Brothers Seamount
seamount located off New Zealand
The Brothers Seamount (also Brothers Volcano) is a Pacific Ocean submarine volcano in the Kermadec Arc, 340 kilometres (210 mi) north east of New Zealand's Whakaari/White Island. It is one of the South Kermadec Ridge Seamounts.
Geology
It was formed by volcanic activity within a graben structure delimited by regional faults created by subduction of the Pacific Plate under the Australian Plate.
Within its oval outline, which measures 13 by 8 kilometres (8.1 by 5.0 mi), it contains a 3 km (1.9 mi) wide caldera with walls 300–500 metres (980–1,640 ft) high. It is three times bigger than Whakaari / White Island. A dacite dome named the Upper Cone rises 350 m from the caldera floor (which lies 1850 m below sea level), with a smaller dome just to its northeast. There is now detailed magnetic anomaly mapping of the Brothers caldera with very extreme range variation from −2000 to +2000 nT. Such mapping has shown that the local magnetic highs correlate with the morphology of the caldera, in particular its rim and the Upper Cone, whereas magnetic lows correlate with zones of hydrothermal activity and/or alteration of the rocks by the hydrothermal fluids.
Hydrothermal activity
The caldera walls and the larger dome host numerous hydrothermal vents, which send plumes of hot water 750 m up through the water column. It is the most hydrothermally active volcano known in the Kermadec Arc. These hydrothermal vents are also known as hot springs and have created an 8 meter high field of "black smoker" chimneys.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jul 20, 2026. The linked authority identifier is Q4095705. Authority coordinates are -34.882, 179.067. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1850 and 2000.
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This entry incorporates text from “Brothers Seamount” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.