Widespread secondary volcanism near northern Hawaiian Islands

Hot spot theory provides a key framework
for understanding the motion of the tectonic
plates, mantle convection and composition,
and magma genesis. The age-progressive
volcanism
that constructs many chains of islands
throughout the world’s ocean basins is essential
to hot spot theory. In contrast, secondary
volcanism, which follows the main edifice-
building
stage of volcanism in many chains
including the Hawaii, Samoa, Canary, Mauritius,
and Kerguelen islands, is not predicted
by hot spot theory. Hawaiian secondary volcanism
occurs hundreds of kilometers away
from, and more than 1 million years after, the
end of the main shield volcanism, which has
generated more than 99% of the volume of
the volcano’s mass [Macdonald et al., 1983;
Ozawa et al., 2005]. Diamond Head, in Honolulu,
is the first and classic example of secondary
volcanism.

Attempts to explain secondary volcanism
in the context of the hot spot phenomenon—
in particular, as attributed to mantle plumes—
include hypotheses of conductive heating of
the lithosphere by the plume, lateral spreading
and uplift of the plume after its ascent,
and flexure-induced
decompressional melting
related to the rapid growth of new volcanoes
above the ascending plume [e.g., Bianco et al.,
2005]. Even more enigmatic than the shield
volcanoes are recent discoveries of secondary
volcanism not being confined to the islands
but extending many tens of kilometers offshore
[e.g., Clague et al., 2000] and occurring in several
pulses [Ozawa et al., 2005].