分析GRE阅读中的难句难词_GRE阅读

分析GRE阅读中的难句难词

　　现在，我们拿GRE阅读NO题的NO8-1这篇文章做一个示范，来说明一下怎样提高新GRE阅读能力。

　　NO8-1，我们从词--句--篇章来谈谈这篇文章。

　　原文：

　　Geologists have long known that the Earths mantle is heterogeneous， but its spatial arrangement remains unresolvedis the mantle essentially layered or irregularly heterogeneous? 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.Some geologists， however， on the basis of observations concerning mantle xenoliths， argue that the mantle is not layered， but that heterogeneity is created by fluids rich in incompatible elements percolating upward and transforming portions of the upper mantle irregularly， accordingto the vagaries of the fluids pathways. We believe， perhaps unimaginatively， that this debate can be resolved through further study， and that the underexplored midocean ridge system is the key.