Boffins find evidence Atlantic Ocean has started closing On November 1st, 1755, the Portuguese capital Lisbon experienced a very nasty earthquake. Up to 100,000 people died and much of the city was destroyed. A Portuguese scientist working in Australia now says the earthquake was caused by an 'embryonic subduction zone' that may split the Eurasian tectonic plate and cause the …
> 'No-Nukes' lobby
So, experts. Science fiction novels have proposed getting rid of nuclear waste by vitrifying it and dropping it into subduction zones, on the basis that by the time the glass has dissolved/disintegrated in a few 10K years it will have been absorbed into the crust and be on its way, harmlessly, to the core.
Is this actually practical? Discuss...
The vitrification part works, West Valley Nuclear had a pilot project for it near Buffalo, NY in Springville to cleanup the leftovers of a failed nuclear fuel reprocessing center. Left a bunch of big black glass logs that could never be trucked to the underground storage in Yucca Flats because hey didn't want it there either.
Unfortunately, we're not close to any subduction zones. Assuming these are close enough to the surface to be useful, it would sound like a great idea.
I assume that Magma can be radioactive considering where it comes from and adding more by dumping the waste may not greatly increase the overall level due to dilution.
Launching it into the Sun would work too but too costly Would deep sea dumping be any less costly?
"It's kinda worrying that he's moved to the other side of the planet .."
Last night's episode of the BBC "Rise of the Continents" was about Australia. How it parted company with Antarctica - leaving the latter at the South Pole cut off from warm seas to support its then lush vegetation.
Australia continues its drift northwards and is on target to crush Indonesia against India - and Japan against China. In the process its deserts will again become the lush vegetation that the fossil records capture.
The current BBC documentary series on plates tectonics is trying to educate the general public, or at least the subset that watches BBC Two or BBC Four. Very slow moving and full of flashy graphics and pretty pictures. It does contain some interesting long views of the way the continents have been formed, and re-formed - plus some of the scientific evidence behind the theories.
Reminds me of our "O" Level Geography teacher in the early 1960s. He told us that it was a coincidence that South America and Africa seemed to be complementary shapes. My memory is that he also said that a "new" theory called "plate tectonics" was not really viable.
"The modern Horizon format makes me weep"
The last Horizon that I couldn't snooze through was at least a decade ago. That was the one about the human condition where cartilage turns to bone - especially if it is cut in an operation. Miss a second and you missed an important step in the development of the story.
The "Continents" program would have been much improved if the graphics had been less detailed and shown for longer so one could appreciate exactly what was happening. The content was interesting - but included too many irrelevant "human interest" scenes. That particular presenter's style puts me off - although in fairness that may have more to do with the programme's production team.
Science was interesting to us as kids for its own wonders - not for being dressed up with irrelevant bystanders' antics.
Subduction doesn't mean the ocean is closing, only that some of the oceanic lithosphere has become cold enough and old enough to lose most of its bouyancy. The Atlantic will only be in trouble once its spreading ridge is subducted; a similar thing has happened the East Pacific Rise under the Western United States which is why the ground there is - stretchy.
The Atlantic is going to more closely resemble the Indian ocean which is still opening and doing a splendid job of (amongst other things) building the Himalayas, but there is active subduction of its crust at Makran under Pakistan, under the Indonesian Arc and in and around Vanuatu. There's also a region to the South of New Zealand, the Macquarie Fault Zone, where subduction appears to be starting, much like what is going on under Portugal right now.
"Newly-appearing subduction zones are, Dr Duarte added, to be expected as part of Earth's “super-continent cycle” that sees much of earth's land come together in very large continents..."
And here I thought the continents were moving apart since the days of Gondwanaland and Pangea...
"And here I thought the continents were moving apart since the days of Gondwanaland and Pangea..."
There is a limited pool of ocean in which they can move. The up-welling magma flows find weaknesses that split the larger pieces apart - and then they have to go somewhere. Like a multi-player game of pong - in very slow motion - they keep colliding with each other.
As someone above rightly said the BBC Horizon format is on a time rack - but the "Rise of the Continents" does contain some interesting nuggets about this phenomenon. If they had cut out the glossy images then they could have made a good single programme covering the meanderings of all the continents.
