Physical volcanology of Tseax Volcano, British Columbia, Canada

Abstract

Tseax volcano erupted ∼ 250 years ago in NW British Columbia, Canada producing tephra deposits and lava flows. Field mapping has defined the stratigraphy of Tseax and the lava flow morphologies. Aerial photogrammetry and bathymetry surveys were used to create a high resolution digital elevation model of the volcano to facilitate mapping and estimates of erupted material volumes. Tseax volcano (∼ 10.4 ± 0.7 × 10 6 m 3 ) comprises an outer breached spatter rampart and an inner conical tephra cone. Tseax is associated with a 32 km long and 0.49 ± 0.08 km 3 basanite-to-tephrite lava flow field covering ∼ 36 km 2 and divided into 4 distinct lava flows with heterogeneous surface morphologies. We present a volcanological map of Tseax volcano at a scale of 1:22,500. This will serve as supporting information for further research on the eruptive history of Tseax volcano and the lava flow field emplacement.

Inflated pyroclasts in proximal fallout deposits reveal abrupt transitions in eruption behaviour

“…The tephra cone and valley-filling lavas overlay intercalated sandstone to siltstone and mudstone from the late Jurassic Bowser Lake group 49 , 50 . Detailed volcanological mapping shows that Tseax volcano consists of a ~65 m high, 350-400 m diameter tephra cone (2.8 ± 0.4 × 10 6 m 3 ) situated within a 550-600 m diameter oxidised horseshoe-shaped spatter rampart 44 . Another smaller (~20 m high, ~55 m diameter, 1.7 ± 0.1 ×10 4 m 3 ) highly oxidised tephra cone, unnamed but referred to here as Satellite cone, is located 470 m to the north of Tseax and in close proximity to a group of small tephra mounds 44 (Fig.…”

“…Red contours denote tephra deposit thickness. Modified after Le Moigne et al 44 . d Oblique 3D view of Tseax and surrounding area generated by digital photogrammetry.…”

“…d Oblique 3D view of Tseax and surrounding area generated by digital photogrammetry. Modified after Le Moigne et al 44 . …”

Chronology and Eruption Dynamics of the Historic∼1700 CE Eruption of Tseax Volcano, British Columbia, Canada

“…and far-travelled lava flows (Sutherland Brown, 1969;Le Moigne et al, 2020). The eruption was recorded in the Adaawak (traditional oral histories) of the Nisga'a First Nation as they were significantly impacted with potentially up to 2,000 fatalities in three destroyed villages (Collison and Seeley, 1915;McCullagh, 1918;Hanson, 1924;Barbeau, 1935;Nisga'a Tribal Council, 2004;Williams-Jones et al, 2020), making it Canada's deadliest volcanic event (Hickson and Edwards, 2001).…”

“…Despite a rich oral history, the exact sequence and timing of the volcanic events has been difficult to establish. Furthermore, only a relatively limited number of scientific studies have been made on Tseax volcano including dating (Symons, 1975;Wuorinen, 1978;Williams-Jones et al, 2020), physical mapping (Hanson, 1924;Sutherland Brown, 1969;Le Moigne et al, 2020) and geochemistry studies (Higgins, 2009;Gallo, 2018;Le Moigne et al, 2022).…”