An international team led by scientists from the Dublin Institute for Advanced Studies (DIAS) has discovered that large portions of the tectonic plate, or lithosphere, beneath Africa have disappeared over the past 200 million years. Their findings have been published in the journal Nature Communications this month.
The team employed seismic tomography – a technique that uses seismic waves propagating from earthquakes around the world – and obtained a detailed three-dimensional model of the lithosphere beneath Africa as it is today. They then used diamonds to get a glimpse into the structure of the lithosphere in the past.
Explaining their work and its significance, Professor Sergei Lebedev of DIAS, said: “These ancient, thickest parts of the African continent had been stable since their formation over 2.5 billion years ago. In view of this remarkable stability, their recent demise is a surprise.
“Diamonds played a key role in our discovery: diamonds come from deep within the thickest tectonic plates on Earth. With them, they bring evidence of catastrophic destruction of some of these plates.
“Diamonds are brought to the surface of the Earth by volcanic eruptions that originate within thick continental plates at depths of over 150 kilometres. This is where diamonds are stable. At depths shallower than 150 kilometres, the pressure is too low and the carbon atoms that make diamonds arrange themselves differently, making graphite instead. Diamonds thus tell us that, at the time of their eruption to the surface, the tectonic plate at that location was well over 150 kilometres in thickness: typically, 200-300 kilometres.”
Missing material 10 times the volume of the Tibetan Plateau The lead author of the paper published in Nature Communications, Dr. Nicolas Celli of DIAS, said: “To our surprise, seismic tomography revealed thin lithosphere in many locations in Africa, including South Africa, Angola and Tanzania, where it used to be thick only 30 to 200 million years ago, according to diamonds. This implies that the plate in these locations got much thinner, by at least 100 kilometres, during the last 200 million years. The volume of the missing tectonic plate material is as much as 100 million cubic kilometres, over 10 times the volume of the Tibetan Plateau.”
Explaining the likely trigger for such catastrophic thinning of the lithosphere, Professor Lebedev said: “This was probably caused by the impact of hot upwellings from the Earth’s core, known as mantle plumes. The plumes have long been thought to be responsible for cataclysmic volcanic eruptions that create so-called large igneous provinces and cause mass extinctions. In Africa, the locations of the newly discovered lithosphere loss and those of the large igneous provinces coincide. This indicates that mantle plumes were the cause of both.
“As tectonic plates slide past each other and continents drift along the surface of the Earth, the convective mantle plumes rise from below and strike the bottom of the plates. Our new findings imply that the fate of each ancient core of a continent depends, to a large extent, on its luck in dodging the mantle plumes.”
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DIAS scientists discover disappearance of large parts of tectonic plate beneath Africa
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Last Updated: 13th January 2020 by Caoimhe Mulhall
An international team led by scientists from the Dublin Institute for Advanced Studies (DIAS) has discovered that large portions of the tectonic plate, or lithosphere, beneath Africa have disappeared over the past 200 million years. Their findings have been published in the journal Nature Communications this month.
The team employed seismic tomography – a technique that uses seismic waves propagating from earthquakes around the world – and obtained a detailed three-dimensional model of the lithosphere beneath Africa as it is today. They then used diamonds to get a glimpse into the structure of the lithosphere in the past.
Explaining their work and its significance, Professor Sergei Lebedev of DIAS, said: “These ancient, thickest parts of the African continent had been stable since their formation over 2.5 billion years ago. In view of this remarkable stability, their recent demise is a surprise.
“Diamonds played a key role in our discovery: diamonds come from deep within the thickest tectonic plates on Earth. With them, they bring evidence of catastrophic destruction of some of these plates.
“Diamonds are brought to the surface of the Earth by volcanic eruptions that originate within thick continental plates at depths of over 150 kilometres. This is where diamonds are stable. At depths shallower than 150 kilometres, the pressure is too low and the carbon atoms that make diamonds arrange themselves differently, making graphite instead. Diamonds thus tell us that, at the time of their eruption to the surface, the tectonic plate at that location was well over 150 kilometres in thickness: typically, 200-300 kilometres.”
Missing material 10 times the volume of the Tibetan Plateau
The lead author of the paper published in Nature Communications, Dr. Nicolas Celli of DIAS, said: “To our surprise, seismic tomography revealed thin lithosphere in many locations in Africa, including South Africa, Angola and Tanzania, where it used to be thick only 30 to 200 million years ago, according to diamonds. This implies that the plate in these locations got much thinner, by at least 100 kilometres, during the last 200 million years. The volume of the missing tectonic plate material is as much as 100 million cubic kilometres, over 10 times the volume of the Tibetan Plateau.”
