When you purchase through connectedness on our website , we may earn an affiliate commission . Here ’s how it works .
In the twilight of the Cretaceous , 86 million year ago , a volcanic fissure in what is now South Africa rumbled to life story . Below the Earth’s surface , magma from hundred of miles down shot up as fast as a car on the autobahn — if that car were barreling through satisfying rock — chewing up rocks and minerals and carrying them toward the surface in a reverse avalanche .
What this looked like on the surface is recede to story , but it may have been as dramatic as the irruption of Mount Vesuvius . What it leave behind was a series of carrot - shaped , igneous - stone - fulfil tubes under low , weathered ashen hills .
Diamonds erupt at the surface of the planet when supercontinents break up. Studying these sparkly gems can reveal secrets about our planet’s deep history.
In 1869 , a shepherd ’s find of a huge , scintillating rock on a nearby riverbank would catapult this unassuming landscape into infamy . The stone was an enormous rhomb that would eventually be cognise as the Star of Africa , and the white hills hid what would become the Kimberley Mine , the epicentre of South Africa ’s infield rushing and quite mayhap the largest hole on Earth ever excavate out by hand .
Thanks to the Kimberley Mine , often called " The Big Hole , " the formation wherediamondsare found are now sleep with as kimberlites . The formation are sprinkled across the Earth , fromUkraine to Siberia to Western Australia , but they ’re comparatively belittled and rarified . What makes them special is that their magma come from very deep down . There are still questions about precisely how cryptic , but they are get it on to rise from beneath the fundament of continents at the borderline of the hot , convecting mantle . Some may start even deeper , at the transition between the upper and dispirited mantle .
Related : What ’s inside Earth ?
In 1869, a shepherd in South Africa discovered a giant diamond in the hills, and the Kimberley Mine was born. The mine has since closed and the “big hole,” possibly the largest hole ever dug by hand, is filled with water.
As such , these magma tap into very abstruse , very ancient rock ‘n’ roll , and they interact with other processes that occur only in the deep Earth — namely , the organisation of diamonds . To crystallize plain - old carbon paper into firmly , sparkly diamond necessitate dandy pressure , so these gems form at least 93 miles ( 150 kilometre ) down , in the deep layer of the lithosphere , the scientific full term for the crust and relatively fixed upper blanket . Some , known as sub - lithospheric diamonds , form even deeper , down to around 435 mile ( 700 km ) . kimberlite , on their eruptive journeying to the surface , arrest diamond and embroil them into the upper cheekiness , delivering them relatively whole and sometimes even containing pocket of fluid from the pall itself .
Researchers have long known that as architectonic plates grind under one another , they cart down carbon from the open to deepness where it can crystallize into diamond . Now , they ’re take off to see that what goes down must ( sometimes ) come up , and that this reappearance of carbon — now press into glittering gems — is also attach to the movements of tectonic plates . In particular , diamond seem to erupt when supercontinents break apart .
" While these are different processes , together the diamond and kimberlite can inform us about the life bike of supercontinent times , " saidSuzette Timmerman , a geologist at the University of Bern in Switzerland who studies diamonds .
Kimberlites form at the base of continents and as they rise quickly, they catch deeper-formed diamonds and drag them to the surface through kimberlite pipes.
Coming to the surface
No one has ever seen a kimberlite eruption at first hand . There have been very few in the past 50 million year , and the most late possible eruption , in the Igwisi Hills of Tanzania , occurred over 10,000 years ago . Not only that , but the primary cloth in kimberlite , the mineral olivine , weather condition away quickly on the aerofoil , saidHugo Olierook , a research associate at Curtin University in Australia .
This makes study kimberlites challenging . Scientists are perplexed , for lesson , about the chemical science of the original germ of the melted rock music in the cape , as well as about how kimberlites manage to punch through the stable heart of what geoscientists call " cratons " — the thick internal parts of continent that usually resist kerfuffle .
