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Tag: Subduction initiation

Subduction initiation is explained in this collection of accurate, accessible science graphics, designed to make understanding this key geological process clear and engaging. These visuals explore how and where subduction zones first form, triggering the descent of one tectonic plate beneath another and setting the stage for earthquakes, volcanic arcs, and mountain building. Perfect for educators, students, and geology enthusiasts, this subduction initiation graphic collection turns complex geodynamic concepts into visually rich, easy-to-grasp resources for teaching and learning.

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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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
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Anatolia subduction zone initiation

The Anatolia subduction zone (or ‘Anatolian Neotethys’) started at around 104 Ma as a consequence of fracture zone inversion.

Schematic tectonic reconstruction of the Anatolia subduction zone initiation event (modified from van Hinsbergen et al., 2019a,b). Shown are the new subduction zone (pink line), other active subduction zones (solid purple lines), and transform faults (red dashed lines).

The Anatolia subduction zone (also referred to as ‘Anatolian Neotethys’ or ‘southern strand of the Neotethys’) started at around 104 Ma. It initiated within the oceanic lithosphere of the Neotethys and, together with the Oman SZI event, represents the western Neotethyan subduction system. SZI has been proposed to be the consequence of fracture zone inversion (van Hinsbergen et al., 2019a, Maffione et al., 2017), though this remains a matter of debate (Agard et al., 2007; van Hinsbergen et al., 2019a).

At the time of SZI, both downgoing and overriding plates were oceanic lithosphere of the Neotethys, the overriding oceanic lithosphere has also been termed ‘Anadolu plate’ (Gürer et al., 2016). The final stages of subduction of the downgoing plate saw the arrival and accretion of continental lithosphere (the Africa-Arabia plate), including several microcontinents of ‘Greater Adria’ (Gaina et al., 2015; van Hinsbergen et al., 2019b).

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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Oman subduction zone initiation

The Oman subduction zone, together with the Anatolian subduction zone, started at around 104 Ma as a consequence of fracture zone inversion.

Schematic tectonic reconstruction of the Oman SZI event (modified from van Hinsbergen et al., 2019a,b). Shown are the new subduction zone (pink line), other active subduction zones (solid purple lines), and transform faults (red dashed lines).

The Oman subduction zone, together with the Anatolian subduction zone, formed the Western Neotethyan subduction system. The Oman SZI event was widely thought to have initiated along, or in the vicinity of, a Neotethyan mid-oceanic ridge (e.g., Boudier et al. 1988; Nicolas et al., 2000; Duretz et al., 2016). Recently, it has been suggested that the subduction zone initiated along a fracture zone, located parallel to the Arabian continent (van Hinsbergen et al., 2019a; Maffione et al., 2017).

The subduction zone seems to have initiated at 104 Ma (e.g., Guilmette et al., 2018) within Neotethyan oceanic lithosphere, similar to the Anatolia SZI (see Anatolia SZI event in the SZI database), but with the opposite vergence (van Hinsbergen et al., 2019a). At the time of SZI, both the downgoing and overriding plates were oceanic lithosphere of the Neotethys. In the case of Oman (and in contrast to the Anatolian subduction zone), the ‘Anadolu plate’ (Gürer et al., 2016) subducted below the Africa-Arabia continental plate (i.e., ‘Greater Adria’ of Gaina et al., 2015 and van Hinsbergen et al., 2019a,b). The subduction zone later terminated and resulted in widespread ophiolite obduction onto the Arabian continental margin in the Late Cretaceous at 70 ± 5 Ma, represented by the Semail ophiolite of Oman, the Kermanshah and Neyriz ophiolites of Iran, the Baer Bassit ophiolite of Syria, the Hatay ophiolites of SE Turkey, and the Troodos ophiolite of Cyprus (Koop and Stoneley, 1982; Searle and Cox, 1999; Nicolas et al., 2000; Al-Riyami et al., 2002; Searle et al., 2004; Dilek and Furnes, 2009; Homke et al., 2009; Agard et al., 2011).

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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New Hebrides-New Britain subduction zone initiation

The New Hebrides-New Britain (NHNB) SZI event evolved into the New Hebrides, San Cristobal, and New Britain trenches by subduction polarity reversal at around 10 Ma.

Schematic tectonic reconstruction of the New Hebrides-New Britain SZI event (modified from Schellart et al., 2006 and Holm et al., 2016). The collision of the Ontong Java plateau with the trench of the Melanesian subduction zone is suggested to have caused a flip in subduction polarity, initiating the New Hebrides-New Britain subduction zone. Shown are the new subduction zone (pink line) and other active (solid purple lines) and inactive (dashed purple lines) subduction zones.

The New Hebrides – New Britain (NHNB) SZI event evolved into the present-day subduction system that includes the New Hebrides, San Cristobal, and New Britain trenches. The Australian plate currently subducts below a former portion of itself, lying to the north-east, that today makes up the North Fiji Basin (e.g. Schellart et al., 2006). These trenches are all currently connected to each other and initiated at similar times, which is why their onset is here attributed to one single event.

It has been suggested that the onset of the NHNB subduction zone, which is related to subduction of the Australian plate below the Pacific plate, originated by a reversal in subduction polarity at around 10 Ma. While some studies favour a time period for the SZI event between 10 and 6 Ma (Chase, 1971; Auzende et al., 1988), others suggest an onset age of between 14–11 Ma (Greene et al., 1994; Schellart et al., 2006). This polarity reversal likely occurred as a result of the collision of the Ontong Java plateau with the Vitiaz trench (e.g. Greene et al., 1994; Holm et al. 2013). The Ontong Java plateau lies on the Pacific plate that was subducting below the Australian plate during the collision, prior to the polarity reversal.