Explaining the likely trigger for such catastrophic thinning of the lithosphere, Professor Lebedev said: “This was probably caused by the impact of hot upwellings from the Earth’s core, known as mantle plumes. The plumes have long been thought to be responsible for cataclysmic volcanic eruptions that create so-called large igneous provinces and cause mass extinctions. In Africa, the locations of the newly discovered lithosphere loss and those of the large igneous provinces coincide. This indicates that mantle plumes were the cause of both.
“As tectonic plates slide past each other and continents drift along the surface of the Earth, the convective mantle plumes rise from below and strike the bottom of the plates. Our new findings imply that the fate of each ancient core of a continent depends, to a large extent, on its luck in dodging the mantle plumes.”
The Nature Communications paper is available at: https://www.nature.com/articles/s41467-019-13871-2.
Category: DIAS, Featured Blog Posts, Geophysics, Geophysics Section News & Events, News
The final #Syngeweek part is now live on our website. "Yet meet we shall, and part and meet again Where dead men meet, on lips of living men." dias.ie/2020/03/23/syn… Returning visitors don't forget to clear your cookies! #DIASdiscovers
Today is the 25th anniversary of the passing of Professor J.L Synge. Part 6 and the final #SyngeWeek installment will go live this evening on our website at 6pm #DIASdiscovers
What a great idea! 👩🚀👩🚀 twitter.com/SpaceStnExplor…
#SyngeWeek Part5 is now live on our website! "One of the attractions [of coming to DIAS] for me in 1948 was the prospect of being a colleague of Schrödinger. " Read more: dias.ie/2020/03/23/syn… Returning visitors remember to clear those cookies! #DIASdiscovers
Part 5 of #SyngeWeek covers his career with DIAS, the publication of "Relativity:The General Theory" which made DIAS the leading centre for research in General relativity for the following decade. Part 4 is availble until 6pm: dias.ie/2020/03/23/syn… #DIASdiscovers
On tonight! Don't miss your chance to see this fascinating documentary about Schroedinger's time in DIAS and the seminal discovery it lead to. Not forgetting he was DIAS' first Director of Theoretical Physics. @RTEOne #DIASdiscovers #schrodinger
Returning Visitors please remember to clear those cookies!
"...sometime early in 1944, I got a phone call from Oswald Veblen, asking me whether I would like to go to Europe attached to the American Army in a scientific capacity." #SyngeWeek Part 4: Columbus & Europe is now live on our website ➡️ dias.ie/2020/03/23/syn… #DIASdiscovers
Spring Newsletter just launched! See what has happened in 2020 so far: mailchi.mp/5ea85f227dce/d… Subscribe to our mailing list today to get future editions direct to your mailbox: dias.ie/mailinglistsub… #DIASdiscovers
"...he wanted to endow international medals in mathematics (a subject omitted from Nobel Prizes, on account of Nobel's jealousy of Mittag-Leffler..." #SyngeWeek Part 3: Toronto-Dublin-Toronto dias.ie/2020/03/23/syn… Returning visitors please remember to clear those cookies 🍪
"Long before 1916 I had become a Nationalist, but the idea that there might be an armed rebellion was nothing more than a whispered rumour..." #SyngeWeek part 3 will be posted on our website this evening at 6pm. Part 2: University is available until then: dias.ie/2020/03/23/syn…
Please note the reopening date of DIAS buildings is now 20 April. dias.ie/2020/03/13/ale… #coronavirus #StayHomeSaveLives
#SyngeWeek Part Two: University, is now live on our website. "...could force the rifle down the leg of his trousers, and we set out through the Front Gate of College; " ➡️dias.ie/2020/03/23/syn… Returning visitors please be sure to clear those cookies🍪 #DIASdiscovers
#SyngeWeek part 2 is coming this evening. This will cover his University years. J.L. Synge, an Irish mathematician & physicist, whose seven decade career included significant periods in Ireland (& DIAS) Canada, and the USA. Part 1 ➡️ dias.ie/2020/03/23/syn… #DIASdiscovers
"My mother was Ellen Frances Price (1861-1935), daughter of James Price, a distinguished Irish engineer. I believe that, in so far as it was genetic, my interest in mathematics came from this side of the family."- J.L Synge More: dias.ie/2020/03/23/syn… #SyngeWeek #DIASdiscovers