In the southwest Indian Ocean , the volcanic island of Anjouan is home to a unknown geological mystery . On the island , residents and geologists keep finding a character of rock that should n’t be there .
The island formed on an ocean basin , whentectonic platesshifted away from each other and magma moved up and cool down to form basalt , of which the island is made . On Anjouan you should not expect to find the aqueous rock quartzite , a type of sandstone made from quartz Baroness Dudevant grain that have been collected in river deltas , before being compact into quartzite over metre . The island’sbasaltdoes not contain any quartz , and the island itself istoo youngto have formed a sizeable river delta . And yet , on the island geologists have reported for perhaps over a century that they have found quartzite in teemingness .
In 1900 geologists reported strange rocks that could have been quartzite , though the documentation was too miserable to know for sure . In 1969 , geologist found a orotund formation of " sandstone " on the island near the town of Tsembehou , which was later found to be quartzite . Then in 2017 , French geologist Patrique Bachèlery found more quartzite at a nearby ridgepole . Setting out a few years later , geochemist at Columbia University ’s Lamont - Doherty Earth Observatory Cornelia Class started to look into . Sure enough , she and her squad found quartzite within instant , and an teemingness of it up along the ridge .
“ This is perverse to dental plate plate tectonics , ” Class said in aColumbia Universitypress release . “ Quartzite bodies do not belong on volcanic islands . ”
Residents order Class that they find the rock candy all the time , and use it to sharpen their knife , point them in the way of yet more quartzite . Mapping it out , Class found that the amount of quartzite was " almost half a muckle " .
As yet , there is n’t a definitive explanation for the quartzite . A clump of quartzite from continental impudence must have found itself wedge in the sea lavatory , and then raise up 4,000 meter ( 13,120 feet ) above the seabed by the pyrogenous basalt , yet Class toldLive Sciencethat the interpersonal chemistry of the island ’s basalt tilt do n’t show an association with continental insolence , ring the uncovering " something we study unsufferable , but then we find it , and once we find it , we have to explain it . "
get on the quartzite will assist define when it was deposited , and hopefully how it came to be the only volcanic island in the world with a clump of continent – perchance from the separation of ancient continentGondwana – sit on it .
