We generally think of mountains as tall, broad ridges–a sort of wall of stone. Rocky structures aren’t often found as distinct entities, with a small base and a narrow, steep-sided body. Occasionally, such promontories stick up above the surrounding lands, like Devil’s Tower or the sandstone pinnacles of Monument Valley, but these are solitary, or few in number, and catch our attention for their shape and isolation. There is a region in China, however, where a vast amount of land is covered with tall, pointy, natural stone structures ranging from cone to tower shapes. You have no doubt seen artistic renderings of them in old Chinese screen prints and may have thought they were fanciful landscapes dreamed up by the painter. As otherworldly as they appear, the southern provinces of Guangxi and Guizhou have abundant vistas filled with such natural wonders, especially near the city of Guilin and the area of Yangshuo.
To see these spires of stone is to wonder, how did they come to be? Why aren’t there lots more places like this? The ingredient that makes the whole landscape possible is limestone. This area of southern China was once a sea basin, filling in over time with the calcareous remains of sea creatures and sediment. Eventually, it was buried deep enough to press it all into stone, thousands of meters thick. Subsequent uplift brought this rock deposit above sea level, and fractured the enormous limestone body, forming what is called karst topography. The copious rainfall in these areas, sitting in and just north of the tropics, provides a steady source of limestone-dissolving fluid. As raindrops fall, carbon dioxide in the air interacts with water to form a weak carbonic acid. Nature has nothing but time, so the cracks in the rock eventually become gullies, and streams slowly dissolve out caverns and cave systems with underground drainages. Under the right conditions, such a landscape can produce more than underground features—in southern China and a few other select areas, it has created narrow pointed peaks ranging from 100 to 1,000 feet in height.
Western geomorphologists group the kind of tall, pointy structures found in karst areas as either cones or towers depending upon their shape. The Chinese use a nomenclature that involves the formation process of these structures, and the surrounding landscape. The type they call fengcong is mostly represented by cone-shaped peaks, situated in clusters. The depressions between and amongst the peaks, called dolines, result from both surface dissolution, and the collapse of caverns at depth. The valleys between the peaks are not continuous, so there are no surface-flowing rivers in them. Drainage goes on underground, cutting more caves and caverns. As tectonic forces keep lifting the landscape, the rivers cut deeper, the low areas continue collapsing, and the peaks get relatively higher.
The Chinese category called fenglin karst, on the other hand, is typified by more vertically sided towers, with wide, flat areas between them, often the site of agriculture, mainly rice paddies. In these fenglin areas, rivers flow on the surface and cut away at the bases of the cones, steepening their sides into towers as uplift raises the whole area. This explanation is quite simplified, but the process of producing the cones and especially the towers is quite complex, and a large number of factors are in play. Moreover, these forces of erosion, deposition, surface collapse, chemical interaction, geologic uplift, etc, must all coordinate in their timing to get the fantastic results of the Guilin area. It is also key that this location is void of a history of glaciation. Glaciers tend to mow down the heights of a karst region. All this is why the Guilin spectacle is so rare. The precise interplay of so many processes over a very long period is a very unlikely occurrence.
The Chinese are justifiably proud of these natural wonders and promote the Guilin area to travellers, who have marveled at the sights there for centuries. Taking a boat down the Li River as it winds through the mystical spires is an awe-inspiring trip. Increased tourism due to China’s improved economy and greater openness to the outside world has brought crowds and some tackiness to the nearby urban areas, but the experience of the tall peaks is still something special. We are lucky to be living in this particular time in geologic history, as eons ago the place was just a fairly featureless limestone plain, and eons from now all the fantastic shapes and the great limestone layer will be finally dissolved and worn away. Makes you wonder what other mind-boggling artifacts of Mother Nature’s handiwork were produced and ground down millions of years ago, that no human ever laid eyes on. Enjoy this one now!
The fabulous karst formations of southeast China are a geologic wonder to behold, but you can see all the topography of China with this stunning satellite image wall map, available from Maps.com.
caption: Chinese art has depicted the strange and enchanting karst formations for centuries.
source: Wikimedia Commons: www.seattlecentral.org (Public domain)
caption: Fengcong, or cone karst, makes for multi-peaked mountains along the Lijiang River.
source: Flickr: Rex Pe (CC by 2.0)
caption: Fenglin, or tower karst, leaves solitary sentinels standing on a flat plain.
source: Wikimedia Commons: G41m8 (CC by SA 4.0 International)
caption: Many tour the karst areas by boat cruise.
source: Flickr: David Boté Estrada (CC by SA 2.0)
caption: The limestone spires make a mystical backdrop.
source: Flickr: Grey World (CC by 2.0)
caption: The landscape of the Guilin area is almost unbelievable.
source: Flickr: 2il org (CC by 2.0)