A handful of recent studies are adumbrate out a raw account for why this happens . The first clue is time . It ’s long been noted that pulse of kimberlite activity seem to correspond with the near timing of supercontinent breakage - ups , saidKelly Russell , a volcanologist at the University of British Columbia in Canada . A2018 studyled bySebastian Tappe , a geoscientist at The Arctic University of Norway , strike a world smell at this coincidence of timing and encounter that it up : There was a stiletto heel in kimberlite eruption around the breakup of the supercontinent Nuna some 1.2 billion years ago to 1 billion class ago .
Instabilities form at the edges of continents but migrate toward the hearts of the “cratons” over millions of years.
Another heart rate occurred between 600 million and 500 million years ago , coinciding with the breakup of the supercontinent Rodinia , consort to the 2018 inquiry , espouse by a pocket-size pulse between 400 million and 350 million years ago . But the most fertile period , accounting for 62.5 % of all known kimberlites , occurred between 250 million and 50 million yr ago . That range happens to coincide with the separation of the supercontinentPangaea . To some investigator , this suggests that supercontinent cycles are all important for kimberlite eruptions .
" The breakup of these Continent are rudimentary to getting these diamonds up from these recondite depths , " Olierook told Live Science .
Olierook and his team recently study the ages of strange pink diamonds from a shaping in westerly Australia and find they likely came to the surface about 1.3 billion twelvemonth ago , within the windowpane of Nuna break up . The Modern discovery links diamonds to the stretching of continental crust , Olierook said .
The rough Cullinan diamond, the largest known gem-quality rough diamond, was pulled from the Kimberley Mine in 1905. Diamonds like these can come from deep inside Earth and reveal billions of years of the planet’s history.
" It ’s those extensional forces that allow those little pocket of cryptical - seat magma to rise to the top , " he suppose .
The march of the kimberlites
The knavish question , though , is how this happens . To get a kimberlite , there are two central ingredients : deep , melted rock rich in fluid , and a continental disruption that may bring that melt to the surface . No one bang what causes the establishment of the kimberlite melt , but the chemical science of kimberlites is very different from that of the mantle stone it melts from . Kimberlites are also rich in volatiles such as water and C dioxide , which is what makes them so perky and high - velocity . They shoot through the crust like Champagne rushing through an uncorked bottle , ascend at up to 83 miles per hour ( 134 km / h ) . For comparing , the magmas that flow out of the volcanoes in places like Hawaii max out at around 13.5 mph ( 21.7 km / h ) .
An August 2023 sketch used computer moulding to calculate out howkimberlites can burst through the thick heart of continents . The researchers constitute that the process of rifting , in which continental crust pulls apart , was primal . The stretch create peaks and valley at both the surface and base of the continent . At the base , these jagged edges permit lovesome mantle materials to rise , and then nerveless and fall , creating eddies . These twist mix materials from the bag of the continents , take in the frothy , floaty kimberlite , which can then shoot up toward the control surface , carrying any rhombus they might materialise to run into on their way up .
This mental process began right where the continent was rifting asunder , but mold showed that these erose region of eddy formation destabilize neighboring areas on the craton , creating the same moral force nearer and nearer to the continental DoI . The result was a pattern of kimberlite eruptions starting near the break zone but bit by bit parade into expanse of stable crust . This slow march explains why kimberlite heartbeat do n’t top out until a bit after a big separation begins , saidThomas Gernon , a geologist at the University of Southampton in the U.K. who led the study .
" You will see these peak of kimberlite seem to chance after bounteous supercontinents have broken up , " he enjoin . " But it ’s not just a one - remove thing ; it ’s something that may last quite a long sentence after supercontinent detachment . "
Kimberlites may be quite unwashed at the bases of continents , said Tappe , whose 2018 discipline on kimberlites and supercontinent breakups came to similar conclusions as Gernon ’s . Tappe and his team find that these thaw may have been specially prominent during the dissolution of Pangaea , because the mantle , which has been slowly cooling since Earth solidified , reached just the right temperature around 250 million years ago to have kimberlite - type melts reign . Prior to that period , the stone in that realm may have been too live to get that combination of thaw and volatile cloth that make believe kimberlites so eruptive . This may be one reason why most kimberlite diamond mine date from the breakup of Pangaea .
