Tag: Tonga-Kermadec

Schematic tectonic reconstruction of the Tonga-Kermadec SZI event (modified from Whattam et al., 2008). The collision of the Papua New Guinea continental block with the Loyalty-Three Kings trench is suggested to have caused a flip in subduction polarity, initiating the new Tonga-Kermadec subduction zone, possibly exploiting a weakness due to the presence of an old subduction zone. Shown are the new subduction zone (pink line), other active (solid purple lines) and inactive (dashed purple lines) subduction zones, and spreading ridges (solid red lines).

The onset of the present-day Tonga-Kermadec subduction zone occurred at around 50 Ma with the subduction of the Pacific plate under the Australian plate (e.g., Crawford et al., 2003; Whattam et al., 2008; Meffre et al., 2012). However, the date of this SZI event is highly debated, with some models suggesting that subduction was active since ~100 Ma (Schellart et al., 2006) and others that it started at ~30 Ma (van de Lagemaat et al., 2018).

Most models suggest that the Tonga-Kermadec subduction zone initiated due to the collision of the Papuan peninsula with the trench of the New Caledonia subduction zone (NE dipping subduction) at around 55 Ma (e.g., Whattam et al., 2008). This collision jammed subduction locally and caused a polarity reversal that started the Tonga-Kermadec subduction zone in the north, which progressively propagated southward (e.g., Crawford et al., 2003; Whattam et al., 2008; Meffre et al., 2012). It is also suggested that W-dipping subduction was previously active in the same region (85-65 Ma) and that collision reactivated the fossil subduction zone (Whattam et al., 2008). In this case, the event could be considered as ‘episodic subduction’, but it is here preferred to use ‘polarity reversal’ as it is the main driving mechanism.

For more details on the geologic record, corresponding plate reconstruction, and seismic tomography, see the SZI Database.

• Creators: Fabio Crameri, Valentina Magni, Matthew Domeier, Ágnes Király, Grace Shephard
• This version: 17.06.2025
• License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
• Specific citation: These graphics from Crameri et al. (2020) are available via the open-access s-ink.org repository.
• Related reference: Crameri, F., V. Magni, M. Domeier, G.E. Shephard, K. Chotalia, G. Cooper, C. Eakin, A.G. Grima, D. Gürer, A. Király, E. Mulyukova, K. Peters, B. Robert, and M. Thielmann (2020), A transdisciplinary and community-driven database to unravel subduction zone initiation, Nature Communications, 11, 3750. doi:10.1038/s41467-020-17522-9

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