Wow Oh Wow! thank you Jeff tepper, your talk was so great and clear I love that your speaking voice was slow enough for this 81 year old to keep up. I really loved the visuals and the explanations that went with them. it was fabulous. I was glued to the screen. what a great teacher you are. Thank you Nick Zentnor for bring stellar folks to us. we are interested. I appreciate this more than you will ever know. Thanks again. looking forward to A to Z Cascades.
What a great episode! Dr. Tepper’s lecture was OUTSTANDING! Tepper’s theory makes a huge amount of sense-he really did an incredible job tying these critical processes together. What a super smart guy! Dr. Tepper’s calm demeanor coupled with his deep expertise marks him as a fabulous instructor. Thank you Dr Tepper and Nick!
Jeff has a way of turning the complex into meaningful pictures. I’ve watched his Granite Falls video several times. He brought together many of the things I’ve learned since watching you in your back yard during COVID. I’ve never been disappointed with any of your guests. Progressing us toward the exciting sessions of your next series beginning in Nov. Then there was the geology-loving, well-spoken young man (with the amazing hair) sharing his history and geology at the end. Honestly, when he showed his appreciation of you, Nick, tears came to my eyes. Thank you, Nick.
This presentation is more than A+. I have been watching Nick since before Covid. This presentation made so much of that which has been presented over the years really understandable. I am not a good multi-piece or multi dimensional thinker-but this presentation overcame all that and I feel like I really really get the picture. Thank you so much.
Kudos to “Kevin” for making a donation to the program. The instinct to altruistically“pay it forward” to some undefined generalized public benefit is the social force that builds civilization. Thanks to Dr. Jeff Tepper for presenting this comprehensive explanation for the many moving parts of this subject. We see in the basaltic lava lakes in the Halemau’mau’ crater of Kilauea periods where the cooler crust forming at the surface of the lake “founders” in the hot fresh lava, presumably because it is cooler and more dense. Can this phenomenon be extended on a mega scale to a “foundering” of 110 Ma old plate material?
Jeff has added a novel (at least to me) hypothesis regarding the Farallon "jump" following the accretion of Siletzia. It's great to have another idea thrown into the conversation. Thank you to Jeff, Nick, and Hannah for putting this highly informative and thought inducing episode together.
Nick, you are a geo star. We all appreciate you bringing these amazing people into our lives, sharing their knowledge and enthusiasm, broadening our understanding of the materials and forces which have formed and continue to form the planet on which we reside.
It's so amazing to see these concepts illustrated in slightly different ways and from the different perspectives of these individual workers; the reiterations and overlaps really consolidate the processes in my layperson's brain. Thanks Nick and Jeff for these awesome insights. We both loved this talk.
An ideal prelude to give everyone a brief background to the upcoming Cascade Volcano series. Great info delivered without fault. Dr Tepper, we all salute you.
Thanks Jeff and Nick. Very interesting and I’m getting psyched for “Cascades A to Z”. As a retired geologist I’m very encouraged by the young people in the audience. They are asking some great questions. We need thoughtful new scientists in our future.
I think what I'm hearing from Jeff are a lot of qualitative arguments based on temperature , density, geologic dating and common sense, however I think that fluid dynamic simulations using phase diagram of the different rock types and how they behave with respect to temperature, pressure and time might help us understand the complicated physics of plate seduction a little better. Things like slab failure, athenosphere up-welling, and other phenomena need computer simulations rather than qualitative arguments.
I absolutely love you reminding people that fooling with their phone while a guest speaker is presenting is RUDE. And it's not that the people are necessarily rude by nature, but some just aren't properly potty trained. We can't be shy about educating on that common decency.
Also, the audience member in this community is actually a participant, so attention directed elsewhere is a person not fulfilling his/her responsibility as a learning community member. I wish students got that-it would revolutionize learning.
I was going to ask if the roll back had anything to do with Silletsia and Jeff answered it before I even asked. Thank you Jeff, your always a treat to listen and learn from
Excellent talk. Jeff Tepper is clear and concise. Many of Nick's talks and interviews are very challenging. This talk sparked for me and my interest for more on the Cascade series. Hey, it's great learning new a new topic. Thank you.
