View source for Earth:Tseax Cone

{{Short description|Cinder cone and adjacent lava flows in British Columbia, Canada}}
{{Infobox mountain
| name = Tseax Cone
| photo = File:Tseax Cone.jpg
| photo_caption = Tseax Cone with Melita Lake in the background
| elevation_m = 610
| elevation_ref = 
| prominence = 
| location = British Columbia, {{wipe|Canada}}
| range = Nass Ranges
| map = British Columbia |relief=1
| map_size = 230
| label_position = right
| coordinates = {{coord|55|06|39|N|128|53|56|W|display=inline,title|type:mountain_region:CA}}
| topo_maker = [[Earth:National Topographic System|NTS]]
| topo_map = {{Canada NTS Map Sheet|103|J|2}}
| type = [[Earth:Cinder cone|Cinder cone]]
| age = [[History:History|Historical]]
| volcanic_arc/belt = [[Earth:Northern Cordilleran Volcanic Province|Northern Cordilleran Volcanic Province]]
| last_eruption = 1690 ± 150 years (18th deadliest eruption of all time)
| first_ascent = 
| easiest_route = drive
}}

The '''Tseax Cone''' ({{IPAc-en|ˈ|s|iː|æ|k|s}} {{respell|SEE|aks}}), also called the '''Tseax River Cone''' or the '''Aiyansh Volcano''', <!-- references needed here on the name --> is a young and active [[Earth:Cinder cone|cinder cone]] and adjacent lava flows associated with the Nass Ranges and the [[Earth:Northern Cordilleran Volcanic Province|Northern Cordilleran Volcanic Province]]. It is located east of Crater Creek at outlet of Melita Lake, southeast of Gitlakdamix and {{convert|60|km|mi|0}} north of Terrace, British Columbia, {{wipe|Canada}}.

The volcano is in a valley above and east of the Tseax River, about {{convert|20|km|mi|0}} south of the river's junction with the larger Nass River. The Tseax Cone is one of the most accessible volcanic centres in British Columbia.<ref name="AS"/>

==Geology==
[[File:Northern Cordilleran Volcanic Province map.jpg|thumb|Map of Northern Cordilleran Volcanic Province showing location of Tseax Cone]]
The Tseax Cone is in the southern part of the [[Earth:Northern Cordilleran Volcanic Province|Northern Cordilleran Volcanic Province]] and is therefore part of the [[Earth:Ring of Fire|Ring of Fire]].  It has been the site of some of the youngest volcanic eruptions in Canada.<ref>{{cite gvp|vn=320100|name=Tseax River Cone|access-date=2008-02-26}}</ref> It has been active at least twice in the past few hundred years and other remnants of lava flows exist in the area. It is {{convert|290|m|ft|0|abbr=on}} in diameter at its base and rests on the remnants of an earlier and somewhat larger, dissected, {{convert|460|m|ft|0|abbr=on}} diameter cone.<ref name="SI"/> The volcano is made of [[Earth:Volcanic bomb|volcanic bomb]]s and [[Earth:Scoria|cinder]]s with a [[Earth:Volcanic crater|crater]] at its summit where a churning [[Earth:Lava lake|lava lake]] poured and overflowed its rim during the 18th century.<ref name="AS">[http://www.env.gov.bc.ca/bcparks/explore/parkpgs/nisgaa.html Nisga'a Memorial Lava Beds Provincial Park] Retrieved on 2008-02-13</ref>

Volcanism at the Tseax Cone is caused by the [[Earth:Rift|rift]]ing of the Earth's [[Earth:Crust (geology)|crust]] where two parts of the [[Earth:North American Plate|North American Plate]] are breaking apart. The rifting is the result of the [[Earth:Pacific Plate|Pacific Plate]] sliding northward along the [[Earth:Transform fault|transform]] Queen Charlotte Fault, on its way to the [[Earth:Aleutian Trench|Aleutian Trench]].<ref>[http://gsc.nrcan.gc.ca/volcanoes/cat/belt_stikine_e.php Catalogue of Canadian volcanoes – Stikine volcanic belt] Retrieved on 2008-02-13 {{webarchive |url=https://web.archive.org/web/20090608031644/http://gsc.nrcan.gc.ca/volcanoes/cat/belt_stikine_e.php |date=June 8, 2009 }}</ref>

