, repeating the process every 24 hours.

To claim this earthcache, you will need to answer the following questions located at the site, along with some of your own thoughts on The Pebbles. You will need to message me with these answers, however no need to wait for a responce to log your find.

Go to WP2. Here you will be able to touch and feel the pebbles.  

1. What rock are the 'Pebbles' made from?

2. What do the Pebbles feel like, describe their texture.

3. In your opinion, why do they have that texture?

4. Post a photo with you ar GPS at the location. (Sunset or Sunrise is amazing)