I really enjoyed this presentation by Jeff Teper - he is an inspirational teacher! It sounds as if he is going to be a resource for this winter's AtoZ, and I am looking forward to hearing more from him. Can't believe we are just a few days away from "kick off"!!! Thanks Nick and Jeff for sharing your time and knowledge.
One of the most informative talks yet. Finally some understanding of the resurrection plate. Question... Northern movement of the subduction, connection to Baja/bc?
From the recent interview between Nick and Karin Sigloch yeah the Resurrection plate likely was the last gasp of the Orcas plate which would have been the plate Baja BC took place on. That said while their plate reconstruction models largely align well their models do have a few differences which will have to be rectified, namely Karin's trench position reconstructions based on subducted slabs in the mantle as seen by Seismic tomography have the North Farallon subduction complex offshore with that tomography being backed with its associated accreted terrane units for evidence, offshore and docking onto the continent to become the Cascadia arc. Both models have what looks to be solid evidence backing them but they do have discrepancies IDK how those will be resolved but they agree on the resurrection plate and its eventual subduction beneath Alaska.
Interesting a few late questions that come to mind from this and Nick's guest lectures. 1) What about the clockwise rotation? 2) Sigloch's trench reconstructions have an oceanic trench outboard of NA based on plate motion models which hypothesizes a purely vertical sinking rate, could the arc in question have not been oceanic still? I know her reconstructions have the Orcas plate which is synonymous with the Resurrection plate near the end of its lifetime is that at play here too? From the literature on the Yellowstone Hot Spot Siletzia volcanics there is a record of volcanic activity in eastern Siletzia which gets as young as ~30ish million years before the magmatic hiatus. Also the Camp interview/presentation a few months back was quite elucidating for how the slab failed not so much by completely burning through but by uplifting a section of slab that was partially melting to produce adakites until slab break off was induced both to the west and east detaching a section and opening a window with the remaining rolling back to both the west and the east starting 17 Ma. The reason for the magmatism deflection Camp gave was if memory serves topographic elevations from the uplifted slab bulge supported by independent datasets on the basis of erosion and depositional features in what is now Oregon along of course with the role of corresponding zones of weakness in the slab, and overlying crust if I recall correctly.
Im not getting notified Nick sure would like to join in on the live stream. Fan since the back yard blanket days . Thanks for all you do brother Isaac,Stevens CO. WA
1) Wondering if the slab tear and slab curtain aspects jive with K Sigloch’s interpretation of what she sees in the upper mantle. Does everyone agree that the big ol’ slab curtain under Idaho is Farallon? 2) If the YHS is offshore N Washington creating Siletzia at 55MYA and it’s causing Columbia basalts and calderas in S Idaho 17-0 MYA, where was it in between times? Does this mean that Siletzia was created offshore the Columbia Embayment? UPDATE: Found the answer to 2) in Camp’s paper on Long-Lived YHS
Super interesting talk by Jeff Tepper! And to me yet another teaser for the upcoming alphabet series. Yet another question : as there's a rollback of the remaining Farralon plate after the accretion of Siletzia, shouldn't there be a series of magmas starting in the east and moving to the west just before the Cascades kick off? Kind of like the Challis magmas but a bit more to the south? Or is it the same rollback? I am a bit confused.
On the initial map displayed, there's a "gap" in the Cascade Volcanic Arc at Northern California and Oregon border, is that part of the hotspot's wake?
Why is 110km depth the point that the leading edge turns on? Is it consistently true world wide? Is it were pressure and temp reach sufficient degrees that cause the melting? Could other factors be mineral content, or water content? If water plays a role, is it the water in porosity , or water formed from chemical compounds breaking down due to pressure/temp?
The ~100 km depth for the generation of volcanic-arc magma is a good rule of thumb. The amount of fluid in the form of oceanwater and hydrous minerals (usually sediments) within the descending crust is especially important to the production of subduction-generated magma. As the slab is subjected to increasing pressure and temperature with increasing depth, the fluids are released into the overlying mantle. This dramatically lowers the melting point of the mantle, causing some of it to melt and form magma, which can then make its way to the Earth's surface.
