Tseax Cone (/ˈsiːæks/ SEE-aks) is a small volcano in the Nass Ranges of the Hazelton Mountains in northwestern British Columbia, Canada.

[14] The well-established local name for the volcano, Tseax Cone, became official on December 13, 1991, and was adopted on the National Topographic System map 103P/2.

[2][8] To the Nisga'a people, Tseax Cone is known as Wil Ksi Baxhl Mihl; in their language it means 'Where the Fire Ran Out', which is a reference to the volcanic eruption that sent lava spewing out of the volcano.

Much of this Pacific air enters via the Skeena River valley or flows over the Kitimat Ranges, resulting in cloud cover and heavy rain.

[21] Large stretches of continuous mosses and lichens give the illusion that the lava flows are carpeted in fur; grasses and smaller shrubs are only present in very small quantities.

[21] However, this may change by the end of the 21st century as lodgepole pine and cottonwood forests continue to develop on the lava flows in an increasingly wetter and milder climate.

[10] This is a broad area of shield volcanoes, lava domes, cinder cones and stratovolcanoes extending from northwestern British Columbia northwards through Yukon into easternmost Alaska.

[27] The dominant rocks comprising these volcanoes are alkali basalts and hawaiites, but nephelinite, basanite and peralkaline[a] phonolite, trachyte and comendite are locally abundant.

[35] All of the products erupted from Tseax Cone are rich in iron-titanium oxides and were produced by low partial melting 55–62 kilometres (34–39 miles) below the surface in the upper crust.

[50] Their disruption of the existing drainage system resulted in the formation of new channel planforms and geomorphic features such as lava-dammed lakes, alluvial fan blockages and an inversion of topographic relief.

[57] Reports of the rich oral history of the local Nisga'a people by missionaries as early as the 1910s suggest that Tseax Cone was erupting around 1770.

G. Hanson wrote in a 1923 Canada Department of Mines report that 170-year-old trees were found growing on lava from Tseax Cone; this would indicate an eruption prior to 1753.

In 1935, Marius Barbeau concluded in the Canadian Geographical Journal that the latest eruption at Tseax Cone occurred in the late 18th century.

Akrigg speculated in British Columbia Chronicle, 1847–1871: Gold & Colonists that the Tseax Cone eruption was witnessed by naval officer Juan Francisco de la Bodega y Quadra on August 24, 1775.

However, this is extremely unlikely because Bodega y Quadra's schooner, the Sonora, was anchored more than 280 kilometres (170 miles) west of Tseax Cone across mountainous terrain.

[59] Michael D. Higgins proposed in a 2008 Journal of Volcanology and Geothermal Research article that the 1700 Cascadia earthquake may have caused the latest Tseax Cone eruption by destabilizing a subterranean magmatic system.

A lava-encased cottonwood near the Nass River was reported by Sutherland Brown in 1969 and Jack Souther in 1970 to have yielded a radiocarbon date of 220 ± 130 years.

[69] A charred tree trunk found standing in the vertical wall of the spatter rampart also yielded a radiocarbon date of 625 ± 70 years.

[71] The question of whether Tseax Cone formed during one or more distinct eruptive episodes has important implications for future activity and hazard mitigation efforts.

[72] If Tseax Cone is polygenetic, future activity could produce lava flows and potentially block local streams as happened previously.

Carbon dioxide emissions from Tseax Cone could pose a threat to local inhabitants due to the gas's ability to replace oxygen in low-lying areas and poorly ventilated structures.

Another potential hazard relating to future activity from Tseax Cone is the ignition of wildfires by eruptions since the area contains vegetation.

[59] According to Nisga'a legends, the Tseax Cone eruption caused the deaths of 2,000 people and the destruction of at least three villages on the banks of the Nass River.

It started from the river where the people fished salmon, away up there, and ran down to the place where the canyon now is...[59]The "poisonous smoke" mentioned in Barbeau's report may have been odourless carbon dioxide.

Interaction of the lava flow with the Nass River may have produced dense clouds of vaporized water mixed with volcanic gases such as carbon dioxide and hydrogen sulfide.

The average discharge rate of the Nass River is strong enough to drown anyone attempting to escape by swimming during the summer months of June, August and September; Tseax Cone is suspected to have erupted during this time.

[77] The Nisga'a also recall the disruption of the Tseax River, stating that "before the volcanic eruption, when our people lived here at Wii Lax K'ap, there was a stream close by where salmon spawned.

[74] Pleas for protection of the Tseax Cone lava flows date back to at least 1972 when forestry operations had left tree stumps and debris on their surfaces.

An alternative route to the lava flows involves travelling the paved Stewart–Cassiar Highway north of Kitwanga for 78 kilometres (48 miles) to the Cranberry River.

[25] From there, the unpaved Nass Forest Service Road extends 86 kilometres (53 miles) southwest to Gitlaxt'aamiks which lies on the northeastern edge of the lava flows.