The temperatures in underground caves are generally stable due to the thermal inertia of the ground and the lack of direct impact from external weather conditions.
The rocks surrounding the caves are often excellent thermal insulators. They are very dense and thick, making them particularly poor conductors of heat, thus significantly slowing down thermal exchanges between the inside and the outside. As a result, even if it is freezing outside or if the sun is beating down, heat or cold take a long time to pass through this rocky wall. The result: the temperature inside remains fairly constant. Moreover, the rocks slowly accumulate thermal energy that they gradually release, forming a kind of natural thermal buffer that prevents sudden temperature changes. It's a bit like having a super thick blanket around the cave, insulating it from the whims of surface weather.
Underground, the brutal variations in temperature, storms, and even rain have almost no direct impact. On the surface, weather changes quickly alter the temperature, but deep down, rocks act as a thermal shield. Essentially, heat or cold takes so long to penetrate the thick rock layers that by the time the weather effect finally reaches them, the seasons have already changed above. This time lag creates a kind of "natural filter" that smooths out all the rapid fluctuations. As a result, underground, everything remains relatively calm and constant, no matter what happens up there.
In caves, high humidity plays a key role in thermal stabilization. The water present in the rocks and the surrounding air gradually stores and releases heat. This phenomenon of storage, called thermal inertia, smooths out temperature variations: when it's hot outside, the water gently absorbs this heat, without large fluctuations, and slowly releases it when it's cold. Groundwater flows, often constant in temperature, also provide additional thermal stability by significantly limiting internal temperature fluctuations. It's like a natural thermostat that prevents caves from heating up or cooling down too quickly.
The air in a cave constantly exchanges its heat with the surrounding rock walls. When the indoor air warms slightly, it transfers some of its heat to the cooler rock. Conversely, if the air cools down, it is the walls that will give it back some heat. The rocks, thanks to their thermal inertia, absorb and slowly store energy, slowing down temperature variations. These thermal exchanges are continuous but very gentle, ultimately ensuring a generally stable and regular indoor climate.
The deeper you go underground, the more the temperature becomes stable. Just a few meters below the surface, daily and seasonal temperature variations become imperceptible. Why? Because the upper layers of rock act as a huge insulating blanket that protects the lower areas from external fluctuations. From a certain depth, generally around 10 to 20 meters depending on the regions, the temperature remains practically the same throughout the year. This is known as the thermal stability zone. Even deeper, the temperature rises slightly but steadily with depth: this is the famous phenomenon of the geothermal gradient, which causes the temperature to increase by about 1 °C every 30 meters on average. As a result, at depth, temperature is in a state of calm, regardless of the weather above ground.
The thermal stability of caves makes them a potential option for long-term storage projects of seeds, computer servers, or even archives and precious works of art.
There are animal species adapted to life exclusively in caves (troglobites), which depend entirely on these stable conditions for their survival, such as certain species of fish and insects that are devoid of pigmentation and vision.
The temperatures in underground caves generally approximate the average annual temperature of the region; thus, they remain practically constant throughout the year, with little variation even in the depths of winter or summer.
The deepest known cave to date is the Veryovkina Cave in Georgia, which exceeds 2,200 meters in depth. Despite this extreme depth, the temperature at the bottom remains surprisingly stable at just a few degrees above freezing.
Sure. Here’s the translation: "Yes. Groundwater has a high thermal inertia. Its presence greatly contributes to maintaining stable temperatures by slowly absorbing or releasing heat."
The sensation of cold primarily comes from high humidity. Humid air enhances thermal conduction to the skin, creating the impression of a lower perceived temperature than the actual temperature.
Yes, underground caves in warm regions tend to be cooler than the outside, as their temperature reflects the average climate of the area rather than the extreme heat of the day.
In general, just a few meters underground, seasonal variations become negligible. Beyond 10 to 20 meters, the temperature usually remains constant, close to the average annual temperatures at the surface above.
Absolutely. This stable thermal property is utilized, for example, in geothermal energy to naturally heat or cool certain homes, thereby significantly reducing energy consumption.
Very faintly. Generally, caves maintain stable temperatures throughout the year, with only slight fluctuations near the entrances or at the surface. The deeper you go, the less noticeable these variations become.
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