Convective tipping point initiates localization of basaltic fissure eruptions

Basaltic fissure eruptions may evolve rapidly and unpredictably complicating hazard management. Localization of an elongate to one or more focused vents take days months, depends on fluid dynamic processes, such as thermally-driven viscous fingering, in the sub-volcanic plumbing system. However, dynamics a dyke geometry are poorly understood. We perform scaled analogue experiments investigate convective magma exchange flow within dyke-like conduit, discover regimes ranging from chaotic mingling stable, well-organized exchange, over parameter space relevant for natural eruptions. Experiments via Grashof number Gr, which is Reynolds buoyancy-driven flows. propose that at high Gr hinders localization by suppressing whereas organization low enhances localization. Consequently, progressive decrease through increasing viscosity decreasing width pushes eruption towards tipping point results rapid Our findings indicate current conceptual models require revision account this point, provide quantitative framework understanding evolution