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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