Geology & Geophysics Research Spotlight

Bending Plate Provides Unexpected Heat Source

Scientists discover the causes for heat flow anomalies near the Japan Trench.

Source: Geochemistry, Geophysics, Geosystems

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Near the Japan Trench, a subduction zone where the dense oceanic Pacific plate plunges beneath the relatively light continental Okhotsk plate, the flow of heat is unexpectedly high. Kawada et al. constructed a thermal model explaining that hydrothermal circulation causes this heat flow anomaly.

Scientists have conducted heat flow surveys near the Japan Trench and discovered that the heat flow within 150 kilometers of the trench is higher than would be expected on an abyssal plain of the same age. The authors constructed a model and showed that this discrepancy can be explained by taking into account additional sources of heat transport, namely, enhanced hydrothermal circulation.

This happens because, as the plate nears the trench, it bends, which enhances the permeability of the crust. Water can thus circulate more deeply and be heated. This enhanced heat flow does not appear to significantly affect the thermal structure of the main subduction zone. (Geochemistry, Geophysics, Geosystems, doi:10.1002/2014GC005285, 2014)

—Catherine Minnehan, Freelance Writer

Citation: Minnehan, C. (2015), Bending plate provides unexpected heat source, Eos, 96, doi:10.1029/2015EO036435. Published on 1 October 2015.

© 2015. The authors. CC BY-NC 3.0
  • Charles Corry

    When we first made heat flow measurements leading up to the Japan Trench we speculated that the increased heat flow was caused by the flexure of the plate as it was bent before diving into the trench. But those were early days for sea floor spreading and I’ve lost my copy of our writeup Vacquier, V., Uyeda, S., Yasui, M., Sclater, J. G., Corry, C. E., and Watanabe, T., 1966, Heat flow measurements in the northwestern Pacific: Bulletin of the Earthquake Research Institute, Tokyo, v. 44, p. 1519-1535, so I don’t know if we published the idea. Nice to find that Kawada et al. have quantified our speculation.

    • Graeme Beardsmore

      Charles, it’s amazing what you can find online these days:
      http://repository.dl.itc.u-tokyo.ac.jp/dspace/bitstream/2261/12307/1/ji0444008.pdf
      The paper contains no speculation about the cause of the anomalies.

      • Charles Corry

        Thanks! Looking at the ship’s track brings back memories of a rough spring cruise in the North Pacific while Vacquier was measuring magnetic inclination over the Emperor Seamounts. At times the R/V Argo was rolling through a 110° arc. Almost went over the fantail deploying the magnetometer after one heat flow station.
        It was also the first time we attempted to measure thermal conductivity in situ.