Sculpted by Nature EarthCache
Hidden : 10/12/2014
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

Smile

Rooivalle Falls is one of the most beautiful spots within the Karoo National Park. Take the scenic drive along the picturesque Klipspringer Pass with its environmentally friendly style of construction to the Rooivalle Falls viewpoint. The name is derived from the fact that the water turns red after rains. Over 20 breeding pairs of Black Eagles find sanctuary within the park. One of these pairs has made Rooivalle their home.

Smile
Flat topped hills (called Karoo Koppies) are highly characteristic of the southern and southwestern Karoo landscape. These hills are capped by hard, erosion resistant dolerite sills. This is solidified lava that was forced under high pressure between the horizontal strata of the sedimentary rocks that make up most of the Karoo’s geology. This occurred about 180 million years ago, when huge volumes of lava were extruded over most of Southern Africa and adjoining regions of Gondwana, both on the surface and deep below the surface between the sedimentary strata. Since this massive extrusion of lava, Southern Africa has undergone a prolonged period of erosion exposing the older softer rocks, except where they were protected by a cap of dolerite.

The Karoo Supergroup of Permian age consists of the Dwyka Formation, Ecca Group and Beaufort Group.

The Beaufort group overlies the Ecca group and consists of alternating mudstone (red in places) and sandstone. It sub-divides into the lower Abrahamskraal Formation (1 500m-2 000m thick) and an upper Teekloof formation (±1400m thick) with the boumdary arbitrarily at the base of the so-called “Poortjie Sandstone”.

This formation consists of mudstone (red in places), sandstone and thin greenish cherty beds. The sandstones represent river channel deposits and the mudstones, floodplain deposits. The cherty beds were originally ashfall tuffs, although the presence micro-cross-lamination suggests subsequent transportation by water onto the floodplains. Jurassic-age dolerite extensively intrudes the Beaufort Group as dykes and sheets. Inclined sheets form crescentshaped or concentric intrusions that are clearly visible on the Middle- and Upper Plateau.

The sills range from a few metres to over 100m in thickness. The dolerite causes a metamorphosis effect on the adjacent host rocks. Mudstone altered to hornfells and the sandstones develop a quartzitic appearance. Deposits of Quaternary age include river terrace gravel, calcrete, alluvium and debris. Terrace gravel consists of fairly well-rounded cobbles and boulders composed largely of dolerite. The terrace gravel shows clearly along the banks of the Gamka River where sharp profiles occur.

These gravels are partly calcrete cemented and occur on terrace remnants that now lie from a few metres to a maximum of 30m above the general land surface. Calcrete occurs directly on bedrock and has also formed extensive deposits within some larger areas of alluvium, attaining a maximum thickness of a few metres. The alluvium embraces both alluvial slopes (sheet wash) and alluvial valley (channel-related) deposits, with the former predominating in the Lammertjiesleegte and the latter dominating in the Stolshoek areas of Karoo NP.

Vegetation types are closely linked to soil type, soil depth, rockiness, slope and aspect. Finer soil types with smaller grains (such as clay) generally retain moisture better than coarse-grained soils. In soils with very high clay content water may be retained so well that it is unavailable for absorption by plant roots. Clay also forms a compacted surface more easily, causing water to run off rather than penetrate deeply into the soil. Deep soil, if it is too sandy does not retain water as well as rocky soils. Vegetation growing on rocky soils is therefore more resilient to the effects of drought and grazing. Deep Karoo soils are very easily eroded by wind and water if denuded of a healthy vegetation layer, leading to even more degraded veld with poor fodder production for herbivores.

Soils

The dominant soil-forming processes have been rock weathering, the formation of orthic topsoil horizons and, commonly, clay alleviation, giving rise typically to lithucutanic horizons. Soil forms that are typical of these processes are Glenrosa and Mispah. Any other soil form can however also be found in these land types. Oakleaf soil forms, deep or shallow, developed by rock weathering also occur in upland sites.

The steep slopes, middle plateau and Puttersvlei (upper plateau) areas of Karoo NP, excluding the northern most corner, fall into the Ib land type. Surface rock with underlying soil or rock covers sixty to eighty percent of these areas. The parent material of the slopes consists of mudstone, siltstone and sandstone with some dolerite intrusions, and typically Mispah or Glenrosa soil forms. Dolerite covers most of the middle plateau, with an influence of mudstone, siltstone and sandstone closer to the upper slopes.

Fertile soils occur on this flat plateau with little erosion save where the deep red soils gradually erode from a natural basin. Dolerite rocks cover most of the Puttersvlei section of land type Ib, with the underlying sandstone appearing in terraces, descending in a northerly direction. The northernmost corner of the upper plateau occurs in land type Db. Prismacutanic and/or pedocutanic diagnostic horizons characteristically dominate this land type. Non-red B horizon, duplex soils cover more than half the land area.


Now on to the Earth Cache.


You are permitted to get out your car and got to Ground Zero. (this is the view point.) Remember there are wild animals in the park, including Rhino and Lions so do this at your own risk.

To log this Earth cache you will need to answer the following questions.

1: At Ground Zero what are you standing on. Name the type of Rock or Soil.

2: What is the main colour of the Rock or Soil and what do you think makes it this colour and describe its look.

3: How was the above made / formed ?

4: From Ground Zero you will see a good example of "Karoo Koppies " Flat topped hills. Describe how these "Karoo Koppies " came to be.

5: There is a sign, road side close to the view point. What is the warning on this sign.

Keep a eye out for The Black Eagle, Ground Zero is a good place to spot them.
Remember to email your answers to Familybehrens007@gmail.com - or via my Geocaching profile page
Please Do Not post any Spoiler pictures.


References: http://en.wikipedia.org/wiki/Karoo_Supergroup, http://en.wikipedia.org/wiki/Karoo, http://www.sanparks.co.za/parks/karoo/conservation/ff/geology.php, http://en.wikipedia.org/wiki/Karoo_National_Park

Additional Hints (No hints available.)



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