Manganese stains, crusts, and nodules are widely distributed on
the insular slopes of the Hawaiian ridge. The thickness of the manganese crusts
depends on depth of water, water circulation, and the age and lithology of
the substrate, and varies from absent to stains off the island of Hawaii to a
maximum of 5 cm in the vicinity of Midway. Scanning electron microscope
studies indicate that the internal structure of the manganese crusts is relatively
featureless compared with that of deep-sea manganese nodules. Reconsideration
of ages of manganese deposits from the Hawaiian archipelago indicates
that the rates of accretion of manganese crusts are probably in the same range
as those of deep-sea deposits and that the crusts do not accrete at a much faster
rate than deep-sea deposits as previously suggested. Iron staining is observed
in the volcanic substrates and becomes more apparent with the increasing age
of the substrate. There appears, however, to be no evidence that iron oxide is
a ubiquitous control factor in initiating manganese crustal growth. Because
of the terrain and the rocky nature of the substrate, diagenetic processes
within the sediment column probably play no major role in controlling the
composition of manganese crusts on the flanks of the island ridge
