Thermal activity in volcanoes is one of the most spectacular and fascinating natural phenomena on our planet. From bubbling hot springs to geysers that shoot columns of water and steam into the sky, these processes offer us a window into the Earth's internal energy, and are a visible reflection of the intense underground heat bubbling beneath our feet.
When we talk about terms like hot springs, geysers, and volcanic geological processes, we're referring to a group of surface manifestations that, in addition to providing beauty, are of enormous scientific, educational, and energetic value. Throughout this article, you'll discover how they form, the secrets behind their functioning, their ecological importance, and how humans have harnessed them, as well as the risks associated with their use or visit.
Hotspots: Why do thermal events occur?
The source of all volcanic thermal activity lies within the Earth, where geothermal energy results from the decay of radioactive elements and the heat left over from the formation of the planet. This energy travels to the surface through conduction and convection processes through the rock layers. However, not all regions of the globe exhibit the same thermal characteristics. These manifestations are especially abundant in areas where the Earth's crust is fractured or close to magma, that is, in areas with recent volcanic activity, tectonic plate boundaries, and hot spots.
The Earth's surface reveals the underground heat through various expressions: geysers, hot springs, fumaroles, mud pools and steaming floors. They all have in common the existence of an internal heat source, water, and a network of permeable fissures that allow hot fluids or vapors to rise. Emblematic examples of these areas are Yellowstone (USA), El Tatio (Chile), Iceland, New Zealand and the circum-Pacific region known as the Ring of Fire.
Hot springs: the most widespread manifestation
Hot springs, also known as thermal springs, represent the most common thermal manifestation worldwide. These are points where groundwater, after being heated at a depth of several kilometers (either by contact with magma, hot igneous rocks, or the normal geothermal gradient), rises and emerges at the surface, discharging at temperatures higher than the local average.
The modern definition of a hot spring states that its temperature must be at least 5°C higher than the annual average temperature of the location. However, The temperature can vary greatly: from mild to scorching, exceeding 90°C in some extreme cases.. In addition, the chemical compositions also differ: there are acidic, alkaline, or neutral springs, depending on the pH of the water, and they can be classified according to the dominant compounds (bicarbonates, sulfates, chlorides, etc.).
A fascinating feature of hot springs is the wide range of dissolved minerals they carry. These minerals are deposited in the surrounding area, forming terraces of silica, carbonates, and other spectacular formations, such as the famous Grand Prismatic Springs in Yellowstone or the natural spas of Pamukkale in Türkiye.
Hot springs have also played a prominent role in human culture and health. Its mineral-rich waters have been used since ancient times for therapeutic and medicinal baths, and even today they are the main attraction of numerous spas and tourist centers throughout the world.
Geysers: a geological spectacle in eruption
Among all thermal manifestations, geysers occupy a privileged place thanks to their spectacular nature. A geyser is a special hot spring capable of periodically shooting jets of hot water and steam to great heights. However, their existence is truly rare: fewer than a thousand are known in the world, and they all share a series of very specific geological and hydrogeological conditions.
How do geysers work? The key lies in a precise combination of underground heat, abundant water, and a network of narrow, convoluted underground conduits. Water, infiltrated from the surface, descends to hot zones where it is trapped in cavities under pressure and heated by contact with magma or hot rocks. When the temperature exceeds the boiling point under high-pressure conditions, some of the water suddenly turns to steam, pushing the rest to the surface in a violent eruption that can reach tens of meters in height.
The eruptive cycle is cyclical: After each eruption, the geyser must recharge with water, building pressure and heat until the next explosion. This process can be repeated every few minutes, hours, or even days, depending on the specific geyser.
Types of geysers
- Cone geysers: They expel jets of water and steam relatively frequently and form a conical mound of mineral deposits, mainly silica, around their mouth.
- Fountain geysers: They exhibit more explosive and less regular eruptions, erupting into surrounding pools of water rather than through a cone.
Famous examples include Old Faithful in Yellowstone, famous for its regularity, Steamboat (the tallest in the world at 91 meters), and the El Tatio geyser field in Chile. Other countries with significant geysers include Iceland, Russia, New Zealand, and Japan.
Geysers outside the Earth: Curiously, extraterrestrial geysers have also been observed on moons such as Triton (Neptune) and Enceladus (Saturn). In these cases, they do not expel liquid water, but rather nitrogen or water vapor through cryovolcanoes, driven by mechanisms other than volcanic heat but equally fascinating.
