Stage 1 of #TheWilsonCycle in action at the link below.
https://bird.makeup/users/rainmaker1973/statuses/1633878381136855041
More on the Shanxi Rift System here: https://en.m.wikipedia.org/wiki/Shanxi_Rift_System
#TheWilsonCycle #ShanxiRiftSystem #SupercontinentCycle #geology
Wilson Cycle Phase 4 - Episode 4 - Collision and Collapse
“Tuzo was indeed an amazing man. His scientific interests were in the building of mountain ranges and moving of continents, and he certainly had a huge and long-lasting effect on Earth Science. But even more, his talent was in moving another type of mountain: those ideas in men’s and women’s minds that lock us into past patterns of behaviour and prevent visualization of new possibilities.”
~ Gordon F. West and others, from “John Tuzo Wilson: a man who moved mountains.”
‘The final stage of the Wilson Cycle involves continental-continental collision and the formation of giant mountain belts. And yet it’s how these giant mountain belts get exposed at the surface that allows us to study the Wilson Cycle in its entirety. Now we are going to explore the rocks which are formed deep within the mountain building stages of the Wilson Cycle and discover how these rocks are exposed at the surface today.
~ Professor Dougal Jerrom - intro to Episode 4
In the video below, “Wilson Cycle Phase 4 -Episode 4 -Collision and Collapse”, we finish our trip with Professor Dougal Jerrom, and the team of researchers in search of evidence for the collision and collapse of the Caledonian orogeny in the Caledonides Mountains. This series has kept the last and best for the finale, and it is a mind-blowing conclusion. I really recommend you watch the 29 minute video for yourself. It is well worth your time!
We first stop to look at some eclogites, and Norway has the best in the world - “the jewel in the crown of Norway” and are under its protection. These are ultra-high pressure metamorphic rocks that have been formed 100 km. or more deep in the subduction zone, and are especially stunning with coarse-grained “pegmatic” texture, deep green orthopyroxene, bright red garnet, and a white mineral coesite, a metamorphic index mineral indicates they underwent extremely high pressure. As Professor Jerrom says, discovering how these rocks were exposed is one of the most fascinating geology stories yet.
This starts with the subduction of oceanic crust underneath oceanic crust. The subducted slab is being pulled down by its own weight, and the two continents are approaching each other. The upper portion of the slab is still buoyant (see the model below, and the model in the video they run in the CEED lab) and doesn’t want to go down, so the slab breaks off and sinks through the mantle. The upper slab springs back up in a process called “eduction” (the reverse of subduction) and brings the deep metamorphic rocks back up where they are exposed during the collapse portion of the Wilson Cycle.
The late stages of subduction and collision build mountains as high as 3 km., but they are gravitationally unstable. The crust is thickened and getting heavier, and the upper level goes back into extension even as the lower crust is still thickening because of its own weight. This happens EVEN AS MOUNTAIN BUILDING IS STILL OCCURRING. Lots of erosion fills the basin with thick sediments up to 25 km. We see a giant detachment fault that is slowly denuding the top of the mountain of sedimentary rock that is sliding down a fault plane of metamorphosed rock. So mountains can quickly (in geological time) be stripped and the deeper crustal rocks exposed by isostatic rebound. We see this happening to day in the Himalayas Tibetan Plateau.
We are taken up close to a “textbook” active detachment fault with gouge, grain-size reduction, and fluid circulation. By studying the magnetism of the fractures of the fault and comparing it with the magnetism in this part of the world, tells us that the fault was reactivated, and also tells us about the end of the Caledonian, and the beginning of a new Wilson Cycle!
“So we’ve seen all the gems of knowledge stored in the rocks of Norway from the mountains to the fields tell us about this major cycle in Earth’s history, but it doesn’t end here because it’s happening again today with the north Atlantic opening and Norway is the place we could come back to in millions and millions of years in the future to understand the closure of that ocean and the mountain building event that would form the next Wilson Cycle.’
~ Professor Jerrom Dougal closes the series.
Wilson Cycle Phase 4 - Episode 4 - Collision and Collapse: https://youtu.be/pFuW4MtXhIM
The video introduces a paper published in the 90s that outlines the process of subduction and eduction, by Torgeir B. Anderson (yes, the same Torgeir that has been providing all the information on our journey) et al. Highly informative https://www.researchgate.net/publication/229872945_Subduction_and_eduction_of_continental_crust_major_mechanisms_during_continent-continent_collision_and_orogenic_extensional_collapse_a_model_based_on_the_south_Norwegian_Caledonides
#JohnTuzoWilson #LegendsOfGeology #TheWilsonCycle #Caledonides #Norway #WatchTheDamnVideo #PlateTectonics #SubductionAndEduction #OrogenicCollapse #eclogites #geology #Science #NorwegianGeologyRocks @geology
Wilson Cycle Phase 3: Ocean Closing
“I enjoy, and have always enjoyed, disturbing scientists.”
~ John Tuzo Wilson
“From great oceans, giant mountains will form. This is the prediction of the third phase of the Wilson Cycle where we see the closure of the vast oceans like the Iapetus Ocean, and the formation of continent to continent collision mountains.”
~ Professor Dougal Jerrom, intro to Wilson Cycle Phase 3: Ocean Closing video linked below
In the 24 minute video below (a great watch), we continue our travels with Professor Dougal Jerrom of Oslo University, to look at evidence of the closing of the former Iapetus Sea in the Caledonian of Norway. The video starts with a nice recap of the other videos.
