Additional Report for Calypso Mound

Calypso Mound

Bay of Plenty, New Zealand

37.64°S, 177.10°E; summit elev. -167 m

Calypso Mound is a white anhydrite cone some 6-8 m high, formed at 167 m depth by discharge of thermal waters at the ocean floor. It was discovered in February 1987 within one of the 'bubble zones' extending in a line from White Island to Whale Island in the Bay of Plenty.


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03/1990 (BGVN 15:03) Strong submarine hydrothermal activity


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All information contained in these reports is preliminary and subject to change.

03/1990 (BGVN 15:03) Strong submarine hydrothermal activity

The following observations, made by scientists from the USSR and New Zealand during a cruise of the RV Vulkanolog, are reported by W.F. Giggenbach and I. Menyailov.

"Calypso Mound is a white anhydrite cone some 6-8 m high, formed at 167 m depth by discharge of thermal waters at the ocean floor. It was discovered in February 1987 using the diving vessel Soucoup carried on the RV Calypso (Sarano and others, 1989). It lies within one of the 'bubble zones' extending in a line from White Island to Whale Island in the Bay of Plenty (Duncan and Pantin, 1969).

"The echograms indicated strong hydrothermal activity with a number of vents producing bubble curtains. However, an extended visual search under calm conditions from both the RV Vulkanolog and a rubber dinghy detected no bubbles at the surface. A possible explanation is re-dissolution of the gas in seawater. Similar gases, collected from more shallow submarine springs in the Bay of Plenty, S of Whale Island, and from Whale Island itself (see below), consisted predominantly of CO2, which has a comparatively high solubility in water. Re-dissolution is also supported by the distribution of reflections recorded during a slow pass over the area. Most of the individual bubble swarms, now clearly separated, appeared to terminate at ~20 m depth.

"Close inspection of a video recording shows that the fluid discharged from two vents on Calypso Mound is very likely to contain a considerable free vapor phase, indicated by flame-like tongues of free vapor, rapidly quenched on contact with cold seawater. Water leaving the vapor-seawater interaction zone appeared clear and colorless except for schlieren indicating a density difference from seawater.

"The existence of free vapor at 167 m depth and about 18 bars pressure suggests that the temperature of the fluid discharged from Calypso Mound is close to 207°C. The high proportion of vapor, apparently present in the fluid mixture leaving the vents, would indicate high corresponding enthalpies of the fluid feeding Calypso Mound. The temperature of any initial single phase liquid, before flashing and possibly present at greater depth, may therefore be considerably higher. However, Sarano et al. (1989) consider it unlikely that the waters emitted from Calypso Mound were as hot as 160°C. The 'hydrothermal' nature indicated for the Calypso Mound system may also explain the enrichment in typically 'epithermal' elements such as As, Sb, Hg, and Tl, and the absence of a 'volcanic' trace metal signature (Giggenbach and Glasby, 1977) in clays recovered from near the main cone."

References. Duncan, A.R., and Pantin, H.M., 1969, Evidence for submarine geothermal activity in the Bay of Plenty: New Zealand Journal of Marine and Freshwater Research, v. 3, p. 602-606.

Giggenbach, W.F., and Glasby, G.P., 1977, The influence of thermal activity on the trace metal distribution in marine sediments around White Island, New Zealand: New Zealand Department of Scientific and Industrial Research Bulletin, v. 218, p. 121-126.

Sarano, F., Murphy, R.C., Houghton, B.F., and Hedenquist, J.W., 1989, Preliminary observations of submarine geothermal activity in the vicinity of White Island, Taupo Volcanic Zone, New Zealand: Journal of the Royal Society of New Zealand, v. 19, p. 449-459.

Information Contacts: I. Menyailov and A. Ivanenko, IV, Petropavlovsk; W. Giggenbach, DSIR Chemistry, Petone.