Abstract Grande Comore, the westernmost island within the Madagascar Comoros Volcanic (MCV) chain, hosts two juxtaposed basaltic volcanoes, Karthala and La Grille, with contrasting lava geochemical signatures and eruption frequencies. Their formation and dynamics have been explained either by a mantle plume or, more recently, as part of a transtensional volcano‐tectonic system. Understanding their individual development is key to resolving persistent geodynamic contradictions within the Comoros and improving volcanic hazard assessment. We integrate the morphology and spatial distribution of scoria cones with a new database of lava, and, for the first time, tephra compositions to constrain magma pathways. We classify cone‐dense regions into four main clusters (SGC, KAR, CGC, and LAG) and four sub‐clusters (KARa, KARb, KARc, and LAGa). Within Karthala, cone size weakly correlates with primitive mafic magma compositions, whereas no such relationship occurs at La Grille clusters. This indicates a developed, shallow plumbing system beneath Karthala and its absence beneath La Grille. Cone base orientation reveals that Karthala and La Grille volcanism is influenced by regional rifting, but only Karthala is influenced by edifice loading. Edifice‐induced compositional filtering promotes lateral migration of primitive magmas and vertical ascent of evolved magmas, while regionally controlled rift zones channel evolved magmas to the center of the island. Recent eruption convergence/resurgence cycles suggest that future eruptions at Karthala will likely be constrained to the edifice of Karthala while La Grille's rare eruptions have only tectonic triggers. Active areas on Grande Comore are thus well constrained and more widespread than previously thought.
Lötter et al. (Sun,) studied this question.