The [[Earth:Lava|lava]] emitted in eruptions at the Tseax Cone is fluid. Its lavas are made of [[Earth:Basalt|basalt]], a common grey to black or dark brown extrusive [[Earth:Volcanic rock|volcanic rock]] low in [[Chemistry:Silica|silica]] content (the lava is [[Earth:Mafic|mafic]]) that is usually fine-grained due to rapid cooling of lava on the Earth's surface. Pāhoehoe is found at the volcano, which has a smooth, billowy, undulating, or ropy surface. A pāhoehoe flow typically advances as a series of small lodes and toes that continually break out from a cooled crust.<ref name="AQ">[http://www.geology.sdsu.edu/how_volcanoes_work/Basaltic_lava.html Basaltic Lava] {{Webarchive|url=https://web.archive.org/web/20181008083242/http://www.geology.sdsu.edu/how_volcanoes_work/Basaltic_lava.html |date=2018-10-08 }} Retrieved on 2008-02-13</ref> It also forms [[Earth:Lava tube|lava tube]]s where the minimal heat loss maintains low viscosity.  However, there is also basaltic lava at the volcano characterized by a rough or rubbly surface composed of [[Earth:Lava#.CA.BBA.CA.BB.C4.81|clinker]] called ʻaʻā. The clinkery surface covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface.<ref name="AQ"/>

==17th-century eruption==
[[Image:Nass Valley Lava Beds.jpg|thumb|right|250px|Nisga'a Memorial Lava Beds Provincial Park]]
[[Image:Tseax Lava Rock.jpg|thumb|right|250px|A volcanic rock erupted from the Tseax Cone.]]
The Tseax Cone was the source for a major lava flow eruption between 1668 and 1714 that travelled into the Tseax River, dammed it, and formed Lava Lake. The flow subsequently travelled {{convert|11|km|mi|0|abbr=on}} north to the Nass River, where it filled the flat valley floor for an additional {{convert|10|km|mi|0|abbr=on}}, making the entire lava flow approximately {{convert|22.5|km|mi|0|abbr=on}} long.<ref name="SI"/>

The Nass River valley contains abundant tree casts and [[Earth:Lava tube|lava tube]]s. The tree casts were formed when the hot lava flow burned out tree trunks and left holes in the lava.<ref name="AS"/> Lava tubes formed when the low-viscosity hot alkali [[Earth:Basalt|basalt]]ic lava travelled beneath the surface, which eventually flowed out and left the crust as the roof and walls of the tubes.<ref name="AS"/>

Legends of the Nisga'a people tell of a prolonged period of disruption by the volcano, including the destruction of two Nisga'a villages.<ref>[http://atlas.nrcan.gc.ca/site/english/maps/environment/naturalhazards/volcanoes/1 The Atlas of Canada – Volcanoes] Retrieved on 2008-02-13 {{webarchive |url=https://web.archive.org/web/20090217001048/http://atlas.nrcan.gc.ca/site/english/maps/environment/naturalhazards/volcanoes/1 |date=February 17, 2009}}</ref> Several Nisga'a people dug pits for shelter but approximately 2,000 Nisga'a people died from volcanic gases and poisonous smoke (most likely from asphyxiation by [[Chemistry:Carbon dioxide|carbon dioxide]]).<ref name="SI"/> The Nisga'a story of the destruction is Canada's worst known geological disaster.<ref>[http://www.bcminerals.ca/pdf/CanadianVolcanoes-CH2005.pdf Volcanoes of Canada] Retrieved on 2008-04-20 {{webarchive |url=https://web.archive.org/web/20070810085815/http://www.bcminerals.ca/pdf/CanadianVolcanoes-CH2005.pdf |date=August 10, 2007 }}</ref>

The lava beds, which reach {{convert|12|m|ft|0|abbr=on}} above the road in some places, are the burial ground of these people. It is the only eruption in Canada for which legends of First Nations people have been verified.<ref name="SI">[http://gsc.nrcan.gc.ca/volcanoes/cat/volcano_e.php?id=svb_tsx_107 Geological Survey of Canada: Tseax Cone] Retrieved on 2008-02-13 {{webarchive |url=https://web.archive.org/web/20080111031918/http://gsc.nrcan.gc.ca/volcanoes/cat/volcano_e.php?id=svb_tsx_107 |date=January 11, 2008 }}</ref> The lava flow can also be found near modern Nisga'a villages, such as Gitlakdamix. This eruption is just one of hundreds that have modified the landscape of western Canada over the past million years.

