Cascade Volcanic Arc calderas

The Cascade Volcanic Arc is a chain of volcanoes stretching from southern British Columbia down to northern California. Within the arc there is a variety of stratovolcanoes like Mount Rainier and broad shield volcanoes like Medicine Lake. But calderas are very rare in the Cascades, with very few forming over the 39 million[1] year lifespan of the arc.

The few eruptions that do form calderas rarely make it into the VEI 7 range, staying confined to the VEI 6 range in most cases. The only volcanoes known to have produced eruptions within the VEI 7 range are Crater Lake, the Mt. Baker Volcanic Field, and the Lassen Volcanic Center.

All of the exceptionally large caldera-forming eruptions within the cascades erupted silica-rich magmas, with the three VEI 7s erupting mainly rhyodacite and rhyolite.

Crater Lake, the most recent caldera to form in the Cascades Kulshan Caldera's intracaldera ignimbrite deposit near Upper Swift Creek in the northwestern Mount Baker volcanic field, Washington.

## List of calderas

[edit]

Volcano  | Caldera Name  | Caldera Size  | Age  | Eruption Unit Name  | Magma Volume (km3) | Tephra Volume (km3)  | VEI  | Notes  | Reference(s)

|
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|
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Silverthrone | Silverthrone caldera  | 20 km wide  | <1,100,000  | N/A  | N/A  | N/A  |  | Poorly studied  | [2]
Franklin Glacier Complex | N/A  | 6 x 20 km  | <6,800,000  | N/A  | N/A  | N/A  |  | Poorly studied  | [3]
Coquihalla Volcanic Complex | N/A  | 6 x 6 km  | <21,400,000  | N/A  | N/A  | 50  |  | Tephra volume does not represent

a single eruption

| [4][5]
Hannegan | Hannegan caldera  | 8 x 3.5 km  | 3,722,000  | Ignimbrite of Hannegan Peak  | N/A  | N/A  | 6-7  | Trap-door caldera, first collapse. Both ignimbrites have a combined magma volume of 127 km3 | [6]
|  |  | 3,720,000  | Ignimbrite of Ruth Mountain  | N/A  | N/A  | 6-7  | Trap-door caldera, second collapse  | [6]
Big Bosom Buttes | Big Bosom caldera  | 4 x 5 km ?  | Oligocene | N/A  | N/A  | N/A  |  | Poorly studied  | [6]
Mount Rahm ?  | Mount Rahm caldera  | N/A  | Oligocene  | N/A  | N/A  | N/A  |  | Poorly studied  | [6]
Mount Baker Volcanic Field  | Kulshan Caldera | 4.5 x 8 km  | 1,149,000  | Lake Tapps tephra  | 124  | N/A  | 7  |  | [7][8]
Gamma Ridge ?  | Gamma Ridge caldera | N/A  | 1,242,000  | N/A  | 40  | N/A  | 6-7  | Poorly studied, trap-door caldera  | [9]
Mount Aix Volcanic Complex | Mount Aix caldera  | 6 x 9  | 28,000,000  | Bumping River tuff-north  | N/A  | N/A  | 6-7  | Cummalitave volume of Mt. Aix tuffs

exceeds 100 km3

| [10][6]
|  |  | 25,000,000  | Bumping River tuff-east  | N/A  | N/A  | 6-7  |  | [10]
|  |  | 25,000,000  | Cash Prairie tuffs  | N/A  | N/A  | 6-7  |  | [10]
Goat Rocks | Devils Horns caldera  | 5 x 8 km  | 3,200,000  | N/A  | N/A  | >60  | 6  | Tephra volume may represent

