In short, we do not know why Hawaii has discrete islands instead of a
continuous ridge. Several untestable explanations have been offered
including: each island represents a discete blob of plume material (that is
the plume is not continuous but rather rises as a series of tear-shaped masses).
Others have suggested that once a conduit forms under a Hawaiian volcano, it
continuous lubrication keeps it open even though it may be bent. There is
earthquake data for Kilauea volcano that shows the conduit is tilted. We
have pondered this question, but do not have an answer we can test.
Does the plume's temperature vary? This would be a good explanation for the difference in size for the different Hawaiian volcanoes but we have no independent evidence for this. The volcano size may vary with the plume size.
Dr. Mike Garcia, Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu, HI 96822