This was a very interesting presentation. I'm watching it later, and I'm at right about the 1h4min mark where there is a question about plate rollback and volcanic activity associated with the 100-110km depth of the plate. Then, at 1h10min there is a further question about this, and a possible answer of a break-off under Colorado. But, if the slab did break off under Colorado, wouldn't there have been volcanism associated with that? Also, wouldn't the break-off cause a temporary rebound of the subducting plate until there is enough extension to cause a roll again? (Which is where I'm guessing the Cascadia Arc activates??)🤔
I was surprised to hear Colorado mentioned, and I wonder if Dr. Tepper misspoke. Colorado seems to be outside the scope of what was going on in the northwest. To be fair, I'm not sure what exact distances are involved if we undo Basin and Range extension, but it is still pretty far away. Slab rollback in Colorado would have originated with the Challis volcanics up in Montana/Idaho that propagated to the south and west. My understanding is that volcanism in Colorado represents the eastern edge of the slab tear and is too young to be part of this story. Also, there has to be a path to allow a slab to sink. If a slab remains an intact sheet there is no way for it to "fall" except along its edge. Multiple tears would hasten the process, and if a slab was ready to break apart and sink it might tear into several pieces.
After watching the presentation, I'm confused how a shallower and faster subduction will create less vulcanism than a slower deeper subduction. Isn't subduction caused vulcanism caused by the friction of the scraping of the moving masses? I would think the faster subduction would cause MORE friction, and so more vulcanism.
The process for creating the majority of volcanism in the Cascade arc is the dewatering of hydrated minerals in the descending crust which releases fluids into the hot overlying mantle. In a process called flux melting, the introduction of water and other fluids lowers the melting temperature of the mantle rocks, resulting in the production of magma, which can then make its way to the Earth's surface to form volcanoes. This typically occurs where the slab reaches a depth of about 100 km (60 mi). The angle at which a slab descends beneath on overriding plate determines how far from the trench volcanism occurs, and whether Cascade arc-type volcanism can even occur. Researchers are investigating relationships between slab dip angles and subduction parameters such as absolute convergence rates, with some suggesting that a faster trenchward motion of the overriding plate promotes lower slab dip while a slower motion induces steeper slabs. But regardless of the convergence rate and its cause, a shallower slab angle increases the lateral distance between the trench and the volcanic arc, and if the angle becomes exceedingly shallow, no volcanoes originating from flux melting are produced. The lack of volcanoes directly above the subducting Yakutat oceanic plateau in southeast Alaska, for example, is attributed to "flat slab" subduction. The Yakutat microplate is converging with the North American plate at a rate of up to 55mm/yr, making it one of the highest convergence rates in the world within the continental crust, about 2 to 3 times greater than the current convergence rate for the Himalaya. Hope this helps.
Watched it, loved it, want more... but when are you going to give midwestern kids a break? Try making geology interesting for flyover kids that dont see mountains out of their bedroom windows. I grew up in western chicago with only buildings to look at and no support when my attention turned to a small geology book - ROCKS AND MINERALS by Zim. Now we have internet channels but ive seen no one bring geology to youngsters in the flatlands. No one supported my interests in earth science so i went a different way - radio electronics. However, i like to think i might have made a great field geologist. If i was young again, and knew what i know now, i might have been in attendance at this lecture with plenty of questions. No doubt western geology is exciting and fun... how about showing flatland kids the marvels of their environments as well. Respectfully, clyde
![NLE Choppa - Or What ft. 41 (Orchestra Mix) [Official Music Video]](http://i.ytimg.com/vi/biOFASEgSOM/mqdefault.jpg)
Wow Oh Wow! thank you Jeff tepper, your talk was so great and clear I love that your speaking voice was slow enough for this 81 year old to keep up. I really loved the visuals and the explanations that went with them. it was fabulous. I was glued to the screen. what a great teacher you are. Thank you Nick Zentnor for bring stellar folks to us. we are interested. I appreciate this more than you will ever know. Thanks again. looking forward to A to Z Cascades.
What a great episode! Dr. Tepper’s lecture was OUTSTANDING! Tepper’s theory makes a huge amount of sense-he really did an incredible job tying these critical processes together. What a super smart guy! Dr. Tepper’s calm demeanor coupled with his deep expertise marks him as a fabulous instructor. Thank you Dr Tepper and Nick!
