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Author: Fabio Crameri

Halmahera (East Molucca) subduction zone initiation

The Halmahera SZI event is suggested to have occurred at ~15 Ma, which is still controversial, possibly through episodic subduction.

Schematic tectonic reconstruction of the Halmahera SZI event (modified from Hall, 1996 and Hall and Smyth, 2008). Subduction of the Molucca Sea plate started close to a transform boundary, initiating the new Halmahera subduction zone. Shown are the new subduction zone (pink line), other active subduction zones (solid purple lines), and transform faults (red dashed lines).

The Halmahera subduction zone initiation (SZI) event – associated with the subduction of the Molucca Sea plate eastwards beneath the Philippine Sea plate – was previously estimated to have initiated at around 17–15 Ma (Baker & Malaihollo 1996; Hall, 1996), but more recent studies have alternatively suggested a younger age of ~10-7 Ma for SZI (Chandra & Hall, 2016; Hall & Spakman, 2015; Zhang et al. 2017). Given the evidence presented below, SZI must be older than 11 Ma. Considering a ~5 Myr delay (in line with Baker & Malaihollo 1996) we suggest ~15 Ma as our best-estimate for Halmahera SZI, but emphasise that this preference is likely to be controversial and may be revised downward if additional evidence demonstrates a disconnect between the oldest arc volcanism (on Obi Island) and later subduction beneath Halmahera. The type of SZI is also unclear, but could be ascribed to episodic subduction, as there is evidence of subduction along Halmahera from the Mesozoic to the Oligocene. That subduction ceased by the time of a regional plate boundary reorganisation at about 25 Ma, whereafter subduction initiated on the western side of the Molucca Sea plate, along the Sangihe arc (Hall and Smyth, 2008). Hall and Smyth (2008) suggested that Halmahera SZI was caused by locking of the Sorong fault zone along the southern edge of the Molucca Sea. Considering the broader geodynamic picture, Halmahera SZI occurred perhaps within ~20° of the Manus plume (Wu et al. 2016), and approximately above the edge of the Pacific LLSVP (i.e., along the edge of its surface projection, according to its present-day shape).

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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Aleutian subduction zone initiation

The Aleutian subduction zone initiation event formed today’s Aleutian trench, occurred at around 53 Ma through subduction polarity reversal.

Schematic tectonic reconstruction of the Aleutian SZI event (modified from Domeier et al., 2017). The collision of the Olutorsky arc with the trench of the south-dipping subduction of the Eurasia plate below the Pacific Plate is suggested to have caused a flip in subduction polarity, initiating the new Aleutian subduction zone. Shown are the new subduction zone (pink line), other active (solid purple lines) and inactive (dashed purple lines) subduction zones, spreading ridges (solid red lines), and transform faults (red dashed lines).

The Aleutian subduction zone initiation event formed today’s active Aleutian trench. The onset of the subduction zone likely occurred at around 53 Ma (Davis et al., 1989; Jicha et al., 2006) when the Pacific and Kula plates began to subduct northward, and at some point, under the overriding continental plates of northeast Siberia and North America.

The Aleutian SZI event was possibly instigated as a subduction polarity reversal associated with the arrival of an intraoceanic arc (Olutorsky arc) to the Okhotsk-Chukotka-Beringian margin of northeastern Asia and northwestern North America (Scholl, 2007; Domeier et al., 2017; Vaes et al., 2019), and therefore may have formed close to (i.e., at a distance of around 300 km) a pre-existing convergent plate boundary. Vaes et al. (2019) have speculated that the Aleutian trench may have exploited a pre-existing transform boundary in a possible backarc behind the Olutorsky arc. Those authors have furthermore pointed out that arc volcanics with ages of 54.4 Ma to 50.2 Ma have been dredged from the Beringian margin (Davis et al., 1989), and note that the Aleutian SZI event could also be seen as the outboard jump of that Beringian subduction zone.

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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Tonga-Kermadec subduction zone initiation

The Tonga-Kermadec subduction zone initiated likely due to a subduction-polarity reversal at around 50 Ma.

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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Sunda-Java subduction zone initiation

The Sunda-Java SZI event might have re-started subduction at the southern margin of Sundaland at around 60–40 Ma.

