What happens when an unstoppable force meats two unmovable objects? Well, in the world of geology there should be volcanism.
A few weeks ago, I was asked by a person who did not believe in science this specific question. “If plate tectonics are real, why then are there no volcanoes in Norway?”
It is a jolly good question from a science refusing flat earther. Because there should be a lot of volcanoes in Norway. Time to answer the question: Why are pyroclastic flows not pining for the fiords of Norway?
The unstoppable force is obviously the Mid Atlantic Rift (MAR) in general and specifically Iceland. The two unmovable objects are the two largest tectonic plates on Earth, the North American Plate (NAP) and Eurasian plate (EAP).
At least the NAP and the EAP should be unmovable, but they are not. About 14 million years ago the started to spread apart, even though simple mechanics says that they should be moving towards each other.
We do know the rough date for two different reasons. One is the trail of calderas across the snake river plane that has done a horse-shoe shaped U-turn with the trail leading to todays Yellowstone. In Norway at that time a very prolonged time of uplift started, so far, the country of lusekofter, goat-cheese and people on skis has uplifted an astonishing 1000 meters.
So, what else happened 14 million years ago? Well, Iceland did. At that time the high-rate volcanism at Iceland started, and a mantleplume started to form from the surface of the mantle burrowing ever deeper.
After a while this started to buckle the earth and a dome formed under Iceland lifting it up 54 meters. And gravity being what it is, the newly formed land started to slide down this bulge.
And since we are talking about oceanic crust it should be quite happy with sliding down under the Baltic Shield and Scandian Craton. And in the beginning it looked like it would do that since the EAP did not change trajectory immediately like the NAP did.
West of Norway a depression started to form called the Norway Through, it ended up being two kilometres lower than the surrounding seafloor, and towards Norway it has a nice subduction like profile.
This buckling depression caused a simple effect with far reaching consequences, because if one place is pushed down, another must rise. And in this case the area being uplifted is a large portion of Norway.
In the end this buckling will cause a break in the oceanic crust and a mega-thrust fault will form as subduction starts. This has not yet happened, and it will take quite a bit of time since the oceanic crust is buckling against the Scandian Craton, the worlds second oldest piece of continental crust.
Not only is it old, it is also unusually cold, hard and deep. To further complicate things it has also been reinforced by massive iron intrusions. Think of it as concrete with massive amounts of rebar. In other words, it will take the depth and angle of the Marianas Deep before it starts to subduct.
There is though a second part of the story to why it will take time before subduction starts. And that is that Iceland is happily pushing the EAP to the ENE. A large portion of the push exerted by Iceland is taken up by this motion. It has also started to move the Scandian Craton in a slightly different trajectory going NE.
This last part has caused strain to build up between the Scandian Craton proper (Norway and Sweden) and the Fennian part (Finland and the Kola Craton) of what is called the Baltic Shield. The end result of these two slightly different trajectories is that a transform fault has formed between northern Sweden and Finland.
The movement along this transform fault is not that large, just a few millimetres a year, but if Iceland remains active the pace will pick up over time and the Scandian Craton will be pushed north of Russia.
This movement have other effects, for one it causes southern Sweden, Denmark and northern Germany to sink. It has also had dramatic effects on the Sea of Bothnia where parts are being pushed up (the High Coast).
Now, why is this interesting? Well, The Baltic Shield has looked the same for as long as we have had continents, every single supercontinent for the last two billion years have had the Baltic Shield staying the same.
It has just been to strong to be broken up, until Iceland came into being that is. It has cracked the uncrackable safe open. But now we need to get back to those lost Norwegian volcanoes.
The volcanoes of Norway
Now that we have learned that we will have to wait for quite some time for subduction to start under Norway, if ever, it sounds like the Norwegian volcanoes will not happen. But, that is not the case.
As Norway is pushing upwards it is causing decompression melt intruding as a crustal delamination at depth, or the formation of a large magmatic body under the crust. It is unclear which of the two is the case, with a high probability that both are happening at the same time.
We can see this enormous body of magma clearly on tomographic imagery. Even though the uplift is minute per year (1cm every ten years), the area is so large that the total amount of magma flowing in is between 5 to 10 cubic kilometres a year.
This buoyant hot liquid is ever so slowly burrowing its way upwards to the surface. It still has quite some ways to go, but sooner rather than later it will arrive to the surface, and the effect would be rather stupendous as it happens.
Even if only 10 percent of the available magma would be released it would conservatively amount to seven million cubic kilometres of lava pouring out. That is a lot of lava pining for the fiords. The end result would be something like the 2-million-year cyclic ignimbrite flare-ups at the Altiplano-Puna Volcanic Complex. Whenever it happens I would not want to be around Norway, but it is obviously quite some time into the future.
The distant future
In the end the backends of NAP and the EAP will be locking together and their respective motion will stop as they turn into a single large unmovable block. That is the moment that subduction will start to take place under Norway. This is roughly 1 million years into the future.
What we have not talked about is the North American side of the Icelandic push-train. Interestingly there is a corresponding action occurring there with large amounts of magma residing under New England and the Southern Canadian Atlantic Coast.
The continental crust here is an easy pushover compared to the steel reinforced behemoth of the Scandian Craton. This means that the onset of volcanism here is closer, but if that will happen in 10 000 years’ time, or in 1 million years is unclear.
This model has quite a few uncertainties in it. How far NE can the Scandian Craton go is the main one. But in the end this has some real world ramifications for the present. For instance building codes in the Northern half of Sweden will have to start to incorporate earthquake proofing. The same goes for Norway.
Currently the Swedish historic decadal earthquakes are ranging up into M4.5, but there are geologic evidence for millennial earthquakes ranging up into the M6 range with centennial M5 range earthquakes. The figures for Norway are roughly the same, but the earthquakes are a bit larger, but further out into the sea. So, any destruction would be roughly the same.
Those dreaming dark dreams about seeing Norway and Sweden being blown towards Saturn, or New York being covered by ash will have their dream fulfilled, but on a timescale that makes their dreams into a moot point.
Personally, I find the idea that something so massive and hard as the Baltic Shield being able to break up due to Iceland to be immensely satisfying. But, I love all sorts of esoteric knowledge.
On a completely different tack, plate tectonics is the best proof that the earth is indeed a sphere. The flat earthers believe that Earth is a round disk. But, if that was the case plate tectonics would either have started at a very slim disk over the equator, or if it was round to begin with it would have become quite fat around the equator by now. And the evidence for plate tectonics is just everywhere in nature to be found.
Another thing that no flat earther has been able to answer is how volcanoes form on a thin coin. Where is the magma coming from? Problem with the flat earthers is that they do not understand that to prove their theory they would have to replace all sorts of science with alternative and better theories. And that in scientific fields they have never even heard of.
And while I am heckling them, I have a final question for them. Why have not a single one of them bought an airplane and flown it due west along the equator? After all, that would prove their theory as they fell off their coin-world.
But, I guess their fevered minds would come up with some mysterious ad-hoc theory as they after a while landed at the point they started from. After all, they are impervious to basic logic and learning.