全球凍結と生物進化  [in Japanese] Snowball Earth Events and Evolution of Life  [in Japanese]

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Abstract

Liquid water on the surface of the Earth might have frozen entirely at least 3 times during the history of the Earth (650 Ma, 700 Ma, and 2.2 Ga). Assuming such extreme conditions, the snowball Earth hypothesis explains several unusual geological features associated with glacial deposits in the Proterozoic glaciations. Life should, however, have faced serious crises during these glaciations because liquid water is necessary for life. In particular, survival of photosynthetic algae, which are supposed to have appeared before the Neoproterozoic glaciations, might have been difficult if the surface water froze completely. There would have been refugia for life during the global glaciations. Life could have survived if the equatorial ocean was not completely frozen (soft-snowball condition), or equatorial sea ice might have been very thin (on the order of 10 meters). Even if these conditions were not achieved, life could have survived in shallow hot springs around volcanic islands. It would be much more difficult for eumetazoa to survive such severe conditions if they appeared before the Neoproterozoic glaciations as suggested by molecular clock studies. The appearance of eumetazoa after the last global glaciation (Marinoan glaciation), as suggested by the paleontological record, however, avoids this problem.

Journal

  • Journal of Geography (Chigaku Zasshi)

    Journal of Geography (Chigaku Zasshi) 116(1), 79-94, 2007-02-25

    Tokyo Geographical Society

References:  86

Cited by:  3

Codes

  • NII Article ID (NAID)
    10025675779
  • NII NACSIS-CAT ID (NCID)
    AN00322536
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0022135X
  • NDL Article ID
    8861006
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-169
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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