Karst Mountains
Guangxi province is acclaimed for its limestone pinnacles and spires. As you survey this fairy-tale landscape, you might wonder how it came to be.
Development of cone and tower karst scenery
“Karst” describes the effect of underground water on massive blocks of soluble limestone. It takes place where there is well-jointed limestone near the earth’s surface, a moderate to heavy rainfall and good groundwater circulation. Rainwater, acidified by carbon dioxide in the air and by plant debris in the soil, percolates along horizontal and vertical fractures in the limestone, dissolving it and carrying it away in solution. This process, over time, forms conduits and then channels, which in turn accelerate the rock’s erosion. In Guangxi province, this process has produced deep rugged gorges along the limestone’s joints and fractures, dividing its original mass into isolated blocks.
When intervening blocks are rounded into closely spaced conical hills this formation is known as “cone karst”. In other places, the deepening gorges, having reached a base level, have begun to widen. This has created a lowerlevel plain from which the remnants of the original limestone block stand out as isolated, near vertical towers – this development is known as “tower karst”.
The special touches like private lunches at the base of the limestone mountains in Guilin, to the private bamboo river rafting were spectacular. We will all remember these moments for the rest of our lives!S.G., USA
Principle Features
Since karst depends upon the movement of subsurface water, its predominant features, other than the superficial cones and towers themselves, concern subsurface water movement. Here are some features to look out for:
- Cave – previously a water passage; now an air-filled, underground void.
- Losing stream – one whose bed allows water to flow directly into the groundwater system; hence it disappears.
- Natural bridges or tunnels – a short void, beneath bedrock, allowing human passage from one end to the other.
- Sinkholes – these occur when the roof of a cave collapses. You may see a sheer vertical opening into a cave, or a shallow depression that can extend for many acres.
- Spring – a natural resurgence of ground water, which usually occurs along a hillside or valley floor.
