TRAVELS, NATURE / CLIMATE
Feb 9, 2025
St. Beatus Caves and Traces of Time
"The underground caves hold records of climate and environmental changes dating back thousands of years."
All our daily experiences and the memories engraved in our minds are gained on the surface of the Earth. For this reason, life seems limited to the planet's surface for most of us. However, beneath our feet lies another world, where sunlight does not reach, and the howling of the wind is unheard.
In this world, underground waters have patiently carved rocks for millions of years, revealing some of nature’s most fascinating works. These caves are also natural archives that preserve the history of our planet and climate changes. In this article, I have compiled my notes from a visit to one of these archives, the St. Beatus Caves on the shores of Lake Thun in Switzerland.
A World Shaped by Underground Waters
According to legends, these caves are known as the place where the Irish monk St. Beatus took refuge after defeating a dragon in the 6th century. However, beyond religious or mythological narratives, the true mystery of the cave lies in its geological heritage, which spans millions of years.
This massive cave system was formed by underground waters slowly dissolving limestone rocks over millions of years. So far, approximately 14 kilometers of the cave have been explored, but only 1 kilometer is open to visitors. The cave’s interior temperature remains between 8-10°C throughout the year. If you visit during the summer, you may suddenly feel chilled, as if stepping into a refrigerator. This stable temperature also provides an ideal environment for the ongoing geochemical processes inside the cave.
Impressive Geological Formations
St. Beatus Caves were formed by the erosion of soluble rocks such as limestone by underground waters over thousands of years. The stalactites, stalagmites, and columns found in the cave were formed by mineral-rich water dripping and depositing minerals over millennia.
Stalactites: Calcite formations hanging from the ceiling, created by the accumulation of minerals carried by dripping water.
Stalagmites: Formations that grow upward on the cave floor as minerals accumulate from dripping water.
Columns: Vertical mineral formations that extend from floor to ceiling, formed when a stalactite and stalagmite merge. This process can take thousands or even millions of years. While there is no distinct column in the images I shared, there are a few candidates.
Inside the cave, mineral deposits of various colors and shapes can be observed. Although the formations in the shared images appear similar in color, their hues vary depending on the minerals they contain:
White → Pure calcite (CaCO₃)
Yellow & Brown → Iron oxides (Goethite - FeO(OH))
Red → Hematite (Fe₂O₃)
Black → Manganese oxides
Greenish & Bluish → Copper compounds
In temperate climate conditions, a stalagmite grows approximately 0.1 mm per year. At this rate, it would take around 10,000 years to reach a height of 1 meter. This means that a 1-meter-high stalagmite started forming approximately 10,000 years ago, aligning with the Neolithic Age—the period when agriculture and settled life began.
The Importance of Stalactites and Stalagmites in Paleoclimate Studies
Stalactites and stalagmites are among the most reliable sources for deciphering climate records spanning thousands of years. The process behind this can be summarized as follows:
The water droplets inside the cave originate from surface precipitation and infiltrate underground before reaching the cave.
As the precipitation filters through the soil, it absorbs carbon isotopes depending on the density and type of vegetation in the region.
The water from precipitation deposits new mineral layers on the stalagmites and stalactites in the cave.
Each new mineral layer preserves the carbon and oxygen isotopes reflecting the environmental conditions of that period.
If the climate or vegetation changes, the isotopic values also change and are recorded in the new layers of stalactites and stalagmites.
By analyzing these layers, we can identify precipitation patterns, temperature fluctuations, drought periods, vegetation changes, and even volcanic activity from thousands of years ago.
Analysis of Stalactites and Stalagmites
When examining a stalagmite section from the Cutta Cutta Caves in Australia, it is observed that the white and brown layers reflect changes in the chemistry of the flowing water. White layers represent periods of high rainfall, while dark layers indicate dry periods.
This stalagmite reached an average height of 330 mm and grew over 8,000 years.
It had an average growth rate of 0.041 mm per year, which is below the typical growth rate (0.1 mm/year).
This suggests limited precipitation, a cold climate, or restricted water flow inside the cave.
The color variations could indicate sudden climate changes.
By analyzing the irregularities along the central axis of the stalagmite, tectonic activities in the region can also be studied. The following cross-section belongs to a stalagmite taken from a cave in the Mersin region for paleoseismology research. The shifts in the axis dates closely align with past earthquakes in the cave’s surrounding area.
The study of these geological formations helps us understand past climate conditions and environmental changes. Additionally, it allows us to better comprehend future water movements, cave formation processes, and tectonic activities. In other words, these thousands-of-years-old natural archives enable us to read the past and shed light on the future.