multiple eruptions

| [11][6]
Newberry | Newberry Crater  | 6.4 x 8 km  | 80,000  | Olema ash  | 14-22  | N/A  | 6  | Second caldera formation  | [9]
|  |  | 230,000  | Tepee Draw tuff  | 10  | 25  | 6  | First caldera formation  | [12][9]
Mount Mazama | Crater Lake  | 8 x 10 km  | 5783 BCE  | Mazama ash  | 61  | 176  | 7  | Largest Holocene eruption in the arc  | [13][14][12]
|  |  | 29,900  | Trego Hot Springs  | 8  | 20.8  | 6  |  | [15][12]
Medicine Lake  | Medicine Lake caldera  | 7 x 12 km  | 171,000  | Antelope Well tuff  | 20  | N/A  | 6  |  | [9]
Lassen Volcanic Center  | Rockland caldera  | N/A  | 610,000  | Rockland tephra  | 130  | 326.7  | 7  |  | [15][12]

## Places where calderas could be

[edit]

These are places that have experienced very large eruptions of ash and ignimbrite that reached a VEI of 6 or greater, but have no documented calderas.

### Tumalo Volcanic Center

[edit]

The Tumalo Volcanic Center is a volcano located just east of Bend, Oregon. It started producing large eruptions around 650,000 years ago, with its first eruption reaching a 5 on the VEI scale and erupting more than 1 km3 of magma.[12] The volcano would go on to produce at least three more voluminous eruptions. The two largest eruptions ejected more than 5 km3 of magma.[12] Eruptions of those sizes usually entail caldera collapses.[16] However no calderas have been identified in this area.

### Deschutes Formation

[edit]

Between 6.25 and 5.45 million years ago the cascade volcanic arc flared up in activity.[16] Producing far more explosive ignimbrite eruptions than usual. The activity was mostly focused within the central Oregon cascades. Over 78 individual eruptions have been identified and the total volume of pyroclastic products in the Deschutes formation is estimated to be between 400 and 675 km3.[17]

