Abstract

The dike complex in the eroded Koolau tholeiitic shield volcano is unique among: described dike swarms for its coherence, high dike-injection intensity, relatively uniform and non-Gaussian 50% to 65% intensity level, and lack of dike divergence. Parts are like a sheeted-dike complex, though high in an intraplate volcanic edifice.

A model is proposed in which highly mobile tholeiitic magma, having considerable freedom to move through the strongly disjointed volcano, seeks zones in which it is gravitationally most stable. These zones are marginal parts of the dike complex, separating lavas having a lower-than-magmatic bulk density from a >50% dike complex having a higher-than-magmatic bulk density. This model also explains the strong propensity for the magma of Kilauea volcano to remain underground (in a gravitationally stable zone). Magma erupts only when it vesiculates sufficiently; often, when it has degassed, some of it promptly plunges back toward the stable zone again.

You do not currently have access to this article.