Whenever there is an ocean closure, geoscientists always look for ophiolite. Ophiolites in the geologic record provide evidence of subduction zone tectonics. We have already seen the pillow basalts, sheeted dikes (gabbros) and peridotites that form ocean crust in earlier videos in this series. An ophiolite is then a bit of oceanic crust that got swept up in the continental collisions and provides the first proof of an ocean closure.
Next we learn about melange - the sediments that were scraped up during subduction, also known as an accretionary wedge. There are also remnants of the island arc formed during subdution all accreted between the bits of continental crustal blocks that eventually collided.
Enjoy the video below where you see glimpses of the geology of the beautiful Norwegian Caledonian.
Wilson Cycle Phase 3: Ocean Closing: https://youtu.be/jYlQCbDmEVw
More on the closing of the Iapetus Sea here: https://en.m.wikipedia.org/wiki/Iapetus_Ocean
Includes Step 5 of the Wilson Cycle: https://c.im/@vickyveritas/10962360456...
Refer to this great labeled diagram of the Wilson Cycle for the components of the ocean closure and continent to continent collision and mountain building: https://c.im/@vickyveritas/109628513962823739
Note: We will see the last steps of the Wilson Cycle, the continent to continent collision and the formation of giant mountain belts, and the great grand finale of this series. Stay tuned.
#JohnTuzoWilson #TheWilsonCycle #Caledonides #IapetusOcean #Norway #PlateTectonics #Ophiolite #AccretionaryWedge #granites #SutureZones #Laurentia #Baltica #geology #ScienceMastodon #NorwegianGeologyRocks @geology
Wilson Cycle Phase 2: Ocean Opening
“…for times before the present oceans existed, we cannot do plate tectonics. Instead we must consider the life cycles of the ocean basins.”
~ John Tuzo Wilson
In the 12 minute video below (a great and quick watch), “Wilson Cycle Phase 2: Ocean Opening”, we continue our travels with Professor Dougal Jerrom of Oslo University, to look at evidence of the former presence of oceanic crust.
The first evidence we find is the presence of pillow basalts formed in the deep ocean. Pillow basalts are erupting magma that is quenched (hardened) by the ocean water. The scientists can tell that the ocean was deep because the pressure of the water allowed the gases to be released in solution (no vesicles in the basalt). Pillow basalts are the top layer of oceanic crust.
Secondly we find evidence of a black smoker in a copper mine. The black smoker was created by hydrothermal activity, as evidenced by the presence of copper and other minerals, in the sheeted dikes, the second layer of oceanic crust.
Wilson Cycle Phase 2: Ocean Opening: https://youtu.be/AtflMez-Zb4
Includes Step 3 and 4 of the Wilson Cycle: c.im/@vickyveritas/10962360456...
Note: We will see the other steps of the Wilson Cycle in this series. More to come!
#TheWilsonCycle #Caledonides #Norway #PlateTectonics #geology #PillowBasalts #SheetedDikes #BlackSmoker #HydrothermalActivity #ScienceMastodon #NorwegianGeologyRocks @geology
Wilson Cycle Phase 1: Rifting
“These two mountain ranges are really one and the same – except that they are now separated by the Atlantic Ocean, which cut the range in two at a low angle when it opened between them. At one time the two belts had been joined, end-to-end, Caledonides in the north, Appalachians in the south…”
~ John Tuzo Wilson, “Did The Atlantic Close And Then Re-Open?” Nature, Vol. 211, No. 5050, August 13, 1966
Rifting of the enormously long mountain chain ended up with parts in both North America (Appalachians) and Norway (Caledonides), among many other places. Geologist and Geophysicist John Tuzo Wilson reconstructed the multi-phased tectonics to trace the earlier proto-Atlantic Ocean that closed, and today’s Atlantic Ocean that opened through the processes that are named for him: The Wilson Cycles.
In the video below, “Wilson Cycle Phase 1: Rifting”, we travel with Professor Dougal Jerrom of Oslo University, and researchers from the Centre for Earth Evolution and Dynamics (CEED) who take us back 450 million years, and into what was once 90 kilometers deep in the Earth’s crust to the Caledonian rocks of Norway that tell us about the biggest cycle on Earth. Don’t miss the video which gives a voice to the rocks that record our dynamic Earth and the Wilson Cycle.
Wilson Cycle Phase 1: Rifting: https://youtu.be/WAGFSf8gqfg
Includes Step 1 and 2 of the Wilson Cycle: https://c.im/@vickyveritas/109623604569764070
Note: We will see the other steps of the Wilson Cycle in this series of videos. More to come!
#TheWilsonCycle #Caledonides #Norway #PlateTectonics #geology #peridotites #turbidites #tillites #conglomerates #ScienceMastodon #NorwegianGeologyRocks @geology
The Wilson Cycle Illustration: No Rock is Accidental
I had to share this much better picture of the Wilson Cycle with a volcanic island arc and double subduction. All the details are beautifully labelled. Gorgeous work, and the Wilson cycle still fits.
Recap on Wilson Cycle: https://c.im/@vickyveritas/109623604569764070
#TheWilsonCycle #Rocks #geology #subduction #ScienceMastodon @geology
