Since it was 'lighter' than both the mantle and the ocean floor, these silica-rich rocks were not subducted and remained floating on the surface, eventually getting thick enough to rise above the water level as islands.
Kusukela yaba 'lula' kunayo yomibili imantle kanye nesiyilo selwandle, lawa matje e silica-lenemsoco bekaphusheki kuya phansi kepha bekandanda ngetulu, ekugcineni ngekuba nesisindvo lesenele kukhuphukela ngetulu kwemanti njenge tichingi.