Satellites tracking the pulse of northern Ecuador’s volcanoes

A study conducted by researchers from ESPOL, the University of Cagliari (Italy) and the Technical University of Manabí (UTM) used satellite radar images to investigate subtle ground movements at Guagua Pichincha, Rucu Pichincha, Pululahua and Cayambe between 2017 and 2024.

Ecuador lies within one of the most volcanically active regions on Earth. Along the Andes, volcanoes are an integral part of the landscape and everyday life for many communities. Some rise close to major cities, while others are surrounded by settlements or even have people living within their calderas. Understanding how their surfaces change over time is therefore essential for studying volcanic processes and improving volcanic hazard management.

But how can scientists detect movements of just a few centimeters across volcanic structures that stretch for kilometers? Part of the answer lies hundreds of kilometers above the Earth's surface.

Researchers from the Escuela Superior Politécnica del Litoral (ESPOL), the University of Cagliari (Italy) and the Technical University of Manabí used satellite observations to investigate ground deformation at four volcanoes in northern Ecuador: Guagua Pichincha, Rucu Pichincha, Pululahua and Cayambe.

The study, published in the international journal Environmental Challenges under the title "Deformation monitoring in northern Ecuadorian volcanoes using the InSAR technique", used radar images from the Sentinel-1 satellites to reconstruct surface changes recorded between 2017 and 2024.

The results reveal small variations in ground movement across different locations and periods. However, the researchers emphasize that these signals cannot, on their own, be interpreted as evidence of magma movement or signs of an impending eruption. Instead, they provide valuable clues about where and when more detailed observations may be needed, helping scientists identify changes that can be investigated using other monitoring techniques.

A view from hundreds of kilometers above

To detect these subtle changes, the research team used a technique known as DInSAR, or Differential Synthetic Aperture Radar Interferometry. This method compares radar images taken over the same area at different times. By analyzing changes in the radar signal, scientists can estimate whether the distance between the satellite and the Earth's surface has increased or decreased.

One of the main advantages of radar technology is its ability to collect information both day and night, even though cloud cover. This is particularly valuable in the Ecuadorian Andes, where frequent clouds, heavy rainfall, steep terrain and challenging environmental conditions can make continuous observation using optical satellites difficult.

Sentinel-1 also provides regular coverage and freely accessible data. This allows researchers to investigate large areas and complement existing observations, particularly at volcanoes where ground-based monitoring networks are limited.

Rather than comparing just two isolated satellite images, the researchers examined observations collected at different times over approximately seven years. This enabled them to reconstruct how ground movements evolved, identify trends and fluctuations, and investigate areas showing unusual patterns.

The four volcanoes were selected based on their eruptive histories, geological characteristics, proximity to populated areas and availability of data. The study focused on the Pichincha Volcanic Complex, which includes Guagua Pichincha and Rucu Pichincha to the west of Quito; Pululahua, located north of Ecuador's capital; and the Cayambe Volcanic Complex, in the Cordillera Real.

Movements of just a few centimeters — and why they must be interpreted carefully

The results show that the four volcanoes did not behave in the same way during the period studied.

At the Pichincha Volcanic Complex, the researchers detected small variations in ground movement across different areas and periods, with alternating signals indicating movement towards and away from the satellite. In volcanology, such patterns may resemble inflation and deflation — processes associated with the expansion or contraction of parts of a volcanic structure.

Guagua Pichincha showed considerable variability throughout the study period. In 2024, for example, the researchers identified an apparent inflation signal of approximately 2.46 centimeters, followed by a deflation signal of up to 4.20 centimeters.

Rucu Pichincha also displayed alternating patterns, particularly along its flanks. However, these changes do not necessarily have a volcanic origin. Some of the detected movement could be related to processes occurring near the surface, such as slope instability or seasonal changes in soil moisture.

This distinction is crucial: detecting ground deformation from space does not automatically mean that a volcano is preparing to erupt.

At Pululahua, the observations were dominated by an apparent deflation pattern, although localized episodes of inflation were also detected in areas associated with volcanic domes. During 2024, small variations were recorded that could potentially reflect the redistribution of hydrothermal or magmatic fluids. However, atmospheric conditions and the effects of complex terrain may also have influenced the measurements.

Pululahua is a particularly interesting case because people live inside its caldera, while ground-based monitoring is relatively limited. In this context, the researchers highlight the potential of satellite observations to complement existing monitoring efforts, provide regular measurements of ground movement and help guide future field investigations.

Cayambe presented an even more complex picture. Most of the observed variations were concentrated around the crater, but the volcano's ice cap makes it difficult to determine exactly what caused the signals. Snow, ice, the accumulation and redistribution of water, and other surface processes can all influence radar measurements.

The researchers therefore suggest that the fluctuations observed at Cayambe probably reflect a combination of volcanic and non-volcanic processes, rather than a single, sustained pattern of deformation.

What satellites can — and cannot — tell us

Interpreting movements of just a few centimeters from hundreds of kilometers away require considerable care. The study estimated a background noise