Hiking Chiang Mai’s “Sticky Falls” — How This Rare Natural Wonder Got Its Super SpiderMan Power

One of the best waterfall excursions you can take in Chiang Mai is to a rare (and free!) natural wonder about an hour north-northeast of the city, Namtok Bua Tong น้ำตกบัวตอง,  better known as “Sticky Falls” (inexplicably, Buatong is actually a Thai name for a type of sunflower). The spring-fed falls earned the moniker “sticky” for the amazing spiderman-like traction you can get climbing up their steep (about 50 degree) submerged slope without slipping. I will briefly explain the science behind the magic below, but first, here are a few pictures of a hike getting to the sticky falls the long way!

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18 km One-Way Hike 

This hike took some transportation coordination with a hired red truck driver, as it started about 18 km from the falls at the “Pan Din Wit” แผ่นดินหวิด viewpoint. 

Below is the route straight to the falls, if you prefer not to do the one-way hike.

The hike included an easily accessible cave about 4 km in (there are small wooden signs to look for), and though long, was fairly level with a pleasant forested down-sloping trail along a stream with “hidden” waterfalls near the destination.

Why are the Sticky Falls Sticky?

The short answer is because calcium carbonate precipitates out from the spring water and sticks to the surface. That crystalline substance has a porous molecular structure that makes it less slippery, even when wet. But to give the full story of how this wondrous compound came to be in a mountainous waterfall in Chiang Mai, we need to start around 450 million years ago! 

To give perspective on these long time scales, and help with some of the illustrations below that refer to geological ages, here’s a handy chart from Encyclopedia Britannica. The bottom starts at 650 million years ago, up to the present at the top.

Between 600 to 530 million years ago, much of the earth’s landmass was consolidated in the supercontinent Gondwana.  As part of the general breakup of that formation, a section split off from the tectonic plate containing Australia. Geological scientists call this piece of crust the Shan-Thai, or Sibumasu, Terrane. (Terrane—not to be confused with terrain– means a mass of earth’s crust that has broken off of one tectonic plate and become attached to crust lying on another plate).

That bit of crust became an archipelago in an ancient sea called the Paleotethys. As the terrain drifted northward through hundreds of millions of years to eventually join the Indochina and Sukhothai Terranes (to the east) and South Chine Terrane (to the north), it was often inundated by the seas, when ages of marine life—mostly tiny shells made of lime (calcium carbonate, CaCO3)–accumulated. Over eons of compacting, these fossilized shells, along with mud, became limestone.

Starting about 100 million years ago, the Indian subcontinent began a race from south to north, to come crashing into the Eurasian continent. The violence of this slow-moving but powerful impact formed the Himalayas, and also twisted and uplifted the Shan-Thai terrane to form the mountain structure we see in today’s Thailand. You can view a computer graphic of this collision here (the video starts from present to 100 million years ago, then reverses back to present):

The geology of the Chiang Mai area is quite complex as a result of the collision and compression of numerous tectonic plates or terranes. Mainland Southeast Asia is a collage of terrane blocks originating from Gondwana and volcanic arcs separated by narrow zones called “suture zones”. 

Chiang Mai’s surrounding area is composed of three terrane blocks–the Shan-Thai, also called Sibumasu (on which the city and environs of Chiang Mai sit); Sukhothai; and Indochina. When you’re hiking in Northern Thailand, it’s easy to imagine the collision of these massive blocks forming the north-south oriented ripples of mountains to the east and west of the Chiang Mai basin. 

The area around Sticky Falls lies close to the “Chiang Mai-Chiang Rai Suture Zone”, which is the boundary between the Sibumasu and Sukhothai terranes. 

Sibumasu Terrane slides under the Sukhothai terrane along the Mae Tha fault. The illustration below shows the subduction (sliding under) of the Shan-Thai/Sibumasu Terrane and explains that there are several theories as to what is happening at the surface.

With the confluence of so many geological zones, the area contains numerous “faults”, which means a fracture or zone of fractures between two blocks of rock that often can slide over or under each other. This exposes many different types of formations, such as limestone blocks and other rocks that were once under the Paelotethys ocean, rich in carbon deposits from ancient life. Although Sticky Falls is just off the map to the north, the illustration below shows the numerous fault lines that pepper the region.

The Bio-Chemistry of Stickiness

Accumulation of limestone or other carbonate-rich formations explains the source of calcium carbonate in the spring water that feeds Sticky Falls. 

The technical term for the structure of the falls is “tufa”. Tufa is a “secondary” form of limestone, because it usually comes from a primary limestone formation dissolving in acidic rainwater and then reconstituting when it re-emerges from the ground enriched with carbonates. As seen in the illustration below, the rainwater with carbon dioxide seeps into the ground, and is slightly acidic. The carbonate minerals in the ground dissolve in this acidic solution, saturating the groundwater. That saturated and ambient temperature (same temperature as the surrounding environment) water emerges at the spring called Namphu Jet Si (น้ำพุเจ็ดสี), literally “Seven-colored Spring”. 

Several special conditions are required for tufa formation, and the tufa can vary in appearance and character depending on these conditions. One condition is difference in pressure. When the springwater emerges into the atmosphere, it is under less pressure than when the water is undergound.  Sunlight and biological organisms also play a part in forming the carbonate structure of tufa. Finally, in the particular case of Sticky Falls, which can be classified as a “cascade” formation, the fast flow and aeration of the water plays a role. All these factors combine to cause Carbon Dioxide (CO2) to release from the water, with the result that the calcium carbonate precipitates (becomes a solid) to form the porous, slightly flexible structure known as tufa. The basic chemical equation looks like this:

Ca2+ + 2 HCO3-↔ CaCO3 + CO2 + H2O. 

The Ca is Calcium, which comes from the biological material. The HCO3 is Bicarbonate, or Hydrogen Carbonate. The carbon also comes, at least partly, from the biological material. The CaCO3 is Calcium Carbonate, which provides the basic structure of the tufa. The H2O, of course, is water.

The illustration below shows in microscopic detail another tufa formation in Guadalajara, Spain. The formation appears slightly different than sticky falls, but it’s easy to see the porous structure, and how it can allow feet to grip onto the surface, even under water. 

More Places to Put On Your Bucket List

From my research, the exact conditions to form tufa seem to be fairly rare. That makes the Buatong Sticky Falls a pretty special place! Although it’s somewhat far, I highly recommend making a trip to the falls if visiting Chiang Mai.

Other precious sites worth a visit for global travellers are the result of a similar process that forms Travertine. The conditions for travertine formation depend on hot springwater, rather than cool or ambient temperature water. Travertine formations are less porous and slicker than tufa, but they create incredibly beautiful places around the world–and make great building material!

Here are a few of the more spectacular places to see natural travertine formations:

Mammoth Hot Springs, Yellowstone National Park, Wyoming, USA

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Badab-e Surt, Manzandaran Province, Iran

Huanglong, Sichuan Province, China

Hierve el Agua, Oaxaca, Mexico

Semuc Champey, Guatemala

Pamukkale, Denizli Province, Turkey

So many natural wonders, so little time! Let’s pack our bags and get started!