Jeff has a way of turning the complex into meaningful pictures. I’ve watched his Granite Falls video several times. He brought together many of the things I’ve learned since watching you in your back yard during COVID. I’ve never been disappointed with any of your guests. Progressing us toward the exciting sessions of your next series beginning in Nov. Then there was the geology-loving, well-spoken young man (with the amazing hair) sharing his history and geology at the end. Honestly, when he showed his appreciation of you, Nick, tears came to my eyes. Thank you, Nick.
This presentation is more than A+. I have been watching Nick since before Covid.
This presentation made so much of that which has been presented over the years really understandable. I am not a good multi-piece or multi dimensional thinker-but this presentation overcame all that and I feel like I really really get the picture. Thank you so much.
Kudos to “Kevin” for making a donation to the program. The instinct to altruistically“pay it forward” to some undefined generalized public benefit is the social force that builds civilization. Thanks to Dr. Jeff Tepper for presenting this comprehensive explanation for the many moving parts of this subject.
We see in the basaltic lava lakes in the Halemau’mau’ crater of Kilauea periods where the cooler crust forming at the surface of the lake “founders” in the hot fresh lava, presumably because it is cooler and more dense. Can this phenomenon be extended on a mega scale to a “foundering” of 110 Ma old plate material?
Jeff has added a novel (at least to me) hypothesis regarding the Farallon "jump" following the accretion of Siletzia. It's great to have another idea thrown into the conversation. Thank you to Jeff, Nick, and Hannah for putting this highly informative and thought inducing episode together.
Nick, you are a geo star. We all appreciate you bringing these amazing people into our lives, sharing their knowledge and enthusiasm, broadening our understanding of the materials and forces which have formed and continue to form the planet on which we reside.
Jeff Tepper is an awesome teacher!💛✨😃Nick, thank you for reminding us to watch this!!
It's so amazing to see these concepts illustrated in slightly different ways and from the different perspectives of these individual workers; the reiterations and overlaps really consolidate the processes in my layperson's brain. Thanks Nick and Jeff for these awesome insights. We both loved this talk.
Thank you Nick for presenting Dr. Tepper again. We always learn so much from what he and his students have discovered.
An enjoyable and informative talk. I never really thought about how subduiction actually started !
maybe the best lecture I've ever seen on this channel. Keep up the good work!
An ideal prelude to give everyone a brief background to the upcoming Cascade Volcano series. Great info delivered without fault. Dr Tepper, we all salute you.
Well, with a transform fault
@@rmsrmsrmsrms and a megathrust fault.
wonderful presentation by Jeff Tepper, clearly explaining the Cascade arc's formation and relevance at a global scale.
Wow, what great graphics! Jeff explains so clearly too. Very grateful and intrigued.
I like Jeff so much. I could listen to him all day. Thank you for bringing him to us Nick!
Thanks Jeff and Nick. Very interesting and I’m getting psyched for “Cascades A to Z”. As a retired geologist I’m very encouraged by the young people in the audience. They are asking some great questions. We need thoughtful new scientists in our future.
Fantastic talk. Really appreciate these lectures and I learn a lot every time!
I think what I'm hearing from Jeff are a lot of qualitative arguments based on temperature , density, geologic dating and common sense, however I think that fluid dynamic simulations using phase diagram of the different rock types and how they behave with respect to temperature, pressure and time might help us understand the complicated physics of plate seduction a little better. Things like slab failure, athenosphere up-welling, and other phenomena need computer simulations rather than qualitative arguments.
I lived Seattle for 15 years and now Guam for 15 years. Life on 2 subduction zones. Love the deep dives since covid March 2020
I absolutely love you reminding people that fooling with their phone while a guest speaker is presenting is RUDE. And it's not that the people are necessarily rude by nature, but some just aren't properly potty trained. We can't be shy about educating on that common decency.
Also, the audience member in this community is actually a participant, so attention directed elsewhere is a person not fulfilling his/her responsibility as a learning community member. I wish students got that-it would revolutionize learning.
Would depend? Student's utilize phone to learn. Speaker's lecture triggered questions or answers to clarify research.