Messages in a diamond
As the dull , white mound that once track the Kimberley Mine attest , kimberlites themselves ca n’t say much about the mantle where they originated . They brave out away within a few days , misplace much of what makes them interesting on a chemical layer . However , the infield carry within kimberlite are a different story . They have their own constitution chronicle that do n’t coincide with the formation of the kimberlite magma itself . But their hazard meetings hundreds of mi below the airfoil intend that bits of the mantlepiece that would never otherwise see daylight can reach human hands .
These spot are microscopic air hole of fluid from the prison term the diamonds formed . Many of these " inclusions " escort back one C of millions of class , while a few specimenscount their ages in the billions . Plus , some of these diamonds mould very deep in the blanket , so certain stones can carry materials from as far down as the boundary between the mantle and the core .
" Only in kimberlites we can see sample come from 400 kilometers [ 250 miles ] , even down to 2,000 kilometers [ 1,200 knot ] , " saidMaya Kopylova , a prof of diamond exploration at the University of British Columbia . " No other magmas on Earth do that . "
Related : What ’s the deepest - forming stone on Earth ?
While the eruption of ball field can delineate a news report of supercontinent breakup , their constitution may also provide a cue to how continent come together . In a study published in October 2023 in the journalNature , Timmerman learn diamond from Brazil and Guinea that work between 186 and 434 mile abstruse ( 300 to 700 klick ) . By go steady liquid inclusions within the ball field , Timmerman and her colleagues estimated that the diamonds formed around 650 million age ago , when the supercontinent Gondwana was form . The infield probably gravel to the base of the continent and sit there for millennia until Gondwana broke up during the Cretaceous period and kimberlite brought them to airfoil , Timmerman secern Live Science .
What was important about these superdeep diamond , Timmerman said , was that they helped excuse how Continent grow . Supercontinents are build when pelagic impertinence bear on under continental crust . This process , called subduction , tugs two continents on diametrical sides of an ocean nearer together . This same subduction fetch carbon paper to the depths , where it can be compressed into diamond .
Down in the mantlepiece , bits of these subducting plates can become perky and go up back up , comport superdeep diamond with them , Timmerman explained . This material may stick to the bases of continent for millennia , helping them rise from below . It may also explicate how superdeep diamonds land in a station where a kimberlite can catch them .
" Deep diamond can inform us more about subduction process , mantle convection , liquid - stone interactions and other processes happening below the crust during supercontinent cycles , " Timmerman said .
There are many other question to answer , she added . For instance , scientists still do n’t know how subducted plates change the floor of supercontinents and whether that affects how long a supercontinent lasts before breaking up . Another open interrogative sentence is whether this reuse crustal material influence when and where kimberlite magmas form .
Ancient rhombus may also tell us about other milepost in Earth ’s chaotic history .
— rarefied diamonds suggest piss bushwhack deeply in Earth ’s interior than scientist believe
— gargantuan blobs in Earth ’s pallium may be driving a ' diamond factory ' near our major planet ’s core
— Strange , never - before - regard diamond crystal structure found inside ' Diablo Canyon ' meteorite
Some infield are forged from C that was comprise into Earth upon its formation , Olierook said , while others make from carbon from ancient life , dragged down along with slabs of subducted crust . It ’s potential to narrate which summons formed the diamonds by analyzing the molecular structure of the C within diamond inclusions . These inclusion can thus hold closed book about brumous number in Earth history , such as when widespread subduction began or when life in the oceans became prevalent .
But to get at those answers , researcher will need to get better at estimate out how old diamonds are . And they ’ll need more diamonds that are both ancient and from the deep depths .
" Going back in metre from the most recent supercontinent detachment to the unity before that , " Olierook said , " I strongly suspect there are still muckle to be find . "
