Organization of volcanic plumbing through magmatic lensing by magma chambers and volcanic loads

The development of discrete volcanic centers reflects a focusing of magma ascending from the source region to the surface. We suggest that this organization occurs via mechanical interactions between magma chambers, volcanic edifices, and dikes and that the stresses generated by these features may localize crustal magma transport before the first eruption occurs. We develop a model for the focusing or “lensing” of rising dikes by magma chambers beneath a free surface, and we show that chambers strongly modulate dike focusing by volcanic edifices. We find that the combined mechanical effects of chambers, edifice loading, and dike propagation are strongly coupled. Chambers deeper than ∼20 km below the surface with magmatic overpressure in the range of 20–100 MPa should dominate dike focusing, while more shallow systems are affected by both edifice and chamber focusing.