On the south-eastern flank of Iran, near the border with Pakistan, there is a mountain that for a long time remained outside the great maps of fear. The Taftan volcano has the appearance of remote places: almost 4,000 meters of rock, two main peaks, slopes marked by time, sulphurous fumaroles that remind those who pass by that something continues to breathe beneath the surface. For decades it was considered an almost extinct giant, with an uncertain eruptive history and very little ground-based instrumental data. Then, between July 2023 and May 2024, the ground near its summit rose about 9 centimeters. Very little for the eyes. A lot for a volcano.
The movement was detected thanks to radar data from the Sentinel-1 satellites, used with the InSAR technique, i.e. satellite radar interferometry: in practice, images taken at different times are compared to measure even very small ground deformations. Sentinel-1 observes the Earth’s surface day and night, even with clouds or difficult weather conditions, a decisive quality when talking about isolated and poorly monitored areas.
The signal under the summit
The study published on Geophysical Research Letters describes the first documented episode of “unrest” of Taftan, a term used in volcanology to indicate a phase of agitation of the system: the volcano changes behavior, deforms, emits more gas, shows signals outside its normality. In the case of Taftan, uplift lasted about ten months, reached rates estimated at up to 11 centimeters per year, and slowed as episodes of gaseous emissions were reported. The researchers excluded heavy rainfall or nearby earthquakes as the main causes, orienting themselves towards processes internal to the volcano.
The most interesting point lies in the depth. The geodetic model places the source of the pressure about 490-630 meters below the surface, therefore very high in the volcanic system. The deep magmatic reservoir, according to the reconstructions cited in the study, is located several kilometers further down. This makes a phenomenon linked above all to the hydrothermal system plausible: hot water, gas, fractures, altered rocks, passages that open and close like faulty valves.
One hypothesis is that the gases remained trapped in a shallow portion of the volcanic edifice, increasing the pressure in the pores and fractures of the rock. Another possibility involves a small movement of magma deeper down, enough to release gas upwards without coming close to the surface. In both cases the result changes little for those who have to monitor the mountain: the Taftan volcano has shown a new, measurable, persistent internal pressure.
Dormant, not turned off
Taftan is an andesitic stratovolcano, built along the Makran-Chagai volcanic arc, a geological belt linked to subduction, i.e. the sliding of one plate under another. The Smithsonian’s Global Volcanism Program describes it as a heavily eroded volcano, with two clear summits and active sulfur-rich fumaroles in the southeastern summit area. Its most reported elevation is 3,940 meters.
Its recent history, however, is full of gray areas. In 1902, heavy smoke and night glows were reported. In 1993, a lava flow was reported, later considered perhaps an erroneous observation of molten sulfur. The Smithsonian database records no confirmed eruptions and indicates the Pleistocene as the last known activity, with dates around 700-800 thousand years ago.
For this reason, the label of an “extinct” volcano risks reassuring too much. A volcano can remain silent for very long times and then produce signals in a few months. The silence of human chronicles weighs little when compared to the times of geology. The fumaroles, the acid springs, the degassing, the heat that continues to rise are less spectacular details than a column of ash, but they tell a simple thing: the system under the Taftan conserves energy.
The real risk is steam
The data collected so far suggests caution, not alarm. The most immediate threat indicated by scientists concerns possible phreatic explosions, i.e. explosions generated by steam when very hot water rapidly changes state and increases pressure near the surface. These events are difficult to predict well in advance and can occur even without a real magmatic eruption.
In an inhabited area, the problem also concerns gases. Sulfur-rich gusts can irritate eyes and respiratory tracts, damage crops and create discomfort in communities downwind. The city of Khash is located about 50 kilometers from the volcano, a distance that in certain wind conditions can be enough to perceive the sulphurous smells. Local reports of gaseous emissions in 2023 and 2024 have made stable surveillance even more urgent.
Taftan needs to be monitored better. Continuous measurements of gases are needed, in particular sulfur dioxide, carbon dioxide and water vapor; seismometers are needed to record small earthquakes; GPS stations are needed to follow any new deformations; updated hazard maps and clear procedures are needed for nearby communities. Satellite images turned on the light. Now we need tools on the ground.
Satellites and distant mountains
The Taftan volcano case also shows how much surveillance of remote volcanoes has changed. In the past, an isolated mountain, without a network of sensors installed on site, could move for months without leaving any legible traces. Today a radar satellite can see a few centimeters of deformation on enormous surfaces, even where physically reaching is difficult. The InSAR technique is used precisely to map ground deformations and becomes precious during volcanic crises, because it also works at night and in bad weather.
This does not replace field work. It completes it. The satellite sees the big picture, measures the swelling, intercepts the change. The instruments installed on the volcano tell if the gases are increasing, if the microearthquakes are growing, if the pressure is releasing or continuing to accumulate. If the ground begins to subside, it could indicate a reduction in pressure. If the lift resumed or accelerated, the signal should be read more carefully. If gas and seismicity changed together, the level of surveillance would need to rise.
Many volcanoes around the world go through phases of turmoil without erupting. Others remain quiet for years and then quickly change pace. The difference is often made by the quality of the monitoring. A mountain observed continuously gives margin. A mountain left alone becomes an administrative surprise, as well as a geological one.
The volcano is located in a country already affected by war and strong diplomatic pressure. The scientific data remains the same: 9 centimeters of lifting, gas, microearthquakes to follow, instruments to put in the field. The context in which that data must be managed changes. When public and political attention is absorbed by the conflict, even a slowly moving mountain can end up on the sidelines.
The Taftan, for now, has done something small and enormous at the same time: it has moved 9 centimetres. Enough to get out of the comfortable category of forgotten volcanoes. Enough to remember that a mountain can be silent for a long time and still continue to keep its breath warm under the skin.
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