以下是引用anchoret在2003-4-21 2:56:00的发言: Many geologists theorize that the trail of volcanic craters and cinder cones along the Snake River plain of southern Idaho was produced as the North American continent slid westward over a stationary “plume”, a vertical channel through which molten rock rose intermittently from the Earth’s core to burst through its curst.
Which of the following, if true, tends to support the geologists’ theory of how the trail was produced?
(A) The largest craters and cinder cones are on the eastern margin of the trail. (B) The most violent volcanic activity apparently occurred at the western margin of the trail. (C) The craters and cinder cones are evenly spaced throughout the extent of the trail. (D) The newest craters and cinder cones are on the eastern margin of the trail. (E) The craters and cinder cones on the western margin of the trail generally took longer to form than did those on the eastern margin.
我先不写答案,没作过这道题的xdjm可以测试一下自己的判断(2min limit) 请作过这道题的xdjm也不要急着公布答案,可以尝试以下讨论其逻辑结构。
结论:沿着某条河流的火山锥群是大陆西向飘逸的时候形成的。
事实:大陆漂移经过了一个垂直的,冲破地壳的火山熔岩出口。
寻求结论的支持项。
a,最大的火山锥群在飘逸痕迹的东面。(局部,片面)
b,最猛烈的火山活动是在飘逸痕迹的西面。(同上)
c,火山锥群均匀的分布在飘逸痕迹的范围内。(反对)
d,新形成的火山锥群在飘逸痕迹的东面。
e,西边的火山锥群要比东面的花费多时间形成。(无关) |