Tseax Cone ( SEE-aks) is a small volcano in the Nass Ranges of the Hazelton Mountains in northwestern British Columbia, Canada. It has an elevation of 609 metres (1,998 feet) and lies within an east–west valley through which a tributary of the Tseax River flows. The volcano consists of two nested structures and was the source of four lava flows that descended into neighbouring valleys. A secondary eruptive centre lies just north of Tseax Cone on the opposite side of Melita Lake. It probably formed simultaneously with Tseax Cone, but the timing of volcanism at the two eruptive centres is not precisely known; both were formed by volcanic activity sometime in the last 800 years. The exact timing of volcanism at Tseax Cone has been a subject of controversy because there are no direct written accounts; radiocarbon dating of plants killed by lava or ejecta from the volcano has yielded ages as old as 625 ± 70 years to as young as 190 ± 15 years. There is also controversy over whether the volcano was formed during one or more distinct episodes of eruptive activity. The single eruptive episode hypothesis has been proposed by researchers as early as 1923 whereas a multi-eruption hypothesis was proposed in 1978. Most research suggests that Tseax Cone was formed during one episode of eruptive activity; new data supporting this hypothesis was reported in 2020. Tseax Cone is the subject of legends told by the local indigenous people. They describe the destruction of villages along the Nass River by the volcano and the death of several people from inhaling volcanic fumes, although other causes of death may have been involved. As many as 2,000 people are claimed to have been killed by an eruption from Tseax Cone; this would make it the deadliest geological disaster in Canada and the second-worst natural disaster in Canadian history by death toll. Tseax Cone has therefore been described as the deadliest volcano in Canada. Renewed eruptions from the volcano could start wildfires and block local streams with lava flows. Tseax Cone lies within an ecoregion characterized by mountainous terrain and several streams. Rainforests occur at the volcano, as well as numerous species of mammals. Lichens and mosses cover most of the lava flows that have issued from Tseax Cone, although rainforests and waterbodies also obscure them. After at least 20 years of pleas for protection, the volcano and lava flows were established as Nisga'a Memorial Lava Bed Provincial Park in 1992. Tseax Cone and its lava flows can be accessed via provincial highways and backcountry roads.
Names and etymology Tseax Cone has been variously called Aiyansh Volcano, Aiyansh River Volcano, Tseax River Cone and Tseax Volcano. Aiyansh comes from a Nisga'a word meaning 'leafing early' or 'early leaves', whereas Tseax comes from a Nisga'a word meaning 'new water'. Tseax is possibly a reference to the disturbed drainage patterns of the Tseax River caused by a volcanic eruption from the cone. 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. To the local Nisga'a people, Tseax Cone is known as Wil Ksi Bax̱hl 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.
Geography
Location and climate Tseax Cone is about 60 kilometres (37 miles) north of Terrace near the Nisga'a villages of Gitwinksihlkw and Gitlaxt'aamiks in Cassiar Land District of northwestern British Columbia, Canada. It lies within a steep-sided, 5 km (3.1 mi) long, east–west valley penetrating the Nass Ranges of the Hazelton Mountains. Tseax Cone is situated at the outlet of Melita Lake, an expansion of Crater Creek which flows west into the Tseax River. Crater Creek gets its name from being in association with Tseax Cone which is located on the eastern side of the creek. The Nass Mountains Ecosection is the main ecosection at the cone. The area has a climate that is somewhat transitional between those of coastal and continental regimes. It is wetter than other areas in the Nass Ranges Ecoregion due to air entering from the Pacific Coast. Much of this Pacific air enters via the Skeena River valley or flows over the Kitimat Ranges, resulting in cloud cover and heavy rain. Short periods of extreme cold temperatures and deep snow occasionally occur as a result of cold Arctic air invading from the north.
Plants and animals
Lichens and mosses cover large portions of lava flows originating from Tseax Cone. They range in colour from green to yellow, reach thicknesses of a few centimetres and give the illusion that the lava flows are covered in fur. Also present on the lava flows in very small quantities are grasses and smaller shrubs. In the Tseax River valley, the lava flows have been almost completely covered by dense rainforest; coastal western hemlock and subalpine mountain hemlock form rainforests in the area. Wildlife in the area includes marmots, goats, bears and moose. Despite being covered by lichens, mosses and rainforests, the lava flows are easily recognizable from aerial and satellite imagery, as well as field observations. 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. The growth of these forests is bolstered by the deposition of silt on the lava flows by local streams, providing soil for vegetation.
Geology and geomorphology
Background Tseax Cone is one of the southernmost volcanoes in the Northern Cordilleran Volcanic Province. 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. The dominant rocks compossing these volcanoes are alkali basalts and hawaiites, but nephelinites, basanites and peralkaline phonolites, trachytes and comendites are locally abundant. These rocks were deposited by volcanic eruptions from 20 million years ago to as recently as a few hundred years ago. Volcanism in the Northern Cordilleran Volcanic Province is thought to be due to rifting of the North American Cordillera, driven by changes in relative plate motion between the North American and Pacific plates.
Petrology
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