I was going to ask if the roll back had anything to do with Silletsia and Jeff answered it before I even asked. Thank you Jeff, your always a treat to listen and learn from
Excellent talk. Jeff Tepper is clear and concise. Many of Nick's talks and interviews are very challenging. This talk sparked for me and my interest for more on the Cascade series. Hey, it's great learning new a new topic. Thank you.
Great lecture, thank you! 😊
Good morning from Edmonds Wa. Excellent episode!
I really enjoyed this presentation by Jeff Teper - he is an inspirational teacher! It sounds as if he is going to be a resource for this winter's AtoZ, and I am looking forward to hearing more from him. Can't believe we are just a few days away from "kick off"!!! Thanks Nick and Jeff for sharing your time and knowledge.
I learned a lot. Thank you.
One of the most informative talks yet. Finally some understanding of the resurrection plate. Question... Northern movement of the subduction, connection to Baja/bc?
From the recent interview between Nick and Karin Sigloch yeah the Resurrection plate likely was the last gasp of the Orcas plate which would have been the plate Baja BC took place on. That said while their plate reconstruction models largely align well their models do have a few differences which will have to be rectified, namely Karin's trench position reconstructions based on subducted slabs in the mantle as seen by Seismic tomography have the North Farallon subduction complex offshore with that tomography being backed with its associated accreted terrane units for evidence, offshore and docking onto the continent to become the Cascadia arc.
Both models have what looks to be solid evidence backing them but they do have discrepancies IDK how those will be resolved but they agree on the resurrection plate and its eventual subduction beneath Alaska.
Oh, to be young again, studying Geology at CWU...
Thx, Jeff & Nick. Interesting stuff as usual.
The roll back for both plate sections makes sense! What about the klamaths in cali? Any relation to this?
Interesting a few late questions that come to mind from this and Nick's guest lectures.
1) What about the clockwise rotation?
2) Sigloch's trench reconstructions have an oceanic trench outboard of NA based on plate motion models which hypothesizes a purely vertical sinking rate, could the arc in question have not been oceanic still? I know her reconstructions have the Orcas plate which is synonymous with the Resurrection plate near the end of its lifetime is that at play here too?
From the literature on the Yellowstone Hot Spot Siletzia volcanics there is a record of volcanic activity in eastern Siletzia which gets as young as ~30ish million years before the magmatic hiatus. Also the Camp interview/presentation a few months back was quite elucidating for how the slab failed not so much by completely burning through but by uplifting a section of slab that was partially melting to produce adakites until slab break off was induced both to the west and east detaching a section and opening a window with the remaining rolling back to both the west and the east starting 17 Ma. The reason for the magmatism deflection Camp gave was if memory serves topographic elevations from the uplifted slab bulge supported by independent datasets on the basis of erosion and depositional features in what is now Oregon along of course with the role of corresponding zones of weakness in the slab, and overlying crust if I recall correctly.
Im not getting notified Nick sure would like to join in on the live stream.
Fan since the back yard blanket days . Thanks for all you do brother
Isaac,Stevens CO. WA
Watching from Seattle ❤
1) Wondering if the slab tear and slab curtain aspects jive with K Sigloch’s interpretation of what she sees in the upper mantle. Does everyone agree that the big ol’ slab curtain under Idaho is Farallon? 2) If the YHS is offshore N Washington creating Siletzia at 55MYA and it’s causing Columbia basalts and calderas in S Idaho 17-0 MYA, where was it in between times? Does this mean that Siletzia was created offshore the Columbia Embayment? UPDATE: Found the answer to 2) in Camp’s paper on Long-Lived YHS
Super interesting talk by Jeff Tepper! And to me yet another teaser for the upcoming alphabet series.
Yet another question : as there's a rollback of the remaining Farralon plate after the accretion of Siletzia, shouldn't there be a series of magmas starting in the east and moving to the west just before the Cascades kick off? Kind of like the Challis magmas but a bit more to the south? Or is it the same rollback? I am a bit confused.
On the initial map displayed, there's a "gap" in the Cascade Volcanic Arc at Northern California and Oregon border, is that part of the hotspot's wake?
Good to see some snow in the crowd....Thanks for sharing!!!!
Great talk, I love it❤ i never thought in the velocity of the subdcion slabs😲
Why is 110km depth the point that the leading edge turns on? Is it consistently true world wide? Is it were pressure and temp reach sufficient degrees that cause the melting? Could other factors be mineral content, or water content? If water plays a role, is it the water in porosity , or water formed from chemical compounds breaking down due to pressure/temp?
