The Tarama Knoll: Geochemical and Biological Profiles of Hydrothermal Activity

Toshiro Yamanaka, Hiromi Nagashiov, Ryu Nishio, Kazuna Kondo, Takuroh Noguchi, Kei Okamura, Takuro Nunoura, Hiroko Makita, Kentaro Nakamura, Hiromi Watanabe, Kazuhiro Inoue, Tomohiro Toki, Kouichiro Iguchi, Urumu Tsunogai, Ryoichi Nakada, Shogo Ohshima, Shin Toyoda, Jun Kawai, Naohiro Yoshida, Akira IjiriMichinari Sunamura

Research output: Chapter in Book/Report/Conference proceedingChapter

7 Citations (Scopus)


Tarama Knoll is located about 60 km north of Tarama Island, Sakishima Islands, southwestern Japan. The knoll has an almost conical shape, with foot and summit depths of 2,000 and 1,490 m (total relief ¼ 510 m) from the sea surface, respectively. This area has been identified as a possible active submerged volcano called “Tarama Knoll” (Otani et al. 2004). However, there are actually two separate knolls in the area. This knoll is located northeast of the other, which is named Tarama Hill. During the KT05-26 cruise on the R/V Tanseimaru, a methane anomaly was detected near the seafloor around the area and was considered to be of possible hydrothermal origin. Based on visual observation of the seafloor and its bathymetry, this knoll is considered a pumice cone. Dense turbid water is often observed around summit of the knoll, and a methane anomaly was detected in the water. These observations suggest that the turbid water is a hydrothermal plume. An ironrich, red-brown sediment-covered area was discovered at a depth of 1,510–1,540 m on the southwestern slope near the summit. At the red-brown sediment area, a weak shimmering of clear fluid could be observed, and the fluid temperature reached 20 _C. Sampled shimmering fluid showed a high silica concentration (_1 mM), indicating an interaction between the fluid and the surrounding rock. These chemical data support the occurrence of active hydrothermal circulation at Tarama Knoll.

Original languageEnglish
Title of host publicationSubseafloor Biosphere Linked to Hydrothermal Systems
Subtitle of host publicationTAIGA Concept
PublisherSpringer Japan
Number of pages8
ISBN (Electronic)9784431548652
ISBN (Print)9784431548645
Publication statusPublished - Jan 1 2015


  • Hydrothermal activity
  • Hydrothermal plume
  • Southern Okinawa Trough
  • Tarama Knoll

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)


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