Cave Formation, Guilin
Are you interested in limestone cave formation?
Your China travel to Guilin will certain cover cave tours. In my experience, Chinese tour guides seldom cover the topic of cave formation which some travellers could be of interest. I have therefore researched the topic and summarized some facts about how limestone caves are formed.
Please note that the photos on this page are samples only. They are not taken from any of the Guilin caves.
Pre-requisite - Limestone Landscape
Guilin is the only place within China that has beautiful limestone mountains together with peaceful rivers. All these set a perfect natural environment for cave formation.
The Creation of a Cave
Cave formation begins when rainwater absorbs carbon dioxide as it falls through the atmosphere. Rain water must have carbon dioxide to become acidic. It must be acidic to chemically react to the limestone bedrock. Rainwater is absorbed by the soil into the ground.
As rainwater comes through the soil it absorbs more carbon dioxide that is being produced by plants that are dead. This changes the ground water to a weaker form of carbonic acid (H2O + CO2 = H2CO3). As it travels down through the ground it comes to solid rock. When the rock is limestone or dolomite caves can form.
The water reacts chemically with limestone and slowly a larger and larger space will form. This happens because the rocks are made of calcium carbonate (CaCO3). This is what you call chemical erosion.
As the space becomes larger and larger the water can flow through. As it flows it erodes. Physical erosion washes away rock and sand. This is what makes a cave larger and forms an underground stream. Finally over hundreds of thousands of years or even millions of years the cave is formed.
Source of information: the 8th grade members of the Raymondville Stream Team as part of their water quality research.
Limestone Cave Features
• Stalactites - hang from the ceiling
• Stalagmites - grow from the ground
• Columns - when a stalactite and a stalagmite meet
• Gypsum flowers, hair, needles - form in dryer caves
• Temperature in a cave is the average yearly temperature in that area
• Caves are almost 100% humid
During your Guilin travel, please check if you could find above features in the caves.
I have a little tip to help you remember the two terms stalactites and stalagmites. Just associate ‘c’ with ‘ceiling’ and ‘g’ with ‘ground, then you would never forget which is which.
How Fast do Stalactites and Stalagmites Grow?
Stalactites grow according to the conditions that prevail where they are formed. Some may take thousands of years to grow an inch whereas others may grow an inch in six months.
Research over the past five years in the Kelly Caves of Kangaroo Island (South Australia) has shown that stalactites can grow at rates of up to 1/2 inch (7mm) in four years.
What about Guilin? Your Guilin travel might not provide you with an answer. However it is believed that the cave formation at Reed Flute Cave started 600,000 years ago. I am still researching on how long the Crown Cave has taken to form. If you have any idea, please drop me an
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