Schematic tectonic reconstruction of the Sunda-Java SZI event (modified from Hall, 2012). Subduction of the Indo-Australian plate at the Sundaland margin has been episodically ongoing since >100 Ma. The most recent episode occurred at ca. 40–60 Ma and it initiated the new Sunda-Java subduction zone. Shown are the new subduction zone (pink line), other active (solid purple lines) and inactive (dashed purple lines) subduction zones, spreading ridges (solid red lines), and transform faults (red dashed lines).

The Sunda-Java SZI event might have re-started subduction at the southern margin of Sundaland with the Indo-Australian plate sinking below the Eurasian plate at around 60–40 Ma (50 Ma is taken as the approximate average of the below timings). This subduction zone eventually evolved into the presently active Sunda-Java subduction system (Hall, 2012; Heine et al., 2004; Zahirovic et al., 2016).

It is generally agreed that the earlier accretion of the Woyla arc to Sundaland was followed by a hiatus in subduction along the margin. However, the absolute timings are debated. Hall (2012) initiate subduction along Sundaland (Sunda-Java described here) at 45 Ma (hiatus between 90-45 Ma) whereas the reconstruction of Zahirovic et al. (2016) suggest only a 10 Myr long hiatus with subduction initiating after 62 Ma (hiatus ~75–62 Ma). Nonetheless, the SZI event might have restarted subduction along the temporarily distinct destructive boundary by an episodic SZI mechanism. The general northward motion of the Indo-Australian plate driven by the surrounding northward directed subduction zones might have induced significant North-South directed compression and thereby fostered the new subduction zone. It is, however, also possible that the subduction zone re-initiated by a lateral progression of still active surrounding subduction systems.

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
  • Seismic tomography VoteMap included
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Philippine subduction zone initiation

The present-day Philippine subduction zone is thought to have started at about 9 Ma via a subduction polarity flip.

Schematic tectonic reconstruction of the Philippine SZI event (modified from Hall, 1996 and Wu et al., 2016). The collision of the Palawan continental block with the trench of the east-dipping subduction of the Eurasia plate below the Philippine Sea Plate is suggested to have caused a flip in subduction polarity, initiating the new Philippine subduction zone. Shown are the new subduction zone (pink line) and other active (solid purple lines) and inactive (dashed purple lines) subduction zones.

The present-day Philippine subduction zone, with the Philippine Sea plate subducting below the Eurasian plate, is thought to have started at about 9 Ma (e.g., Wu et al., 2016), after the collision of the Palawan continental block with the Philippine Mobile Belt (PMB) that occurred around 20–11 Ma (Marchadier and Rangin, 1990; Yumul Jr. et al., 2003).

The Palawan block belongs to the Eurasian plate and drifted towards the southeast until it collided with the Philippine archipelago at the trench of the former, eastward subduction zone (Marchadier and Rangin, 1990). This collision likely induced a flip in subduction polarity, which initiated the westward Philippine subduction zone (Barrier et al., 1991) on the other side of the already existing volcanic arc.

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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Cascadia subduction zone initiation

The Cascadia subduction zone initiation event formed at around 53–43 Ma likely as an episodic subduction via a trench jump after the large igneous province (LIP) Siletzia accreted.

Schematic tectonic reconstruction of the Cascadia SZI event (modified from Stern and Dumitru et al., 2019 and Wells et al., 2014). A trench jump occurred due to the accretion of the Siletzia and Yakutat large igneous province (LIP) formed by the Yellowstone plume, initiating the new Cascadia 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 Cascadia subduction zone initiation (SZI) event formed the currently active Cascadia subduction zone at around 53–43 Ma (Hyndman et al., 1990; Priest, 1990; Schmandt and Humphreys, 2011; Stern and Dumitru, 2019) and induced subduction of the Farallon and Kula plates below the North America plate.

The Cascadia SZI event is believed to have occurred as an episodic subduction via a trench jump after the large igneous province (LIP) Siletzia accreted at the previous trench of the Farallon/Cordilleran subduction zone (Wells et al., 2014; Stern and Dumitru, 2019). There is also an indication of the presence of the prominent Yellowstone mantle plume during the time of the onset, which might have been facilitated by the breaking of the intact subducting plate (Stern and Dumitru, 2019). It is worth noting that at the time of the trench jump there was ongoing subduction to the north and south of the Cascadia subduction zone. Although the accretion of the Siletzia block is likely to be the main cause of the trench jump, the nearby subduction zones in the north and south might therefore also have had a role in this SZI event.

