It is stressed that the main difference between quiet and hyaloclastic activity is that in the former the interaction between hot lava and seawater during the eruption is minimal, whereas it is very extensive in the latter. This strong interaction is the cause of the processes which accompany hyaloclastic eruptions, processes which, in their turn, influence the chemistry and mineralogy of wide areas of the Pacific Ocean floor. Admittedly they are not well known yet, but their extensive study seems worthwhile. Two suggestions based on data presented here may be pointed out : 1) Deep-sea basaltic rocks showing breccia and/or ash-like features must not necessarily have erupted under shallow water or above sea level, as is commonly believed. 2) The "altered" or "fresh" appearance of submarine basalts is not necessarily to be ascribed to the relative age or youth of the rock. In fact extensive "alteration" of submarine lavas may commonly take place rapidly at high temperature during the eruption, rather than gradually after emplacement as is generally the case in subaerial formations. Deep-sea waters of the Pacific normally have a pH close to 7 and a rather constant low temperature, close to 0°C. Alteration of igneous minerals after emplacement under such conditions must be exceedingly slow, and concepts of "weathering" as learned in surface geology cannot be applied.

From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.

Supplement to: Bonatti, Enrico (1967): Mechanisms of deep-sea volcanism in the South Pacific. In: Abelson, P (Ed.) Researches in Geochemistry, Wiley, New York, 2, 453-491