Talk:Tseax Cone/Archive 1

Latest comment: 5 years ago by Bill-on-the-Hill in topic 1700 Cascadia earthquake
Archive 1

Incomplete Sentence?

In the section Eruptive History the following sentence seems incomplete "It is the only eruption in Canada for which legends of First Nations people have unproven." What is unproven? Also the previous sentence refers to two prior erruptions 220 and 650 years ago. Which of the two does the quoted text refer to?

Anyway, just pointing the issue out. The grand total of my knowledge about the event comes from this article. So I have no idea as to what to add to correctly clarify it. 205.251.229.73 06:30, 6 October 2007 (UTC)

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1700 Cascadia earthquake

Just noticed the recently added information in the 18th century eruption section. How could the Tseax eruption be linked to the 1700 Cascadia earthquake if Tseax lies about 400 kilometers north of the Cascadia subduction zone? I have never herd of this theory. Just because Tseax erupted after 1668 and the 1700 Cascadia earthquake had widespread effects does not mean it was triggered by that earthquake. If the 1700 Cascadia earthquake created or caused an eruption at Tseax Cone the volcano would most likely be subduction-related because the 1700 Cascadia earthquake was a megathrust earthquake that occured at the Cascadia subduction zone. This would make Tseax part of the Cascade Volcanoes. But it isn't. Tseax is part of the Northern Cordilleran Volcanic Province where rift-related volcanism occurs because the rock composition of Tseax Cone is similar to other Northern Cordilleran volcanoes and not similar to volcanoes associated with subduction zones. Black Tusk (talk) 23:58, 16 July 2009 (UTC)

I am also doubtful with the source being used. It says: The basaltic Tseax flow is the product of one of only two eruptions in western Canada during the last thousand years. If I am understanding this sentence correctly, it sounds as if the 18th century eruption is one of only two eruptions in western Canada in the past thousand years. How can this be true if volcanoes such as Lava Fork, Silverthrone or Edziza have also produced lava flows in the past thousand years? If the sentence I quoted is insted talking about Tseax Cone it should say "Tseax Cone", not "Tseax flow". Black Tusk (talk) 00:33, 17 July 2009 (UTC)
For the "how", I quote from the abstract of that paper: "It is proposed that both magmatic components [there were apparently two petrologically different ones that contributed to the flow -- B-o-t-H] were contained within a steep conduit. Gas produced by degassing of magma in the lower part of the conduit ascended, heated magma in the upper part, coarsening plagioclase, and then continued to the surface along fissures. This stable configuration was disrupted by the Cascadia earthquake: dilatation widened the conduit and enabled both magmas to rise to the surface along existing fissures." I have not read the whole paper (retired and can't get it for free any more), so cannot make informed comments on the plausibility of this, nor on the part about "one of only two eruptions." An expert on this subject is a good friend, and I'll ask the next time I see him. As for why "flow" rather than "cone," it's the flow that's interesting to the author of the paper, not the scoria cone that's only a minor manifestation of the surface activity. -- Bill-on-the-Hill (talk) 21:53, 2 July 2018 (UTC)