The best evidence for the layered-mantle thesis is the well-established fact that volcanic rocks found on oceanic islands，islands believed to result from mantle plumes arising from the lower mantle，are composed of material fundamentally different from that of the mid-ocean ridge system， whose source，most geologists contend，is the upper mantle.
對于地幔分層論點(diǎn)來說，的證據(jù)乃這樣一個確認(rèn)的事實(shí)，即在那些海洋島嶼——這些島嶼據(jù)信是源于由下層地幔升上來的地幔柱狀溶巖流(mantle plume)——上發(fā)現(xiàn)的火山巖石，是由與海洋中部山脊系統(tǒng)的物質(zhì)根本不同的物質(zhì)構(gòu)成的，而這一海洋中部山脊系統(tǒng)的成因，大多數(shù)地質(zhì)學(xué)家論辯道，為上部地幔。