英语每日一听 | 每天少于5分钟

第1790期:The continents are moving. When will they collide?


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In the early 20th century, a meteorologist named Alfred Wegener noticed striking similarities between the coasts of Africa and South America. These observations led him to propose a controversial new theory: perhaps these and many other continents had once been connected in a single, gigantic landmass. Wegener’s Theory of Continental Drift directly contradicted the popular opinion that Earth’s continents had remained steady for millennia, and it took almost 50 years for his advocates to convince the larger scientific community. But today, we know something even more exciting— Pangea was only the latest in a long lineage of supercontinents, and it won’t be the last.

20 世纪初,一位名叫阿尔弗雷德·韦格纳 (Alfred Wegener) 的气象学家注意到非洲和南美洲海岸之间惊人的相似之处。这些观察使他提出了一个有争议的新理论:也许这些大陆和许多其他大陆曾经连接在一个巨大的大陆上。韦格纳的大陆漂移理论直接与地球大陆几千年来保持稳定的流行观点相矛盾,他的支持者花了将近 50 年的时间才说服更大的科学界。但是今天,我们知道了一些更令人兴奋的事情——盘古大陆只是一长串超级大陆中最新的一个,而且不会是最后一个。


Continental Drift laid the foundation for our modern theory of plate tectonics, which states that Earth’s crust is made of vast, jagged plates that shift over a layer of partially molten rock called the mantle. These plates only move at rates of around 2.5 to 10 centimeters per year, but those incremental movements shape the planet's surface. So to determine when a new supercontinent will emerge, we need to predict where these plates are headed.

大陆漂移为我们的现代板块构造理论奠定了基础,该理论指出地壳由巨大的锯齿状板块组成,这些板块在称为地幔的部分熔融岩石层上方移动。这些板块每年仅以约 2.5 至 10 厘米的速度移动,但这些增量运动塑造了地球表面。因此,要确定新的超大陆何时出现,我们需要预测这些板块的走向。


One approach here is to look at how they’ve moved in the past. Geologists can trace the position of continents over time by measuring changes in Earth’s magnetic field. When molten rock cools, its magnetic minerals are “frozen” at a specific point in time. So by calculating the direction and intensity of a given rock’s magnetic field, we can discover the latitude at which it was located at the time of cooling. But this approach has serious limitations. For one thing, a rock’s magnetic field doesn’t tell us the plate’s longitude, and the latitude measurement could be either north or south. Worse still, this magnetic data gets erased when the rock is reheated, like during continental collisions or volcanic activity. So geologists need to employ other methods to reconstruct the continents’ positions. Dating local fossils and comparing them to the global fossil record can help identifying previously connected regions. The same is true of cracks and other deformations in the Earth's crust, which can sometimes be traced across plates.

这里的一种方法是查看它们过去的移动方式。地质学家可以通过测量地球磁场的变化来追踪大陆随时间的位置。当熔岩冷却时,其磁性矿物会在特定时间点“冻结”。因此,通过计算给定岩石磁场的方向和强度,我们可以发现它在冷却时所处的纬度。但这种方法有严重的局限性。一方面,岩石的磁场并不能告诉我们板块的经度,纬度测量值可能是北也可能是南。更糟糕的是,当岩石被重新加热时,这些磁性数据会被删除,比如在大陆碰撞或火山活动期间。因此,地质学家需要采用其他方法来重建大陆的位置。确定当地化石的年代并将它们与全球化石记录进行比较可以帮助识别以前连接的区域。地壳中的裂缝和其他变形也是如此,有时可以跨越板块追踪。


Using these tools, scientists have pieced together a relatively reliable history of plate movements, and their research revealed a pattern spanning hundreds of millions of years. What’s now known as the Wilson Cycle predicts how continents diverge and reassemble. And it currently predicts the next supercontinent will form 50 to 250 million years from now. We don’t have much certainty on what that landmass will look like. It could be a new Pangea that emerges from the closing of the Atlantic. Or it might result from the formation of a new Pan-Asian ocean. But while its shape and size remain a mystery, we do know these changes will impact much more than our national borders.

使用这些工具,科学家们拼凑出了相对可靠的板块运动历史,他们的研究揭示了一种跨越数亿年的模式。现在被称为威尔逊循环的东西预测了大陆是如何分开和重新组合的。它目前预测下一个超级大陆将在 50 到 2.5 亿年后形成。我们不太确定那块大陆会是什么样子。它可能是大西洋关闭后出现的新盘古大陆。或者它可能是新泛亚洋形成的结果。但是,尽管它的形状和大小仍然是个谜,但我们知道这些变化的影响将远远超过我们的国界。


In the past, colliding plates have caused major environmental upheavals. When the Rodinia supercontinent broke up circa 750 million years ago, it left large landmasses vulnerable to weathering. This newly exposed rock absorbed more carbon dioxide from rainfall, eventually removing so much atmospheric CO2 that the planet was plunged into a period called Snowball Earth. Over time, volcanic activity released enough CO2 to melt this ice, but that process took another 4 to 6 million years. Meanwhile, when the next supercontinent assembles, it's more likely to heat things up. Shifting plates and continental collisions could create and enlarge cracks in the Earth’s crust, potentially releasing huge amounts of carbon and methane into the atmosphere. This influx of greenhouse gases would rapidly heat the planet, possibly triggering a mass extinction. The sheer scale of these cracks would make them almost impossible to plug, and even if we could, the resulting pressure would just create new ruptures.

过去,板块碰撞曾造成重大的环境剧变。大约 7.5 亿年前,当罗迪尼亚超级大陆分裂时,大片大陆容易受到风化作用的影响。这块新暴露的岩石从降雨中吸收了更多的二氧化碳,最终去除了如此多的大气中的二氧化碳,以至于地球陷入了一个被称为雪球地球的时期。随着时间的推移,火山活动释放出足够的二氧化碳来融化这些冰,但这个过程又需要 4 到 600 万年。同时,当下一个超级大陆聚集时,它更有可能使事情升温。移动的板块和大陆碰撞可能会在地壳中产生和扩大裂缝,可能会向大气中释放大量的碳和甲烷。温室气体的涌入将迅速加热地球,可能引发大规模灭绝。这些裂缝的巨大规模使它们几乎不可能被堵塞,即使我们可以,由此产生的压力只会造成新的破裂。


Fortunately, we have at least 50 million years to come up with a solution here, and we might already be onto something. In Iceland, recently conducted trials were able to store carbon in basalt, rapidly transforming these gases into stone. So it’s possible a global network of pipes could redirect vented gases into basalt outcrops, mitigating some of our emissions now and protecting our supercontinental future.

幸运的是,我们至少有 5000 万年的时间来找到解决方案,而且我们可能已经有所作为。在冰岛,最近进行的试验能够将碳储存在玄武岩中,迅速将这些气体转化为石头。因此,全球管道网络有可能将排出的气体重新定向到玄武岩露头,从而减少我们现在的一些排放并保护我们超大陆的未来。



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英语每日一听 | 每天少于5分钟By 晨听英语

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