Fumaroles, solfataras and other gaseous manifestations
In addition to water and steam, volcanic areas show direct escapes of gases through fumaroles. These steam and gas surges include not only water vapor, but also sulfur dioxide, hydrogen sulfide (H2S), CO2 and other volatile compounds. The oxidation of hydrogen sulfide is responsible for the intense colors and yellow sulfur deposits that surround many fumaroles, such as those in Iceland or in the Italian solfatara fields.
Sometimes, if boric and hydrogen sulfide acids predominate, the fumaroles may be given the specific names sofioni and solfataras, respectively. The intense chemical activity of the fumaroles modifies the rocky environment, generating surreal landscapes and altering the surface mineralogical composition.
Mud pools and vaporizing floors: the mud of energy
Mud pools and steaming floors are equally fascinating expressions of hydrothermal activity. When thermal water is scarce, but hot underground steam is abundant, this steam rises, dissolving the surrounding rocks and transforming them into clays and silica. Water and fine minerals are mixed to form high or low viscosity sludge, the consistency and color of which depend on the water, sulfur, and iron oxide content. In some cases, the bubbling of the mud produces small mud volcanoes.
Vaporizing soils, on the other hand, are soils saturated with vapor from deep deposits. They are potentially dangerous, as the surface can be fragile and easily collapse, and temperatures just a few centimetres from the ground can exceed 90°C. Therefore, Exploring these areas requires strict precautions and often the presence of specialized guides.
Geological processes and necessary conditions
For a surface thermal manifestation to exist, a series of essential geological factors must be present:
- Heat source: Typically magma or hot igneous rocks associated with recent volcanic activity or anomalous geothermal gradient.
- Presence of water: supplied by filtration of precipitation, rivers or underground reservoirs.
- Permeable duct and fissure systems: They allow the circulation and accumulation of water to hot areas, as well as its return to the surface.
- Suitable pressure and hydrodynamic conditions: essential for sudden boiling and eruption to occur in the case of geysers.
Aquifers confined between impermeable layers of rock are key to the pressure buildup that results in periodic geyser eruptions. Changes in any of these factors, whether due to natural or human causes, can drastically change the behavior or even extinguish thermal manifestations.
Relationship between volcanic activity and geothermal sources
Volcanic regions are especially prone to geothermal vents and thermal activity due to the presence of young or cooling magma chambers. The heat released warms groundwater, which rises as steam or liquid water. Thus, Recent volcanism, in addition to generating eruptions and new landscapes, constantly feeds these mineral- and energy-rich hydrothermal systems.
Worldwide distribution: Where to find these wonders?
The distribution of these phenomena is not uniform. They are mainly concentrated in:
- Subduction zones and destructive plate boundaries: Like the Pacific Ring of Fire, the Andes, Japan, western North America, etc.
- Hotspots and mid-ocean ridges: Iceland, Hawaii and the seabed of the Gulf of California offer striking examples.
- Major continental systems: Yellowstone in the USA, the El Tatio geothermal field in Chile, and the geysers of New Zealand are the most iconic examples.
On the ocean floor, hydrothermal activity creates underwater chimneys with temperatures exceeding 300°C, creating unique ecosystems at great depths.
Ecological impact and associated biodiversity
Thermal environments are surprising hotbeds of biodiversity, often dominated by extremophile bacteria and microorganisms adapted to extreme temperatures and chemical compositions. These communities form the basic support for complex food chains, both on the surface (such as on the colored edges of springs) and in deep areas of the ocean (tubeworms, mollusks, fish, bacteria that metabolize hydrocarbons or minerals).
The deposited mineral compounds, temperature and pH determine life, determining who can survive and who cannot. For example, the reddish, orange, and green colors in Yellowstone hot springs are the result of specialized bacterial and algal pigments.
Geysers and hot springs as energy sources
One of the major modern interests of thermal activity is the use of geothermal energy to generate electricity and heating sustainably. Geothermal plants extract hot water and steam from these underground systems to drive turbines or provide direct heat. Countries such as Iceland, Italy, New Zealand, Mexico, Chile, the United States, and Kenya have developed significant geothermal infrastructure, especially in active volcanic areas.
Advantages of volcanic geothermal energy:
- It is renewable and not dependent on the weather.
- It emits very low amounts of greenhouse gases, helping to combat climate change.
- It allows the stable and continuous generation of electricity.
- Reduces carbon footprint compared to fossil fuels.
However, it is not without risks: unexpected volcanic eruptions, induced earthquakes, toxic gas emissions or landscape alterations.