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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South Sandwich subduction zone initiation

The South Sandwich SZI event is estimated to have occurred between 39 and 29 Ma as a new destructive boundary.

Schematic tectonic reconstruction of the South Sandwich SZI event (modified from Dalziel et al., 2013b). The arrival of the Chile ridge at the South America trench might have triggered a flip in subduction polarity, but the South Sandwich subduction zone is suggested to have initiated as a newly destructive boundary. Shown are the new subduction zone (pink line), other active subduction zones (solid purple lines), spreading ridges (solid red lines), and transform faults (red dashed lines).

The South Sandwich SZI event marked the start of the subduction of the South American plate westwards beneath the Scotia plate, giving rise to the South Sandwich subduction zone that remains active at present-day. The age of that SZI event remains debated, with estimates ranging from ~30 Ma to the Cretaceous (Eagles, 2010; Pearce et al., 2014) and, from the cross-disciplinary perspective, we estimate SZI to have occurred between 39 and 29 Ma. The type of SZI associated with the onset of South Sandwich subduction is interpreted as a new destructive boundary (after e.g., Pearce et al., 2014). South Sandwich subduction has, however, also been attributed to lateral propagation from the Endurance Collision Zone (Eagles, 2010) – in which case the event would not actually qualify as SZI, according to our definition. More broadly (on a larger scale), the South Sandwich SZI might be a consequence of subduction polarity reversal (Crameri and Tackley, 2014). In this interpretation, the South Sandwich SZI occurred as a subduction polarity reversal further back in time (between around 80-40 Ma) along one section of the previously intact South America-South Shetland subduction system (Crameri and Tackley, 2014), possibly by collision of the Chile ridge with the preexisting subduction trench (Barker, 2001). The South Sandwich SZI event might have coincided with a reconstructed acceleration of westward motion of the South America plate relative to the Africa plate (Barker 2001).

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
  • Seismic tomography VoteMap included
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Ryukyu subduction zone initiation

The Ryukyu SZI event reinitiated subduction of the Philippine Sea plate below the Eurasian plate through episodic subduction at around 6 Ma.

Schematic tectonic reconstruction of the Ryukyu SZI event (modified from Faccenna et al., 2018). A slab break-off event caused a pause in arc activity. Subduction of the Philippine Sea plate started again along the same margin, initiating the new Ryukyu 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 Ryukyu SZI event reinitiated subduction of the Philippine Sea plate below the Eurasian plate, and is presently characterised by a northwest-dipping slab along the western boundary of the Philippine Sea plate. For Ryukyu, there seem to be two SZI events to consider, an older more enigmatic event and a subsequent, younger one. The first, older SZI event is unclear, as reconstruction models currently disagree (e.g., Faccenna et al., 2018 versus Müller et al. 2016) and geologic evidence is largely missing. The second, younger SZI event, which is considered and named here Ryukyu SZI event, might be classified as an episodic SZI event that occurred at around 6 Ma. The two separated phases of ongoing subduction are interrupted by a slab break-off event (Lallemand et al. 2001; Malavieille et al. 2002), due to the arrival of the Gagua Ridge at the subduction trench (Deschamps and Lallemand, 2002).

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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Glendonite formation (Fur)

Model for the formation of glendonite (and concretionary calcite growth around them) in the Eocene-aged sediments of northern Denmark.

Model for the formation of glendonite (and concretionary calcite growth around them) in the Eocene-aged sediments of northern Denmark. This model is modified from that proposed by Vickers et al. (2020) based on geochemical and visual observations of the glendonites of the Fur Formation, and previous studies of ikaite and glendonite (as described in Vickers et al., 2020).

This figure was encouraged by iEarth 2022 seed funds.

  • Creator: Madeleine L. Vickers
  • This version: 14.11.2022
  • License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
  • Specific citation: This graphic by Madeleine L. Vickers from Vickers et al. (2020) is available via the open-access s-Ink.org repository.
  • Related reference: Vickers, M.L., Lengger, S.K., Bernasconi, S.M., Thibault, N., Schultz, B.P., Fernandez, A., Ullmann, C.V., McCormack, P., Bjerrum, C.J., Rasmussen, J.A. and Hougård, I.W., 2020. Cold spells in the Nordic Seas during the early Eocene Greenhouse. Nature communications, 11(1), pp.1-12. DOI: https://doi.org/10.1038/s41467-020-18558-7
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