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Cosmic-ray muons penetrate large rock volumes, provide measurable fluxes through hundreds of metres of material, and their attenuation encodes density and thickness information. Proof-of-concept studies have already demonstrated that muography can support geoscientific applications (e.g., [1]). Here, we highlight recent results from our geoscientific studies and demonstrate the versatility of muography in characterizing density and structural changes and dynamics in Earth’s subsurface.
At the active Sakurajima volcano (Japan), we studied how magma moves beneath the craters by combining satellite measurements of ground movement with muography [2]. We observed that magma first moved sideways beneath the craters and later rose toward the surface, influencing which crater was active at different times. Our results indicate the presence of both a magma pathway at ~700 m depth, and a shallow magma storage zone at ~350 m depth that feeds all eruptions at Sakurajima. The combined use of ground deformation data and muography shows promise as a complementary approach for monitoring shallow volcanic processes and gaining insights into eruption behavior.
Volcanoes can remain unstable long after eruptions, and weakened slopes may collapse, causing dangerous landslides. At Mount Unzen (Japan), we used muography for structural characterization [3]. The results showed that lava lobes deposited on the volcanic edifice are less dense than the volcano’s rock, confirming structural weakening of lava lobes after past eruptions. By comparing these measurements with rainfall data, we found no signs of rain-triggered instability during the study period. Long-term muography can help assess volcanic stability and landslide risk.
Studying ophiolites provides insights into the physics and geology of the currently inaccessible oceanic crust-mantle structure [4]. Muography of a crust-mantle transition zone at Wadi Fizh in the Samail ophiolite in Oman revealed a highly serpentinized Moho [5], in contrast with petrological profiles which previously revealed gradational transition from the mantle to the crust at Wadi Fizh. Moreover, a higher density zone was revealed beneath the ophiolite ridge, indicating the presence of fresh peridotites beneath the thin layer of gabbroic cover. Muography can provide complementary density information about the ophiolites and, by extension, about the architecture of the oceanic lithosphere.
All these examples show that muography provides a quantitative approach for observing material distribution and movement across diverse geological settings, and offers insights into both static structures and dynamic processes.
[1] Oláh, L., Tanaka, H.K.M., Varga, D. Muography: Exploring Earth's Subsurface with Elementary Particles (2022). https://agupubs.onlinelibrary.wiley.com/doi/book/10.1002/9781119722748
[2] Oláh, L., Nakamichi, H., Ohminato, T., Tanaka, H.K.M., Varga, D. Magma migration beneath the active craters of Sakurajima volcano before the 2023 eruption of Showa crater inferred from ground deformation and muon monitoring. Earth Planets Space 77, 196 (2025a). https://doi.org/10.1186/s40623-025-02325-3
[3] Oláh, L., Tercsi, L., Varga, D., Tanaka, H.K.M, Kubo, S., Yoshida, S., Iwata, K., Akanuma, J., Kaneko, M., Watanabe, H. Muography for structural characterization of volcanoes: a case study at Mount Unzen, Japan, Geophysical Journal International 244, ggaf482 (2026). https://doi.org/10.1093/gji/ggaf482
[4] Oláh, L., et al. Plans for Muography of Samail Ophiolite. Journal of Advanced Instrumentation in Science, (2024). https://doi.org/10.31526/jais.2024.499
[5] Oláh, L., et al. First cosmic-ray muography of a crust-mantle transition zone (2025b). Preprint available at Research Square https://doi.org/10.21203/rs.3.rs-8019975/v1