In the southwestern Indian Ocean , the volcanic island of Anjouan is home to a strange geologic 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 basinful , whentectonic platesshifted forth from each other and magma moved up and cooled to form basalt , of which the island is made . On Anjouan you should not expect to find the sedimentary rock ‘n’ roll quartzite , a type ofsandstonemade from quartz sand grains that have been pull in in river delta , before being contract into quartzite over time . The island’sbasaltdoes not contain any quartz , and the island itself is too young to have formed a sizeable river delta .
And yet , on the island geologists have reported for perhaps over a hundred that they have found quartzite in teemingness .
In 1900 geologists report unusualrocksthat could have been quartzite , though the documentation was too piteous to cognize for sure . In 1969 , geologists found a enceinte formation of " sandstone " on the island near the town of Tsembehou , which was by and by found to be quartzite . Then in 2017 , French geologist Patrique Bachèlery found more quartzite at a nearby ridge .
set out a few years later , geochemist at Columbia University ’s Lamont - Doherty Earth Observatory Cornelia Class bulge to investigate . for certain enough , she and her squad find oneself quartzite within minutes , and an abundance of it up along the ridge .
“ This is contrary to plate tectonics , ” Class tell in aColumbia Universitypress release . “ Quartzite bodies do not belong to on volcanic islands . ”
resident physician told Class that they see the rocks all the metre , and use it to focus their knives , aim them in the direction of yet morequartzite . mathematical function it out , Class get hold that the amount of quartzite was " almost half a mickle " .
As yet , there is n’t a authoritative account for the quartzite . A chunk of quartzite from continental crust must have found itself deposited in the ocean washbowl , and then raised up 4,000 measure ( 13,123 feet ) above the seabed by the eruptive basalt , yet Class toldLive Sciencethat the alchemy of the island ’s basalt rocks do n’t show an tie with continental impudence , holler the find " something we see impossible , but then we rule it , and once we find it , we have to explain it . "
Aging the quartzite will facilitate find out when it was posit , and hopefully how it come to be the only volcanic island in the humankind with a ball of continent – perhaps from the breakup of ancient continentGondwana – sit on it .
An earlier adaptation of this article was first issue inMay 2023 .
