Theory of water-filled crevasses in glaciers applied to vertical magma transport beneath oceanic ridges

Abstract

The theory describing the behavior of glacier crevasses that are partially filled with water is developed further, and the results are applied to the problem of vertical magma transport beneath oceanic ridges. It is assumed that lava collects beneath the center of a ridge. According to the theory, if a tensile stress acts across a ridge that is cold enough to behave like an elastic plate, a crack filled with liquid rock will nucleate at the bottom surface of the plate. This crack will increase in length and volume, pinch its lower end shut, and finally rise toward the top surface. (The immediate driving force causing the crack to rise is the Peach-Koehler force, which acts on dislocations. In the case of the liquid-filled crack the Peach-Koehler force produces a total, pseudo-Archimedian force that is identical in form to the true Archimedian buoyancy force on a solid within a liquid.) Eventually the crack will stop, and the lava in it will freeze and cause the oceanic ridge to spread somewhat. Lava will spill out onto the top surface only if an oversize crack reaches the upper surface. A crack that has been preceeded by other cracks on its upward journey will be trapped in the interior of the plate and its lava will freeze in place.