It has recently been suggested that the Tseax eruption was related to the Cascadia earthquake of 26 January 1700,<ref>Higgins, M.D., 2009, The Cascadia megathrust earthquake of 1700 may have rejuvenated an isolated basalt volcano in western Canada: Age and petrographic evidence. [https://dx.doi.org/10.1016/j.jvolgeores.2008.10.016 Journal of Volcanology and Geothermal Research, 179: 149–156.]</ref> which was the most powerful earthquake during the last 1000 years in the Pacific Northwest. 

Before the 17th century eruption, the Tseax Cone had erupted in 1325.<ref>[http://volcano.und.edu/vwdocs/Gases/dead.html Deadly Gases] Retrieved on 2008-02-13  {{webarchive |url=https://web.archive.org/web/20080324110546/http://volcano.und.edu/vwdocs/Gases/dead.html |date=March 24, 2008 }}</ref>

==Potential for a future eruption==
Today, the [[Earth:Volcano|volcano]] lies dormant within Nisga'a Memorial Lava Beds Provincial Park. Gases currently being emitted by the volcano are evidence that the volcano is still active and potentially dangerous. Signs of unrest such as seismic activity and increased gas output will almost certainly precede any future eruptive activity from the Tseax Cone.

If the Tseax Cone were to erupt, its effects would be felt throughout the interior of British Columbia. There may be a repeat of the poisonous gas disaster that happened to the Nisga'a people during the last eruption.<ref name="SI"/> If the lava flows are voluminous enough, they could spark [[Biology:Wildfire|forest fires]] and dam local rivers, crippling the local ecosystem. This would have disastrous short-term consequences for the important salmon fisheries found along the Nass River system.

Further study and monitoring of the volcano is necessary in order to predict when the Tseax Cone might erupt, perhaps giving those living downslope and downwind the opportunity to evacuate, much like that which preceded the [[Earth:1980 eruption of Mount St. Helens|1980 eruption of Mount St. Helens]].<ref name="SI"/>

==See also==
* List of disasters in Canada
* List of disasters in Canada by death toll
* [[Earth:List of Northern Cordilleran volcanoes|List of Northern Cordilleran volcanoes]]
* List of volcanic eruptions by death toll
* List of volcanoes in Canada
* [[Earth:Northern Cordilleran Volcanic Province|Northern Cordilleran Volcanic Province]]
* Volcanology of Canada
* Volcanology of Western Canada

==References==
{{reflist}}

==External links==
* [http://volcano.und.edu/vwdocs/volc_images/north_america/canada/Final-Tseax.html Volcano World] {{Webarchive|url=https://web.archive.org/web/20080511220946/http://volcano.und.edu/vwdocs/volc_images/north_america/canada/Final-Tseax.html |date=2008-05-11 }}
* "Ignis: a Parable of the Great Lava Plain in the Valley of Eternal Bloom, Naas River, British Columbia (1918)<ref name="McCullagh 1918">{{cite web |last1=McCullagh |first1=J. B. |title=Ignis : a parable of the Great Lava Plain in the valley of "Eternal Bloom", Naas River, British Columbia |url=http://eco.canadiana.ca/view/oocihm.15537/2?r=0&s=1 |website=Early Canadiana Online |publisher=Aiyansh, BC |access-date=July 20, 2019}}</ref>[http://eco.canadiana.ca/view/oocihm.15537/2?r=0&s=1]
* [http://ilmbwww.gov.bc.ca/bcgn-bin/bcg10?name=40915 BCGNIS Geographic Name Details: Tseax Cone] {{Webarchive|url=https://archive.is/20070815193807/http://ilmbwww.gov.bc.ca/bcgn-bin/bcg10?name=40915 |date=2007-08-15 }}


[[Category:Active volcanoes]]

{{Sourceattribution|Tseax Cone|1}}