Pangaea was just the latest in a series of supercontinents. It was made by assembling Gondwana (pedant note: you don't need the 'land' since Gondwana means 'land of the Gonds') which is a borderline supercontinent of its own as well as Laurentia, Baltica and Siberia.
Before that there was Pannotia around the 0.6Gy mark which is associated with the Pan African Orogeny that created the modern African continent, that followed the surprisingly long-lived Rodinia (1.25-0.75Gy) that contained pretty much everything apart from the Kalahari and the Congo craton.
Prior to that things get a bit hazier because the magnetic records of rocks have largely been overprinted by later orogenies. The Columbia (Nuna) supercontinent around 1.8-1.5Gy is highly likely to have existed - odd place - eastern India docked to where California would be and Australia neighbours with Canada.
Further back there is Kenorland which seems to be associated with diamonds and iron formations between 2.7Gy and 2.0Gy, and the hazy Ur that work in South Africa and Australia suggests might date as far back as 3.6Gy. But at that point the geology is getting seriously buggered and whilst it is possible to work out the sort of processes that were going on (a mix of modern subduction and weird buckling of continents), it's almost impossible to relate the continental fragments to one another.
"collision of African and Eurasia has just about run its course, having already spawned the band of mountains from Gibraltar to the Himalayas"
Surely the African impact on Europe didn't have that much effect on the Himalayas? That was surely caused by the Indian plate barrelling up into the midrift of Eurasia like an over enthusiastic puppy into the crotch of a bishop?
Having chucked Africa and India into Eurasia those sticky mantle currents will presumably find another way to transfer their momentum to the surface scum. I suppose the action near Lisbon might be a case of crumpling as the Atlantic pushes the combined mass to the right while the opening of the Red Sea pushes Africa to the left.
On the other hand I seem to recall that there are a number of features that start down the road to being plate boundaries but never actually get there.
The African collision is responsible for everything from the Atlas Mountains through the Alps and Carpathians to the massive deformation of the Aegean Sea. Further East it is Arabia which is crunching into Europe along the Zagros. Until recently (say 30My) Arabia was part of Africa, but it has now become a separate plate by the emplacement of the Afar Mantle Plume under the Southern Red Sea where a new constructive margin has formed.
The Himalaya are the result of India whacking into Eurasia at 20cm pa (nice analogy of yours by the way).
Mantle currents don't seem to directly drive continental movements. Much more important are vertical displacements - such as dynamic uplift of continents over hot Mantle plumes which cause material to slide sideways towards lower elevations (such as is happening in the African Rift, the Western United States and Central China), and, at the other end of the process, the subduction of dense material into the Mantle which drags ocean crust after it.
Then we should proceed with my plan to move Great Britain to the safety of the Mediterranean post haste.
Stage 1: Build a new motorway carving a straight line from Lands end to john o groats.
Stage 2: load Scotland into dumper trucks, use the rubble to build a causeway into the sea at lands end.
Stage 3: Snake causeway around France and through the straights of Gibraltar consuming GB from the top down as we go.
Stage 4: create a new donut shaped landmass in the Mediterranean, effectively annexing the entire sea.
Stage 5: Relax on the beach for a job well done, txt 'told you so' to Norway as they sprout volcanos.
"Then we should proceed with my plan to move Great Britain to the safety of the Mediterranean post haste."
It seems a shame to bury all that beautiful scenery into the foundations of the causeway. I think we should move Slough and Crewe first then any town/city in which Katie Price or Simon Cowell live. We should then move onto the homes of any BMW/Audi drivers and Rupert Murdoch.
We can melt down windfarms to make pontoons and the hole left by the removal of Slough would become my first giant shark tank adjacent to my newly built mansion. Now all I need is a white pussy-cat....
Where is the icon for Not Joking? The 1755 Lisbon quake caused a tsunami in which "great loss of life and property occurred upon the coasts of Cornwall". The new subduction zone is active and growing so the next quake could come along any time now. The UK (and presumably also France & Ireland) is at genuine risk of a serious tsunami.
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