Shape of ascending feeder dikes, and ascent modes of magma

The shape of the leading edge of an ascending feeder dike is estimated using the criterion that the direction of the movement of the edge should be perpendicular to the edge. Using this criterion it is shown that the edge can have various elliptic shapes. The ascent of magma within feeder dikes can occur in different manners. The presence of mantle derived nodules in alkalic and nephelinic magmas suggest that these magmas may ascend as a single pulse. The continuous supply to the Kilauea volcano, Hawaii suggest that the tholeiitic magma forms a 20-km high vertical column in the feeder dike, supplied from below by successive pulses of magma.