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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Lesser Antilles subduction zone initiation

The Lesser Antilles SZI event that formed the present-day Lesser Antilles subduction zone likely occurred between 59–38 Ma and might be an episodic event.

Schematic tectonic reconstruction of the Lesser Antilles SZI event (modified from van Benthem et al., 2013 and Boschman et al., 2014). Subduction of the North and South America plates beneath the Caribbean plate was probably already active earlier on. At 58–39 Ma, subduction jumped eastwards, creating the new Lesser Antilles subduction zone. Shown are the new subduction zone (pink line), other active (solid purple lines) and inactive (dashed purple lines) subduction zones, and transform faults (red dashed lines).

The Lesser Antilles SZI event that formed the present-day Lesser Antilles subduction zone likely occurred between 59–38 Ma (Boschmann et al., 2014), with the North and South American plates subducting below the Caribbean plate. However, there is a debate on the nature of this event, which also represents the transition from the Greater Caribbean Arc to the Lesser Antilles subduction zone. The break in the slab, revealed by seismic tomography (van Benthem et al., 2013), along with the age gap between the Aves Ridge and the Lesser Antilles Arc and the start of the formation of the Barbados Accretionary Prism (Boschman 2014) suggests episodic subduction. Other interpretations consider continuous subduction during the narrowing of the arc and suggest that the arc has jumped 50–250 km from the Avis ridge to the Lesser-Antilles arc during continuous subduction roll-back and the consequent opening of the Grenada and Tobago basins (together) as a forearc basin (e.g., Aitken et al., 2011). Due to the widening forearc, the Avis ridge became inactive. In this scenario, the SZI event of the Lesser Antilles is the same as that of the Greater Caribbean arc, which might have happened sometimes between 120 to 88 Ma. This earlier event is not considered here any further.

The Lesser Antilles SZI event might be an episodic event that followed from a previously active, but subsequently extinct, subduction zone; it is suggested that the active arc from the Aves ridge transitioned to, and formed, the Lesser Antilles arc during the mentioned time span (Boschmann et al., 2014).

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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Izu-Bonin-Mariana subduction zone initiation

The onset of the Izu-Bonin-Mariana (IBM) subduction zone likely occurred at around 52 Ma likely along a pre-existing fracture zone after a plate reorganisation.

Schematic tectonic reconstruction of the Izu-Bonin-Mariana SZI event (modified from Lallemand, 2016). A plate reorganisation, possibly due to the arrival of the Izanagi ridge at the trench, is suggested to trigger SZI along a pre-existing transform fault in the south, initiating the Izu-Bonin-Mariana subduction zone. The orange circle shows the location of the Oki-Daito plume. 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 onset of the presently active Izu-Bonin-Mariana (IBM) subduction zone likely occurred at around 52 Ma with the subduction of the Pacific plate under the Proto-Philippine Sea plate, which was mostly formed of arc terranes at the time of subduction initiation (e.g., Ishizuka et al., 2018). The age of this SZI event is mostly based on the age of the oldest Early basalts (e.g., Reagan et al., 2019), which are considered to be the first magmatic product of SZI and to erupt very soon after the onset of subduction.

The most common view is that subduction initiated along a pre-existing fracture zone after a plate reorganisation due to the subduction of the Izanagi-Pacific ridge beneath Asia at around 60–55 Ma (O’Connor et al., 2013; Lallemand, 2016) or the collision of the Olutorsky arc (Domeier et al., 2017). Regardless of the cause, these stress changes might have caused compression across a transform fault (or a pre-existing fracture zone) and locally initiated subduction (Hall et al., 2003). Additionally, ocean-island basalt (OIB) magmatism in the West Philippine basin indicates the presence of a mantle plume (the Oki-Daito plume) that started its activity almost at the same time as the IBM SZI (Ishizuka et al., 2013).

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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Puysegur trench formation

A schematic highlighting the formation of the Puysegur trench, New Zealand, where subduction zone initiation may be both horizontally and then vertically driven, according to a 4D evolution model of this margin.

A schematic highlighting the formation of the Puysegur trench, New Zealand, where subduction zone initiation may be both horizontally and then vertically driven, according to a 4D evolution model of this margin. Its gradual evolution from north to south represents a pseudo-temporal sequence of a forming subduction zone, which naturally spans a few millions of years. In the northern segment, where subduction nucleated, horizontal forces may have dominated, representative of the early stages of subduction initiation. With time, vertical forces took over, propagating along the evolving megathrust and helping to finally form a self-sustaining subduction zone.

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Subduction zone initiation types

Illustration of the three types of subduction zone initiation (SZI) events, namely Newly destructive, Episodic subduction, and Polarity reversal.

Illustration of the three types of subduction zone initiation (SZI) events. As outlined in Crameri et al. (2020), the SZI type is either Newly destructive (a subduction fault establishing from an intact-plate portion or some sort of non-subduction-related plate weakness), Episodic subduction (a subduction fault establishing at the same location following a previous, yet terminated subduction zone with the same polarity), or Polarity reversal (formation of a new subduction fault with opposite polarity to the fault of the pre-existing, terminating subduction zone).

  • Creator: Fabio Crameri
  • This version: 24.10.2021
  • License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
  • Specific citation: This graphic by Fabio Crameri from Crameri et al. (2020) is available via the open-access s-Ink 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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