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This Earthcache is located in Kruger National Park at the Hippo Pools. Please note: You may not alight from your vehicle at this site! The ranger who used to work here has retired, so you can no longer leave your vehicle at this location. All answers can be found from the safety of your vehicle, so there is no need to put yourself in danger due to the resident hippos, lions, and crocs.
Welcome to the Hippo Pools! This site, located on the Crocodile River near the Crocodile Bridge Gate at the southeast end of Kruger National Park, is often one of the first views that a visitor will have of flowing water within the park. Access is by way of Road S27 off of the Crocodile River Road (S25), a few kilometers west of Crocodile Bridge Gate.
As you arrive and park your vehicle in the car-park, note the sandstone outcrop on your left. The sandstone at this site has begun forming cavities or hollows called tafoni. This process is also called honeycomb weathering or cavernous weathering, and the structures called “wind holes”. Though not well understood, this is thought to occur mainly through a form of wind and water erosion.
In one hypothesis of how tafoni are created, moisture through the form of dew or precipitation enters these rocks and dissolves some of the harder minerals. These are leached to the surface, where the water evaporates leaving a coating or crust on the parent material. Some time later a piece of this outer crust breaks or weathers off and wind erosion begins to eat away at the softer material below. The rock eventually weathers to the form which you see here.
Tafoni is usually found to be associated with crystalline sedimentary rocks, such as sandstones.
Further along the sandstone wall, there is an example of San rock art. Animals thought to be Elands were carved into the rock. Proving that this is still a dynamic system, floods in the year 2000 destroyed much of the existing artwork when rocks were washed away from this part of the river.
To log this Earthcache, send me an email with the answers to the following questions, remembering to stay in your vehicle as you acquire the answers:
1.) Estimate the average size of the cavities formed in the sandstone.
2.) Are the cavities the same size, or many different sizes? Why do you think this might be so?
Please consider posting photos of yourself, or the local geology, when you log this EarthCache. Photos can be an additional rewarding part of your journey, but posting them is not a requirement for logging this EarthCache, and is strictly optional.
The above information was compiled from the following sources:
2007. Hilton-Barber, B. and L.R. Berger. The Prime Origins Guide to Exploring Kruger, 2nd Edition.
Kruger National Code of Conduct. Found online at: (visit link)
2008. South African National Parks Visitors Guide: Kruger National Park.
Tafoni: (visit link)
Thanks to the SANParks, and Kruger National Park, for allowing placement of this EarthCache!
(No hints available.)