The ~100 km depth for the generation of volcanic-arc magma is a good rule of thumb. The amount of fluid in the form of oceanwater and hydrous minerals (usually sediments) within the descending crust is especially important to the production of subduction-generated magma. As the slab is subjected to increasing pressure and temperature with increasing depth, the fluids are released into the overlying mantle. This dramatically lowers the melting point of the mantle, causing some of it to melt and form magma, which can then make its way to the Earth's surface.
I miss seeing the Zentnerd comments on replay. A lot of good commentary, and since I can't be here for the live, I miss out.
Does the slab tear have any relation to the Yellowstone hot spot movement?
This was a very interesting presentation. I'm watching it later, and I'm at right about the 1h4min mark where there is a question about plate rollback and volcanic activity associated with the 100-110km depth of the plate. Then, at 1h10min there is a further question about this, and a possible answer of a break-off under Colorado. But, if the slab did break off under Colorado, wouldn't there have been volcanism associated with that? Also, wouldn't the break-off cause a temporary rebound of the subducting plate until there is enough extension to cause a roll again? (Which is where I'm guessing the Cascadia Arc activates??)🤔
I was surprised to hear Colorado mentioned, and I wonder if Dr. Tepper misspoke. Colorado seems to be outside the scope of what was going on in the northwest. To be fair, I'm not sure what exact distances are involved if we undo Basin and Range extension, but it is still pretty far away. Slab rollback in Colorado would have originated with the Challis volcanics up in Montana/Idaho that propagated to the south and west. My understanding is that volcanism in Colorado represents the eastern edge of the slab tear and is too young to be part of this story.
Also, there has to be a path to allow a slab to sink. If a slab remains an intact sheet there is no way for it to "fall" except along its edge. Multiple tears would hasten the process, and if a slab was ready to break apart and sink it might tear into several pieces.
Sac, CA
After watching the presentation, I'm confused how a shallower and faster subduction will create less vulcanism than a slower deeper subduction. Isn't subduction caused vulcanism caused by the friction of the scraping of the moving masses? I would think the faster subduction would cause MORE friction, and so more vulcanism.
The process for creating the majority of volcanism in the Cascade arc is the dewatering of hydrated minerals in the descending crust which releases fluids into the hot overlying mantle. In a process called flux melting, the introduction of water and other fluids lowers the melting temperature of the mantle rocks, resulting in the production of magma, which can then make its way to the Earth's surface to form volcanoes. This typically occurs where the slab reaches a depth of about 100 km (60 mi).
The angle at which a slab descends beneath on overriding plate determines how far from the trench volcanism occurs, and whether Cascade arc-type volcanism can even occur. Researchers are investigating relationships between slab dip angles and subduction parameters such as absolute convergence rates, with some suggesting that a faster trenchward motion of the overriding plate promotes lower slab dip while a slower motion induces steeper slabs. But regardless of the convergence rate and its cause, a shallower slab angle increases the lateral distance between the trench and the volcanic arc, and if the angle becomes exceedingly shallow, no volcanoes originating from flux melting are produced.
The lack of volcanoes directly above the subducting Yakutat oceanic plateau in southeast Alaska, for example, is attributed to "flat slab" subduction. The Yakutat microplate is converging with the North American plate at a rate of up to 55mm/yr, making it one of the highest convergence rates in the world within the continental crust, about 2 to 3 times greater than the current convergence rate for the Himalaya.
Hope this helps.
5 x5
Watched it, loved it, want more... but when are you going to give midwestern kids a break? Try making geology interesting for flyover kids that dont see mountains out of their bedroom windows. I grew up in western chicago with only buildings to look at and no support when my attention turned to a small geology book - ROCKS AND MINERALS by Zim. Now we have internet channels but ive seen no one bring geology to youngsters in the flatlands. No one supported my interests in earth science so i went a different way - radio electronics. However, i like to think i might have made a great field geologist. If i was young again, and knew what i know now, i might have been in attendance at this lecture with plenty of questions. No doubt western geology is exciting and fun... how about showing flatland kids the marvels of their environments as well. Respectfully, clyde