标题: No8-1 AS Q19:TYPICAL? [打印本页] 作者: HardyNibor 时间: 2013-9-27 21:26:58 标题: No8-1 AS Q19:TYPICAL?
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 midocean ridge system, whose source, most geologists contend, is the upper mantle.
We believe, perhaps unimaginatively, that this debate can be resolved through further study, and that the underexplored midocean ridge system is the key.
19. It can be inferred from the passage that the supporters of the “layered-mantle” theory believe which of the following?
II. The materials of which volcanic rocks on oceanic islands and midocean ridges are composed are typical of the layers from which they are thought to originate.