万物简史 第298期:地下的烈火(6)

He had discovered the boundary between the crust and the layer immediately below, the mantle; 他发现地壳与下面一层即地幔的界线， this zone has been known ever since as the Mohorovicic discontinuity, or Moho for short. 此后，这个区

万物简史 第299期:地下的烈火(7)

The scale is of course more an idea than an object, an arbitrary measure of the Earth's tremblings based on surface measurements. 当然，里氏震级是一个概念，不是一件东西，是一个根据地面测量的结果武断地得出的地球震

万物简史 第300期:地下的烈火(8)

As you will gather from this, measuring earthquakes is not always an exact science, particularly when interpreting readings from remote locations. 你从中可以知道，测量地震并不总是一门很精确的科学，尤其在牵涉到解释来自

万物简史 第301期:地下的烈火(9)

The San Francisco earthquake of 1906, for comparison, measured an estimated 7.8 on the Richter scale and lasted less than thirty seconds. 相比之下，1906年的旧金山地震只有里氏7.8级，持续了不到30秒。 Earthquakes are fairly comm

万物简史 第302期:地下的烈火(10)

Tokyo stands on the boundary of three tectonic plates in a country already well known for its seismic instability. 日本已经是个以多地震闻名的国家，而东京恰好又位于三个构造板块的相遇之处。 In 1995, as you will remem

万物简史 第303期:地下的烈火(11)

The most notorious such quakes ever to hit the United States were a series of three in New Madrid, Missouri, in the winter of 1811-12. 在美国经历过的这类地震当中，最著名的要算是1811-1812年冬发生在密苏里州新马德里的一

万物简史 第305期:地下的烈火(13)

Four years later, Soviet scientists decided to try their luck on dry land. 4年以后，苏联科学家决定在陆地上碰碰运气。 They chose a spot on Russia's Kola Peninsula, near the Finnish border, and set to work with the hope of drilling

万物简史 第306期:地下的烈火(14)

Because we can't see into the Earth, we have to use other techniques, which mostly involve reading waves as they travel through the interior. 我们无法看到地球的深处，因此不得不使用别的方法，主要包括观察波在地球内部的

万物简史 第307期:地下的烈火(15)

So how much do we know about what's inside the Earth? Very little. 因此说，我们对地球的内部情况究竟了解多少？很少。 Scientists are generally agreed that the world beneath us is composed of four layers, 科学家们普遍认为，

万物简史 第308期:地下的烈火(16)

How and when the Earth got its crust are questions that divide geologists into two broad camps, 地球如何有了地壳，何时有了地壳，这两个问题把地质学家分成两大阵营， those who think it happened abruptly early in the Eart

万物简史 第309期:地下的烈火(17)

The hour hand on a clock moves about ten thousand times faster than the flowing rocks of the mantle. 钟面上时针的移动速度，比地幔岩石的流动速度，要快大约1万倍。 The movements occur not just laterally as the Earth's plates

万物简史 第310期:地下的烈火(18)

So all that can be said is that at some slightly indeterminate point as we head toward the center of Earth we leave the asthenosphere and plunge into pure mantle. 因此，我们只能说，在前往地球中心的过程中，我们会在某个不大确

万物简史 第311期:地下的烈火(19)

The outer core is in many ways even less well understood, though everyone is in agreement that it is fluid and that it is the seat of magnetism. 外核在许多方面被了解得更少，虽然大家都认为它是液态的，是产生磁力的地方。

万物简史 第312期:地下的烈火(20)

We may be going through a reversal now. 我们现在也许正经历一次逆转。 The Earth's magnetic field has diminished by perhaps as much as 6 percent in the last century alone. 仅仅在过去的一个世纪里，地球的磁场就减弱了大约

万物简史 第313期:地下的烈火(21)

At that time, the lower forty-eight United States had not seen a volcanic eruption for over sixty-five years. 当时，美国本土的48个州在过去的65年里没有见过火山爆发。 Therefore the government volcanologists called in to monitor

万物简史 第314期:地下的烈火(22)

Almost the only person who believed that something really bad might happen was Jack Hyde, a geology professor at a community college in Tacoma. 几乎只有一个人认为真的快出大问题了，他就是塔科马一所社区学院的地质学教授

万物简史 第315期:地下的烈火(23)

The luckiest person on that day was a graduate student named Harry Glicken. 那一天最走运的要算是一位名叫哈里格利肯的研究生。 He had been manning an observation post 5.7 miles from the mountain, 他是离火山9公里处一个观

万物简史 第316期:地下的烈火(24)

In an extraordinarily unself-critical book called Surviving Galeras, Williams said he could only shake my head in wonder when he learned afterward 但威廉斯毫不自责，在一本名叫《加莱拉斯火山幸存记》的书里说，当他后来听

万物简史 第317期:地下的烈火(25)

Ninety minutes after the blast, ash began to rain down on Yakima, Washington, 爆发90分钟以后，灰烬开始雨滴般地洒落在华盛顿州的亚基马。 a community of fifty thousand people about eighty miles away. 那是个有5万人口的社

万物简史 第304期:地下的烈火(12)

And what causes these massive intraplate rupturings? 这种跨板块大地震是怎么发生的？ Something deep within the Earth. 原因在地球深处。 More than that we don't know. 更多的情况我们就不知道了。 By the 1960s scientists