考满分 toefl

1 .Listen to part of a lecture in a geology class.

听一段地质学课上的讲座片段。

1 .P: All right. Last class, we talked about the ocean floor, what it looks like and how it was formed. We discussed underwater plateaus, large flat regions that rise above the level of the sea floor, and underwater volcanoes. It's been hard for us to learn much about these structures because they're so far underwater, usually several kilometers below the ocean's surface.

教授：好的。上节课我们讨论了洋底是什么样子以及它是如何形成的。我们谈到了海底高原--也就是高于海底平面的大型平坦区域，以及海底火山。由于这些结构通常位于海下数公里的深处，我们对它们的了解一直非常有限。

1 .But there's one formation in particular that's shedding new light on these structures. It's called Tamu Massif. Tamu Massif is a structure that's part of a huge plateau in the Pacific Ocean, about 1000 kilometers east of Japan. We've known about Tamu Massif for quite a while, since the early 20th century. We assumed for most of that time that Tamu Massif was formed by output from many volcanoes. This is pretty common on Earth. Several different volcanoes erupt, and their output eventually merges them into one large structure. Take the islands of Hawaii, for instance. We know they were formed by volcanic activity, right? And the largest of Hawaii's islands, also called Hawaii, was formed by output from five volcanoes. So it was easy for us to assume that something similar was true of Tamu Massif.

不过有一个特殊构造为我们提供了新的认知，它叫做大塔穆火山（Tamu Massif）。大塔穆火山是太平洋中一个巨大高原的组成部分，位于日本以东约1000公里处。自20世纪初以来，我们就知道大塔穆火山的存在。长期以来，我们假设它是由多个火山喷发出的产物形成的。这在地球上很常见。多个不同的火山喷发，喷发的产物融合形成了一个巨大的构造。 例如，我们都知道夏威夷群岛就是火山活动形成的，对吧？其中最大的夏威夷岛，一样也称为夏威夷，是由五座火山的喷发物共同构成。因此我们自然认为大塔穆火山也遵循类似的形成模式。

1 .But researchers recently took several rock samples from the structure, samples of hardened lava, and discovered that all the samples they took have a similar chemical composition. The chemical composition of lava comes in part from the volcanic vent it travels through. So this similarity in the samples suggests that Tamu Massif is actually one large volcano with a single vent. If this evidence holds up, it would mean that Tamu Massif is the largest single volcano on Earth, not necessarily in terms of its height, but of its area, the amount of space it covers. As you can imagine, this raises a lot of questions. For one thing, how did Tamu Massif form? It appears that the sea floor might have had just the right circumstances for the formation of a massive volcano. First of all, Earth's crust was thin and fragile in this spot, and also, Tamu Massif formed at the juncture of three plates in Earth's crust. Because of these weaknesses in the crust, it would have been easy for magma below to push its way out, would have just poured out in massive quantities.

但最近研究者从其不同位置采集了多个硬化的熔岩样本，发现所有样本都具有相似的化学成分。由于熔岩的化学成分部分是来自其流经的火山口，这种相似性表明大塔穆火山实际上也是一个拥有单一火山口的巨大火山。 如果证据成立，这将意味着大塔穆火山，虽然高度未必是最高的，但它将成为地球上覆盖面积最大的单体火山。正如你们可以想象到的，这引发了许多问题。首先，大塔穆火山是如何形成的呢？似乎该区域的海底正好就拥有形成巨大火山的条件。首先，该区域的海底地壳薄而脆弱，且位于三个地壳板块交界处。因为这样的地质条件，下方岩浆更容易持续的大规模喷发。

1 .And it's not just the size that's interesting, but also the shape. You see, Tamu Massif has these incredibly low slopes and covers a huge area. So what probably happened was, there were several large eruptions from the center of the volcano that took place over a relatively short period of time. The quantity of magma released was so great it would have spread out really far, cooling gradually, and that's how we get these surprisingly shallow slopes. Now, our current models of volcano formation are based on volcanoes much smaller than this one. We simply didn't know until now that volcanoes of Tamu Massif's size could exist on Earth. We'll need new models to account for volcanoes of this size.

不只是它的大小，其形状也很有趣。如你所见，大塔穆火山具有极缓的坡度，却能覆盖广阔的区域。可能的情况是：短时间内存在多次从火山中心大规模的喷发。巨量的岩浆快速扩散并逐渐冷却，从而形成这种独特的缓坡地貌。目前我们的火山形成模型都基于比它小得多的火山。我们直到现在才知道，地球可能存在如此规模的火山，我们需要建立新的模型来解释这种巨型火山。

1 .So like, what about other volcanoes in our solar system? I read somewhere that the biggest volcano is Olympus Mons on Mars.

学生：那太阳系里其他的火山呢？我记得哪里说到过，最大的是火星的奥林帕斯山。

1 .Olympus Mons is, as far as we know, the biggest volcano in our solar system. But while Tamu Massif is shorter than Olympus Mons, it covers approximately the same area. Like I said, this isn't something that we would have guessed. Then again, we actually know more about some volcanoes in outer space than we do about volcanoes on the ocean floor.

奥林帕斯山就目前我们所了解的，确实被认为是太阳系最大的火山。虽然大塔穆火山的高度不及奥林帕斯山，但其覆盖面积与它大致相当。如我所说，这不是我们会猜到的事情。再说了，我们实际上对外太空的一些火山了解得比对海底火山要多。

1 .So that misunderstanding might just have been because many of our volcanoes have found a good place to hide under the sea, where darkness and pressure from the water make it difficult for us to explore. On the other hand, we have many clear and useful images of the surface of Mars. It's exciting to realize that we still have so much more to discover about our own planet.

所以这种误解可能是因为我们的许多火山找到了一个藏在海底的好地方，那里的黑暗和水压的环境使探测异常困难。另外，我们有了很多关于火星表面的清晰影像。令人振奋的是，这提醒我们地球仍有许多待发现之谜。

1 .So what are the next steps? Perhaps we should start looking for more of these volcanoes, but I don't necessarily think that's our most important goal at the moment. We still need to understand more about how such a huge quantity of magma could spill out from a single point of origin. Learning more about this phenomenon will give us better insight into how underwater structures form.

接下来该怎么做呢？也许我们应该开始寻找更多这样的火山，但我不一定认为这是我们目前最重要的目标。我们仍然需要更多地了解如此大量的岩浆如何能从一个单一的喷发点涌出。深入研究这种现象将帮助我们更好理解海底结构是如何形成的。