Narrator: Listen to part of a lecture in a geology class.

旁白：听一段地质学的演讲。

Professor: As we've discussed, Earth's crust is made up of large plates that rest on a mantle of molten rock.

教授：就像我们所讨论的，地壳是由依靠在由熔岩组成的地幔上的大板块组成。

These plates…uh…now these tectonic plates support the continents and oceans.

这些板块……额……这些构造板块支撑着大陆和海洋。

Over time, the tectonic plates move and shift, which moves the continents and the ocean floors too.

随着时间流逝，这些构造板块发生移动，这个也使得大陆洲和洋底发生移动。

Once it was understood how these plates move, it was possible to determine past movements of Earth's continents and how these slow movements have reshaped Earth's features at different times.

一旦了解了这些板块是怎么移动的，就有可能知道地球大陆洲在过去是怎么移动的，以及这样的缓慢移动是怎么在不同时期改造地球特征的。

OK. Well, (as) studying the movements of the plates can tell us about the location of the continents in the past, it can conceivably tell us about their location in the future too, right?

好的，既然研究板块移动可以告诉我们大陆洲在过去的位置，它也可以很确切地告诉我们这些洲未来的位置，不是吗？

So, in recent years, some geologists have used plate tectonic theory to make what they call geopredictions.

因此，在最近几年，一些地质学家已经使用板块构造学说来做他们所谓的地理预测。

Geopredictions are guesses about what Earth's surface might look like millions of years from now.

地理预测是指预测在未来上百万年中，地球表面可能会变成什么样子。

So, we know how certain continents are currently moving.

我们知道某些大陆洲现在是怎么移动的。

For example, the continents of Africa has been creeping north toward Europe and Australia has been making its way north too, toward Asia.

比如，非洲大陆在向北边的欧洲慢慢移动。而澳洲也在向北边的亚洲慢慢靠近。

Does anyone know what's happening to the Americas?

有人知道美洲怎么样了吗？

I…I think we've talked about that before. Lisa?

我觉得我们之前讨论过这个，Lisa?

Student: They are moving westward, away from Europe and Africa. Right?

学生：他们正在向西移动，远离欧洲和非洲，对吗？

Professor: Right. And what makes us think that?

教授：正确。那又是什么让我们有这个想法的呢？

Student: The Atlantic Ocean floor is spreading and getting wider, so there is more ocean between the Americas and Europe and Africa.

学生：大西洋海底逐渐扩张，变得越来越宽；所以在美洲、欧洲和非洲之间会有更多的海洋。

Professor: OK. And why is it spreading?

教授：好的。那为什么它在延伸呢？

Student: Well, the seafloor is split.

学生：嗯，海底有一个裂缝。

There is a ridge, a mountain range that runs north and south there.

有一个贯穿南北的山脊。

And the rock material flows up from Earth's interior here, at the split, which forces the two sides of the ocean floor to spread apart, to make room for the new rock material.

在分裂处岩石物质流从地球内部流出，使海底向两侧分开，为岩石物质提供了空间。

Professor: Good. And that means, over the short term…uh… and by short term I mean 50 million years, that's a blink of the eye in geological time.

教授：很好。这就意味着，在短期之内，我说的短期是5000万年，在地质时间上只是眨眼的一瞬间。

Um…over the short term, we can predict that the Americas will continue to move westward, farther away from Europe, while Africa and Australia will continue to move northward.

额…在短期上来说，我们可以预测美洲会继续向西移动，远离欧洲，而非洲和澳洲也会继续向北移动。

But what about over the long term?

但是，从长期上来看会怎么样？

Say 250 million years or more.

比如2亿5千万年或者更长。

Well, over that length of time, forecasts become more uncertain.

超过这种时间跨度，预测就变得不是那么肯定了。

But lots of geologists predict that eventually all the continents, including Antarctica, will merge and become one giant land mass, a super continent, one researchers calling Pangaea Ultima, which more or less means the last super continent.

但是，很多地质学家预测，所有的大陆，包括南极洲，最终会合并起来变成一个巨大的大陆块，一个超级大陆，研究人员称之为盘古大陆。这或多或少意味着最后一个超级大陆。

Now, how that might happen is open to some debate.

现在，那个是怎么发生的还是有争议的。

Some geologists believe that the Americas will continue to move westward and eventually merge with East Asia.

一些地质学家认为美洲还是会继续向西移动，然后最终和东亚合并。

This hypothesis is based on the direction the Americas are moving in now.

这个假设是基于美洲现在移动的方向建立的。

But others hypothesize that a new super continent will form in a different way.

但是其他一些地质学家认为超级大陆会用不同的方法形成。

They think that a new subduction zone will might occur at the western edge of the Atlantic Ocean.

他们认为一个新的俯冲带会在大西洋西岸形成。

Paul, can you remind us what a subduction zone is?

Paul,你能提醒我们一下什么是俯冲带吗？

Student: Yeah. Um…basically, a subduction zone is where two tectonic plates collide.

学生：好的。基本上来说，一个俯冲带就是两个构造板块相撞的地方。

So if an ocean floor tectonic plate meets the edge of a continent and they push against each other, the heavier one sinks down and goes under the other one.

所以，如果一个大洋底板块和一个陆地板块的边相碰，并且他们互相推挤另一方，重的那个就会沉下去，沉到轻的那个的下面。

So the…um…the oceanic plate is made of denser and heavier rock, so it begins to sink down under the continental plate and into the mantle.

所以，额，大洋板块就由越来越密、越来越厚重的岩石组成，然后它就开始沉到大陆板块的下方，并且进入到地幔中去。

Professor: Right. So the ocean floor would kind of slide under the edge of the continent.

教授：正确。所以大洋底会滑到大陆边缘的下方。

And once the ocean plate begins to sink, it would be affected by another force--slab pull.

而且，一旦大洋板块开始下沉，它也会受到另一个力量的影响——平板的拉力。

Slab pull happens at the subduction zone.

平板拉力发生在俯冲带。

So to continue our example…As the ocean floor plate begins to sink down into the mantle, it would drag or pull the entire plate along with it.

继续我们的例子，当大洋底板块开始沉到地幔，它会拖拽整个板块和它一起下沉。

So more and more of this plate, the ocean floor, would go down under the continent into the mantle. OK?

这么一来，越来越多的板块，大洋底，会沉到大陆板块下面，到达地幔。明白吗？

So, as I said, currently the Atlantic Ocean floor is spreading, getting wider, but some researchers speculate that eventually a subduction zone will occur where the oceanic plate meets the continental plate of the Americas.

就像我说的，现在大西洋底正在扩张，变得越来越宽，但是一些研究人员推测最终一个俯冲带会在美洲的大洋板块和大陆板块交汇处出现。

If that happens, slab pull could draw the oceanic crust under the continent, actually causing the Americas to move eastward toward Europe and the ocean floor to get smaller.

如果那个发生了，平板拉力会将海洋地壳拖到大陆板块下面，事实上，使得美洲向东朝着欧洲移动，并且大洋底会变得更小。

That is, the Atlantic Ocean would start to close up, narrowing the distance between the eastern edge of the Americas and Europe and Africa.

也就是说，大西洋会开始闭合，缩短了美国东边和欧洲、非洲之间的距离。

So they form a single super continent.  

因此，他们形成了一个超级大陆。