Social, cultural and medical benefits
In addition to their scientific value, hot springs have historically been used for medicinal and recreational purposes. Numerous spas in Europe, Asia, and America are located near natural hot springs, taking advantage of the mineral wealth for therapeutic baths to treat joint, skin, and muscle ailments.
The tourist attraction of these places is enormous. National parks like Yellowstone, geothermal parks in Iceland, and Japanese onsen hot springs receive millions of visitors annually. Its cultural and spiritual value also forms part of the intangible legacy of many peoples.
Dangers, conservation and threats
Thermal manifestations can be as dangerous as they are beautiful. High temperatures, acidic waters and unstable soils can cause serious or fatal accidents. It is essential to follow safety instructions in the parks and stay on designated trails.
These natural wonders are threatened by overexploitation, climate change, and pollution. Massive groundwater extraction can result in the extinction of geysers (as has happened in parts of New Zealand or Nevada, USA). Large hydroelectric projects, geothermal well drilling, and uncontrolled tourism activities can disrupt the delicate balance that sustains these systems.
For this reason, many countries have given special protection to these enclaves, declaring them national parks or scientific reserves. Constant monitoring, tourism regulation, and sustainable management are essential to ensure its long-term survival.
Changes and evolution over time
Thermal activity is not static. Geysers can change the frequency, duration, and intensity of their eruptions due to natural changes in the hydrogeological system or human-caused effects. They can even become extinct and re-emerge after decades of inactivity, depending on variations in water supply, groundwater pressure, or the input of magmatic heat.
Long-term study of these systems provides valuable data on deep geological processes, local climate changes, and the effects of seismic or volcanic events on thermal dynamics.
Frequently asked questions about thermal activity in volcanoes
What is a geyser? It is a hot spring that, thanks to the accumulation of pressure and heat, periodically ejects jets of water and steam through an opening in the surface.
Where are there more active geysers? Yellowstone Park is home to the largest concentration of glaciers in the world, but Iceland, Chile, Russia, Japan, and New Zealand are also notable.
Are geysers and hot springs dangerous? Yes, its high temperature, acidity, and unstable soil can cause serious injuries. It's essential to respect signs and follow safety regulations.
How is the energy of these phenomena harnessed? Through geothermal plants, which extract steam and hot water from deep aquifers for electricity generation and district heating.
Can geysers become extinct? They can disappear due to natural changes in underground systems or due to human action, such as overexploitation of aquifers or alterations in water flow.
Can they be found on other planets? Yes, although driven by other mechanisms, “geysers” have been detected on icy moons in the solar system such as Enceladus and Triton.
Geological and hydrogeological indicators: what geysers reveal
The presence of geysers and hot springs reveals deep and active geological processes. They allow geologists to:
- Identify areas of recent volcanic or tectonic activity.
- Delimit heat sources potentially exploitable for geothermal energy.
- Study the alteration of rocks and the formation of new minerals.
- Monitor environmental changes, as they are sensitive to variations in precipitation, seismic movements, and local climate changes.
Examples, technical details and interesting facts
Around the world there are numerous points of interest linked to geothermal activity:
- Yellowstone, USA: more than 500 active geysers and thousands of hot springs.
- El Tatio, Chile: the largest geyser field in the southern hemisphere, at an altitude of over 4.000 metres.
- Dolina Geiserov, Russia: valley with a hundred geysers in the heart of the Kamchatka Peninsula.
- Iceland: territory plagued by hot springs, mythical geysers like the one that gives their name to all of them (Geysir) and a huge national geothermal network.
- New Zealand (Taupo/Rotorua): A must-see destination for those who want to see steam fields, bubbling mud, colorful fountains, and regular eruptions.
The operation of these systems is so delicate that small changes in the water supply or the structure of the conduits can cause a geyser to shut down, change its flow rate, or become a simple warm fountain.
Responsible use and future of volcanic thermal activity
The commitment to geothermal energy as a sustainable energy source is growing year by year. To achieve balanced development, it is essential to combine the economic exploitation of resources with the conservation of natural environments and scientific research.
The challenge is to ensure that these unique landscapes continue to function unaltered and inspire future generations, providing health, clean energy, and insight into the deepest processes of our planet.
Thermal activity in volcanic areas is a striking example of the connection between the Earth's internal processes and life on the surface. From hot springs to spectacular geysers and geothermal exploration, to their ecological importance and associated risks, these phenomena remind us that our planet is alive and that respect and curiosity are the best tools for exploring and caring for it.