Ah the Mid continent rift system it was a fascinating feature to learn about, if it wasn't the Grenville which shut it off what did a plume moving too far away? And given how geology tends to reuse geological weak points during future tectonic deformation events what do you think the odds of this structure getting reactivated at some point in the geologic future given how prominent it is as a feature? One thing fascinating line of evidence for Rodina reconstruction is the linking of sediment grains from sedimentary units of that time to ancient cratonic source rocks to effectively trace out a former river system that crossed from North America into what is now Australia. I'm not sure if there are other examples where that technique has been used since it requires ancient river deposits of the appropriate age and very distinct zircon source rocks but there is something about tracing a former river system across two continents now on the opposite sides of the planet. And on the note of zircons it is insane how durable they are with young volcanic rocks from hot spots like Hawaii the Galápagos Reunion Rapa Nui etc. sometimes bringing back up preserved zircons from ancient subducted crust some of which have ages indicating they go back to the Paleozoic if not older. Laboratory simulations and modeling have subsequently revealed that yeah zircons can survive in the upper mantle and then under the right circumstances get brought back to the surface as their source rocks become melted or entrained in magma as Xenoliths. It was apparently discovered by accident in some lava samples from Kilauea which lead scientists to check elsewhere and sure enough there are little bits of these ancient zircons mixed into other young hot spot volcanic rocks without said zircons getting reset.
Some people think part of the rift was successful. I don't think it was. The Grenville is still a viable hypothesis. Personally, I think plume activity elsewhere and preferred rifting on other continents could not maintain the magma chamber(s). So when they ran out, that was it. Great point about reactivation. The MCR actually was a reactivation...sort of. In the Lake Superior-Huron area, the continent did successfully rift 2.5 Ga. By the time the MCR started, there were some new accretions to North America, one being in the general vacinity. It was already weak. Could it rift here again? It very well could.
It was fun for me to return in memory to Little Presque Isle, which I visited with my son and parents in about 1990. I remember wading to the island on a warm sunny day. As a current moved sun-heated water from Harlow Creek and the shallows off the sandy shore over the bar, the temperature of the water was pleasant. I remember the large rock of Jacobsville conglomerate that looks like the back of a whale. I see it's called Lonely Knob on your geologic map. Now I want to go back with my kayak and your map.
Love the detail and deep explanation. It makes it very approachable for me at least despite not knowing much more about geology than finding it interesting. Thanks for sharing your knowledge with us. Much better use of time than most of the videos on here hah.
Ah the Mid continent rift system it was a fascinating feature to learn about, if it wasn't the Grenville which shut it off what did a plume moving too far away? And given how geology tends to reuse geological weak points during future tectonic deformation events what do you think the odds of this structure getting reactivated at some point in the geologic future given how prominent it is as a feature?
One thing fascinating line of evidence for Rodina reconstruction is the linking of sediment grains from sedimentary units of that time to ancient cratonic source rocks to effectively trace out a former river system that crossed from North America into what is now Australia.
I'm not sure if there are other examples where that technique has been used since it requires ancient river deposits of the appropriate age and very distinct zircon source rocks but there is something about tracing a former river system across two continents now on the opposite sides of the planet.
And on the note of zircons it is insane how durable they are with young volcanic rocks from hot spots like Hawaii the Galápagos Reunion Rapa Nui etc. sometimes bringing back up preserved zircons from ancient subducted crust some of which have ages indicating they go back to the Paleozoic if not older. Laboratory simulations and modeling have subsequently revealed that yeah zircons can survive in the upper mantle and then under the right circumstances get brought back to the surface as their source rocks become melted or entrained in magma as Xenoliths. It was apparently discovered by accident in some lava samples from Kilauea which lead scientists to check elsewhere and sure enough there are little bits of these ancient zircons mixed into other young hot spot volcanic rocks without said zircons getting reset.
Some people think part of the rift was successful. I don't think it was. The Grenville is still a viable hypothesis. Personally, I think plume activity elsewhere and preferred rifting on other continents could not maintain the magma chamber(s). So when they ran out, that was it.
Great point about reactivation. The MCR actually was a reactivation...sort of. In the Lake Superior-Huron area, the continent did successfully rift 2.5 Ga. By the time the MCR started, there were some new accretions to North America, one being in the general vacinity. It was already weak. Could it rift here again? It very well could.
Sending lots of love and comfort during your grieving process 🙏❤️🩹
My deepest condolences for your cat. I know how hard that is.
Thank you
It was fun for me to return in memory to Little Presque Isle, which I visited with my son and parents in about 1990. I remember wading to the island on a warm sunny day. As a current moved sun-heated water from Harlow Creek and the shallows off the sandy shore over the bar, the temperature of the water was pleasant. I remember the large rock of Jacobsville conglomerate that looks like the back of a whale. I see it's called Lonely Knob on your geologic map. Now I want to go back with my kayak and your map.
Thanks for the great description! It brings back memories.
A nice geology video to watch on a Sunday afternoon. Thanks for taking the time to make these.
Excited to see follow ups on this topic. You should see the basaltic pot holes of WI/MN by taylors falls.
I am not sure I have been there
Love the detail and deep explanation. It makes it very approachable for me at least despite not knowing much more about geology than finding it interesting. Thanks for sharing your knowledge with us. Much better use of time than most of the videos on here hah.
Thank you for watching!
Would love for you to cover the Reelfoot rift.
That's a thought!
@ 21:28 🎶🎶now I know my ABC's won't you come and sing with me 🎶🎶
My condolences about Lilith.
Thank you!