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Helens (MSH), Washington, USA, in 2004–2008 5, the spines at Soufrière Hills volcano, Montserrat, UK, exceeding ~40 m in 1996 6, the ~40 m spines observed at Mount Unzen, Kyūshū, Japan in 1990–1995 7, or the ~110 m high 1968 Nautilus spine at Bezymianny, Kamchatka (Russian Far East) 8, 9. Lava spines evolve to spectacular features, such as the 305 m tall spine at Mount Pelée, West Indies 4, the ~40 m tall whaleback spines at Mount St. Extrusion is commonly slow and associated with pre-eruptive outgassing and melt crystallization 3. The extrusion is accomplished by an underlying magma-filled conduit that is geometrically constrained by enveloping shear faults 1, 2. Lava spines can evolve by extrusion of low-porosity and rather solid-behaving (competent) material. Understanding the directionality of spine growth and collapse is therefore highly relevant for hazard assessment and early warning. Spines can form tall structures and gravitationally collapse, potentially generating pyroclastic density currents that affect surrounding regions. Lava spines are magma extrusions at volcanoes that allow rare insights into the conduit and conduit-bounding shear processes. The results presented here are relevant for understanding the growth and collapse hazards of spines and provide unique insights into the hidden magma-conduit architecture. We suggest that such complexities are rather common, where mechanical heterogeneities in the conduit material, mechanical erosion of the hidden spine buried by the co-evolving dome, as well as topographic (un-)buttressing controls directionality of spine growth and spine instability. Particle modeling of an extruding conduit plug highlights that the spine may have inclined to the north due to the topography and hidden architecture of the subsurface. By repeated morphology analysis and feature tracking, we constrain a spine diameter of ~300 m, extruding at a velocity of 1.7 m/day and discharge rate of 0.3–0.7 m³/s. The spine then elongates along a previously identified fracture line and bends toward the north. We show that spine growth is preceded by bulging of the dome surface, followed by extrusion in an asymmetric manner.
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Here we combine remote sensing observations with both analog and numerical experiments to describe the extrusion of a spine at the Shiveluch lava dome, Kamchatka (Russian Far East) in April-October 2020. Most volcanic eruptions occur through magma pathways that resemble tube-like conduits fed from magma sources at depth.