## References

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1. ^ "The Restless Northwest | WSU Press | Washington State University". Retrieved 29 December 2022.
2. ^ "Global Volcanism Program | Silverthrone". Smithsonian Institution | Global Volcanism Program. Retrieved 29 December 2022.
3. ^ Gabrielse, H.; Yorath, C. J. (1 January 1991). Geology of the Cordilleran Orogen in Canada. Geological Society of America. ISBN 978-0-8137-5454-3.
4. ^ Berman, Robert G. (August 1980). "The Coquihalla volcanic complex, Southwestern British Columbia". Canadian Journal of Earth Sciences. 17 (8). doi:10.1139/e80-099. OCLC 753418694.
5. ^ Berman, Robert G.; Armstrong, Richard Lee (8 February 2011). "Geology of the Coquihalla Volcanic Complex, southwestern British Columbia". Canadian Journal of Earth Sciences. 17 (8): 985–995\. doi:10.1139/e80-099.
6. ^ a b c d e f Tucker, David S.; Hildreth, Wes; Ullrich, Tom; Friedman, Richard M. (2007). "Geology and complex collapse mechanisms of the 3.72 Ma Hannegan caldera, North Cascades, Washington, USA". Geological Society of America Bulletin. 119 (3–4): 14. Bibcode:2007GSAB..119..329T. doi:10.1130/B25904.1.3–4&rft.pages=14&rft.date=2007&rft_id=info:doi/10.1130/B25904.1&rft_id=info:bibcode/2007GSAB..119..329T&rft.aulast=Tucker&rft.aufirst=David+S.&rft.au=Hildreth,+Wes&rft.au=Ullrich,+Tom&rft.au=Friedman,+Richard+M.&rft_id=http://pubs.er.usgs.gov/publication/70032860&rfr_id=info:sid/en.wikipedia.org:Cascade+Volcanic+Arc+calderas" class="Z3988">
7. ^ King, Georgina E.; Pearce, Nicholas J. G.; Roberts, Helen M.; Smith, Victoria C.; Westgate, John A.; Gaylord, David R.; Sweeney, Mark R. (September 2016). "Identification of a Kulshan caldera correlative tephra in the Palouse loess of Washington State, northwest USA". Quaternary Research. 86 (2): 232–241\. Bibcode:2016QuRes..86..232K. doi:10.1016/j.yqres.2016.06.004. hdl:2160/43910. ISSN 0033-5894. S2CID 132977164.
8. ^ Hildreth, Wes; Lanphere, Marvin A.; Champion, Duane E.; Fierstein, Judy (29 February 2004). "Rhyodacites of Kulshan caldera, North Cascades of Washington: Postcaldera lavas that span the Jaramillo". Journal of Volcanology and Geothermal Research. 130 (3): 227–264\. Bibcode:2004JVGR..130..227H. doi:10.1016/S0377-0273(03)00290-7. ISSN 0377-0273.
9. ^ a b c d Nathenson, Manuel; Clynne, Michael A.; Muffler, L.J. Patrick (2012). "Eruption probabilities for the Lassen Volcanic Center and regional volcanism, northern California, and probabilities for large explosive eruptions in the Cascade Range". Scientific Investigations Report: 12. Bibcode:2012usgs.rept...12N. doi:10.3133/sir20125176b. ISSN 2328-0328.
10. ^ a b c King, John (24 May 1994). "Magmatic Evolution and Eruptive History of the Granitic Bumping Lake Pluton, Washington: Source of the Bumping River and Cash Prairie Tuffs". Dissertations and Theses. doi:10.15760/etd.6649.
11. ^ Hildreth, Wes (2007). Quaternary Magmatism in the Cascades: Geologic Perspectives. U.S. Geological Survey. ISBN 978-1-4113-1945-5. OCLC 444477580.
12. ^ a b c d e f "VOGRIPA - Home". www2.bgs.ac.uk. Retrieved 29 December 2022.
13. ^ Buckland, Hannah M.; Cashman, Katharine V.; Engwell, Samantha L.; Rust, Alison C. (6 February 2020). "Sources of uncertainty in the Mazama isopachs and the implications for interpreting distal tephra deposits from large magnitude eruptions". Bulletin of Volcanology. 82 (3): 23. Bibcode:2020BVol...82...23B. doi:10.1007/s00445-020-1362-1. hdl:1983/7066de89-c67e-4dc8-8c33-335fb23d5f9c. ISSN 1432-0819. S2CID 211038738.
14. ^ "Global Volcanism Program | Crater Lake". Smithsonian Institution | Global Volcanism Program. Retrieved 29 December 2022.
15. ^ a b Yang, Qingyuan; Bursik, Marcus; Pitman, E. Bruce (13 August 2019). "A new method to identify the source vent location of tephra fall deposits: development, testing, and application to key Quaternary eruptions of Western North America". Bulletin of Volcanology. 81 (9): 51. arXiv:1806.02882. Bibcode:2019BVol...81...51Y. doi:10.1007/s00445-019-1310-0. ISSN 1432-0819. S2CID 199541722.
16. ^ a b Pitcher, Bradley W.; Kent, Adam J. R.; Grunder, Anita L.; Duncan, Robert A. (1 June 2017). "Frequency and volumes of ignimbrite eruptions following the Late Neogene initiation of the Central Oregon High Cascades". Journal of Volcanology and Geothermal Research. 339: 1–22\. Bibcode:2017JVGR..339....1P. doi:10.1016/j.jvolgeores.2017.04.019. ISSN 0377-0273.
17. ^ Pitcher, Bradley W.; Kent, Adam J. R.; Grunder, Anita L. (1 April 2021). "Tephrochronology of North America's most recent arc-sourced ignimbrite flare-up: The Deschutes Formation of the Central Oregon Cascades". Journal of Volcanology and Geothermal Research. 412: 107193. Bibcode:2021JVGR..41207193P. doi:10.1016/j.jvolgeores.2021.107193. ISSN 0377-0273. S2CID 234042444.