The Pilanesberg ring dike complex, as seen by the Landsat 8 satellite's camera. Photo by NASA/EO
MAHIKENG, South Africa, July 22 (UPI) -- South Africa is home to many natural wonders, but perhaps its least appreciated is the nation's alkaline ring dike complex in Pilanesberg National Park -- the largest and most well preserved in the world.
In June, the camera on Landsat 8 -- one of NASA's many Earth-observing satellites -- captured a magnificent view of the geologic phenomenon.
A ring dike complex is an intrusive rock formation, like a dike or sill, but with a massive ring-like pattern that reveals the volcanic nature of its ancient subterranean source.
Different types of protruding igneous, born of the plumbing of an ancient underground volcano, form a ring of ridges and valleys stretching roughly 15 miles across. Most of the hills rise somewhere between 500 and 1,000 feet above the surrounding lowlands, while the highest peak tops out at 5,118 feet above sea level.
The formation formed over several million years beginning some 1.3 billion years ago. Waves of volcanic activity pushed up rock formations, with eruptions scarring the landscape and magma cooling as it settled back into the fissures in the caldera's crags. Magma from the central chamber rose up through cracks, forming protrusions.
Eventually, eruptions cause the volcano to collapse in on itself. The increased pressure forced even more magma to the surface, cooling to form new dike formations in gaps and cracks. Each new protrusion formed a unique type of igneous as different types of magma cooled under a variety of conditions.
"White foyaite has particularly coarse grains and is formed when lava cools slowly," NASA explained in a recent press release. "Red syenite forms when magma contains plenty of water. In the detail image, outcrops of white and green foyaite and of red syenite make up the ridges in the southwestern part of the park."
Because these rocks are especially resilient, they've become more dramatically exposed as surrounding rocks are weathered away by erosive forces.