H. Teanaway Bimodal

[@Dennis52947]

👍 Caught the replay, greatly enjoyed.

[@sharonseal9150]

No hurry to get to the modern Cascade arc Nick - this has been a blast! Looking forward to the next one.

[@t48wolf]

Wonderful fulling episode thanks to all who contributed especially Proffessor Zenter

[@pathorgan8643]

Such a GREAT episode bringing many prior and new concepts to satisfying comprehension!!!

[@yukigatlin9358]

Awesome, thanks, Nick, Mike,,,,,YOU MADE my day! Must watch and enjoy the moment video!!😘💞✨💗

[@_Michiel_]

Loved this episode, Nick! (and all the others 😉) I especially liked how you added in the older videos about the blue agates and the wired gold. It gives us a broader insight in the origins thereof. Thank you!

[@DouglasBlack-ob9dy]

Thanks Nick! This was an exciting episode. All is helping me in putting the geologic pieces together. Thankful for the samples and slides and map locations. Very helpful!

[@xwiick]

Thanks for all the hard work on these videos!

[@Vickie-Bligh]

Nick, I, for one, appreciate giving the full background of the Cascade basement. The Arc wasn't a solitary story, and you are giving us the foundation. The Cascades are so full of interesting features. I was born & raised here. I always knew the Cascades were volcanic. What I didn't know until I found you was the exciting rock that exists there. The Cascades are messy and choppy and so worth our time. Thank you for teaching us, for showing us, for demonstrating what an awesome place Washington State is.

[@RonSparks2112]

Another great instructive and challenging video. I want to especially thank you and Dr. Tepper for posting the excellent "Bimodal Vulcanism" note. This provides an answer to a question I've had since visiting Newberry Volcanic Monument this summer as part of a wide ranging visit to the Cascades. Newberry just didn't seem to fit, and the question had begun to bug me as I learned a little more about bimodal vs. BADR vulcanism. This is science, so I know this is AN answer, and not necessarily THE answer to my question, but it seems like a pretty good one, and I'll go with it until shown otherwise. Again, many thanks.

[@pbrassington1]

Aloha from Bali! Thank you for continuing this awesome series on Cascade volcanism.

[@kellyhorton1462]

That was excellent. Ty. Wish you could date one of those samples. Just beautiful. Have a great Christmas weekend.

[@davec9244]

thank you

[@jillrector7176]

Love that you’re still doing down-town lectures…that’s where I found you online a while back.

[@AvanaVana]

1:18:40 Beautiful map of the feeder dikes by Otis. Remember though that the PNW has rotated by 50° since the Eocene. So the Teanaway extension was perpendicular to a perfectly north-south active margin in the Eocene. The phreatomagmatism really interests me. I can’t think of a modern analog for this-a tropical, low-elevation maar-diatreme/fissure complex with bimodal rhyolite caldera volcanism. There are plenty of maar+caldera fields in the Pleistocene of Oregon, there are the Hopi Buttes volcanoes from the Mio-Pliocene in Arizona, the Pleistocene Potrillo Volcanic Field in New Mexico, and the Pinacate volcanic field in Mexico, but those are all mostly too northern latitude-they were wetter and drowned with pluvial lakes and wetlands when they were erupted, but not exactly tropical by any means. Also, these fields are mostly just basaltic monogenetic fields-not bimodal volcanism with rhyolitic calderas. There are tropical maar fields in Indonesia (Lamongan Volcanic Field on Java) and the Philippines (East Luzon), and these are associated with active arcs and even some caldera volcanoes, but they aren’t bimodal as far as I am aware-not slab break off magmatism at this point. The Nevsehir-Acigöl Volcanic Complex in Turkey fits the styles of volcanism, but again-not tropical. Perhaps some volcanic areas of Mexico and Central America are somewhat close-I am thinking of Aljojuca Maar and associated maars and silicic volcanism in the Trans-Mexican Volcanic belt-pretty tropical. But the quantity of basalt erupted is not nearly as much as the Teanaway it seems. The Roman/Central Magmatic Province of Italy features tons of maar-diatreme volcanoes (Colli Albani, etc) and silicic caldera volcanism (Campi Flegrei and the Campanian Ignimbrite suoervolcanic eruption), but again, the basaltic fissure volcanism and lava production is not near the level of the Teanaway-and not tropical. The particular combination of tectonic setting, style of volcanism, and climate/biome that the Teanaway formation represents is very unique. Also regarding what that Carl guy said about “rubies”: I always thought that ruby was only associated with high grade granulated-facies metamorphism, so I looked this up thinking he was mistaken, but I’ve come to learn that there are actually occurrences of rubies associated with continental alkaline basaltic volcanism. This is a relatively new finding-the dogma has always been ruby=high grade metamorphism and ancient, denuded orogenic belts. 1:45:00 Ok, so this changes things. So do we even have actual bimodal volcanism ala Tepper? Or we have both the Eocene bimodal volcanism plus younger cascades rhyolites coming up through the Teanaway? What proportion of the rhyolites are coeval with the basalts versus the younger set?

[@JenniferWaters-n9s]

Merry Christmas!!

[@timbyrne914]

This was a good episode for the day after Christmas: not many new ideas to digest. Next year I need to take a trip through the Teanaway concentrating on the rocks underfoot instead of the much more ostentatious rocks in the vicinity.

[@TheZinmo]

Those old maps are indeed georgeous.

[@KSparks80]

Missed the first 25 minutes live. (Dog ate my homework? lol) Watched the Index Granite vid from "Nick on the Rocks" a bit ago. Good stuff. Thx!

[@Pidxr]

Is the break off why there are little rhyolite bits on all the trails in the Col Rvr Gorge ?

[@bryansavage5056]

So has the broken off section of the plate been fueling the Cascade volcanics and also helping to create the Cascades

[@mr.morelock]

So... are there any spidergraphs of the young Rhyolites? Are they fresh arc, or could they be breakoff stuff pushed ahead of arc magmas?

[@jonathanblubaugh5049]

@nick Statia Gordon is our uplift expert, right? maybe at least as it pertains to metamorphic petrology, geochem, depth of burial, right?

[@guiart4728]

If the dikes are intruding through cracks caused by uplift prior to 49Ma would the same directional trending cracks apply to the younger 26Ma intrusive dikes? This in response to one of the questions in the QA at the end…

[@t.m.p.7242]

I thought the dikes had rotated 45 degrees, -or was that a different set of dikes??

[@steveneiffel8227]

Looking forward getting back to Basil Tikoff take on the whole thing with Idaho, Cascades and everything. Sure he will have his own take on all things said until now.

[@mikerod5396]

What happened to the chat? Am I missing a setting?

[@charlesward8196]

The live chat goes away after the live stream, Nick has no control over that, it is a You Tube thing.

[@mr.morelock]

@@charlesward8196 It does come back, but the timing is all up to KZbin.

[@RichardStephens-lq3ou]

Depends on WHO broke the plate