, Volume 11, Issue 3, pp 207–215 | Cite as

Color change of lake water at the active crater lake of Aso volcano, Yudamari, Japan: is it in response to change in water quality induced by volcanic activity?

  • Shinji OhsawaEmail author
  • Takeshi Saito
  • Shin Yoshikawa
  • Hideo Mawatari
  • Makoto Yamada
  • Kazuhiro Amita
  • Nobuki Takamatsu
  • Yasuaki Sudo
  • Tsuneomi Kagiyama
Research paper


One feature of volcanic lakes influenced by subaqueous fumaroles existing at lake bottoms (called active crater lakes) is the remarkable color of their waters: turquoise or emerald green. The active crater lake named Yudamari at Mt. Nakadake of Aso volcano, Japan, takes on a milky pale blue-green. The particular blue component of the lake water color results from Rayleigh scattering of sunlight by very fine aqueous colloidal sulfur particles; the green component is attributable to absorption of sunlight by dissolved ferrous ions. An objective color observation conducted during 2000–2007 revealed that the lake water color changed from blue-green to solid green. The disappearance of the blue ingredient of the water color will result in diminution of aqueous colloidal sulfur from chemical analyses of lake waters sampled simultaneously. The aqueous sulfur is produced by the reaction of sulfur dioxide and hydrogen sulfide supplied from subaqueous fumaroles. However, its production efficiency decreases by domination of sulfur dioxide in the subaqueous fumarolic sulfur gas species with increasing subaqueous fumarolic temperature. The disappearance of blue ingredients from the blue-green color of the lake water may be attributed to activation of subaqueous fumarole activity.


Volcanic lake Color change Colloidal sulfur Iron ion Fumarole activity 



The authors are grateful to Dr. Takahiro Ohkura, Dr. Mitsuru Utsugi, Dr. Miyuki Yoshikawa, Mr. Hiroyuki Inoue, Mr. Yuki Hanamata and Mr. Taketoshi Mishima for their assistance in the lake water sampling.


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Copyright information

© The Japanese Society of Limnology 2009

Authors and Affiliations

  • Shinji Ohsawa
    • 1
    Email author
  • Takeshi Saito
    • 2
  • Shin Yoshikawa
    • 3
  • Hideo Mawatari
    • 1
  • Makoto Yamada
    • 1
  • Kazuhiro Amita
    • 4
  • Nobuki Takamatsu
    • 5
  • Yasuaki Sudo
    • 6
  • Tsuneomi Kagiyama
    • 3
  1. 1.Beppu Geothermal Research Laboratory, Institute for Geothermal Sciences, Graduate School of ScienceKyoto UniversityBeppuJapan
  2. 2.International Young Researchers Empowerment CenterShinshu UniversityMatsumotoJapan
  3. 3.Aso Volcanological Laboratory, Institute for Geothermal Sciences, Graduate School of ScienceKyoto UniversityAsoJapan
  4. 4.Department of Earth Science and Technology, Faculty of Engineering and Resource ScienceAkita UniversityAkitaJapan
  5. 5.Department of Chemistry, Faculty of ScienceToho UniversityFunabashiJapan
  6. 6.Aso Volcano MuseumAsoJapan

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