火山喷发是Burp还是爆炸?

温馨提示:全文约9952字,阅读全文大约需要10分钟

去年12月,熔岩的膨胀液开始挤出LaSoufrière的峰会,该火山在圣文森特的加勒比海岛上的火山。然后在3月下旬和4月初,火山开始发出与迅速上升的岩浆相关的地震波。有毒的烟雾从峰值剧烈排出。

害怕魔法炸弹迫在眉睫,科学家们觉得令人惊叹了,政府于4月8日撤回了岛屿的北部。第二天,火山开始灾难性地爆炸。

火山科学家已经越来越详细了解可能产生爆发性爆发的条件。相比之下,Gloopier岩浆施加强大的力量,推动开放的途径。

去年12月,熔岩的膨胀液开始挤出LaSoufrière的峰会,该火山在圣文森特的加勒比海岛上的火山。效果起初慢;没有人受到威胁。然后在3月下旬和4月初,火山开始发出与迅速上升的岩浆相关的地震波。有毒的烟雾从峰值剧烈排出。

害怕魔法炸弹迫在眉睫,科学家们觉得令人惊叹了,政府于4月8日撤回了岛屿的北部。第二天,火山开始灾难性地爆炸。疏散刚刚及时来:在撰写本文时,没有生命已经丢失了。

同时,在北极边缘发生了一定的超级相似但深刻不同。

自2019年末以来,冰岛雷克朗斯半岛的越来越强烈的构造地震在冰岛的雷克朗斯半岛下面隆隆声,强烈意味着黑社会正在开放,为岩浆制造空间。 2021年初,作为岩浆围绕半岛迁移的地下蛇,寻找逃生舱口到表面,地面本身开始改变形状。然后在3月中旬,几个裂缝的裂缝大致蜿蜒穿过地球,在科学家们期望它可能,将熔岩洒到一个名为Geldingadalur的无人居住的山谷。

在这里,当地人立即植入喷发,野餐和摆在自拍照的掠过者的掠过者远离熔岩流。一场音乐会最近发生在那里,人们用圆形剧场的座位对待山脊。

在这两种情况下,科学家们不仅仅准确地表明新的爆发正在进行中。他们还预测了这两种非常不同的形式,这些爆发会采取。虽然“当”当“部分方程”的一部分永远不容易预测,但“如何”部分恰当是尤其具有挑战性,特别是在LaSoufrière爆炸性爆发的情况下。 “这是一个棘手的人,他们钉了它,他们绝对钉了它,”卡内基科学机构的火山学家Diana Roman说。

火山科学家已经越来越详细了解可能产生爆发性爆发的条件。例如,岩浆本身的气氛和覆盖性的地下水的存在或不存在。在最近的一系列研究中,研究人员已经展示了如何读取隐藏的信号 - 从地震波到卫星观测 - 因此他们可以更好地预测喷发将如何发展:爆炸或呜咽。

与摩天大楼或大教堂一样,地球火山的建筑设计繁荣不同。您可以获得高大陡峭的火山,超膨胀和浅倾斜的火山,以及巨大的宽敞的火山岩。有时没有火山,但小凹陷的链或裂缝的群疤痕像爪子标记一样。

爆发预测问了很多问题。他们中间的职务是:什么时候?在其核心,这个问题相当于询问下面的岩浆将通过导管(岩浆和表面开口之间的管道之间的管道一起行驶,并作为熔岩流量和灰烬,作为火山玻璃和炸弹。

当岩浆从深度上升时,它可以改变火山的建筑,从字面上改变了上面的土地的形状。迁移岩浆流动还可以强制摇滚,产生火山构造地震。当压力保持岩浆陷阱地下下降时,它释放出陷阱气体,可以逸出到表面。

爆发预报员寻找其中的任何三个迹象:火山的形状,其地震音景观或其放气的变化。如果你在从火山的日常行为明显截然不同的所有三种变化中间谍变化 - 那么“毫无疑问会发生一些事情,”意大利佛罗伦萨大学的地球物理主义者Maurizio Rapepe说。事情往往是,最终是一种爆发。

变化并不总是意味着活动中的上升。大多数火山在爆发之前都会变得嘈杂,但有时相反。例如,冰岛的地震论家在开启Reykjanes的前五个裂缝之前立即在火山震颤中录制了一滴。当冰岛地球节的地震学家都说ThorbjörgÁgústsdótir说,科学家们预测,第六裂,即将出现第六个裂缝 - 他们是对的。

越来越多,不仅可以预测火山会爆发,而且是如何爆发的。

如果单个火山往往有自己的爆发风格,则不起每个特定火山的历史是关键的。为了找到它,科学家们将检查火山周围的地质地层,致力于挖掘和检查旧爆发的遗骸。冰岛雷克朗斯半岛的最后一次爆发已经发生在800年前,在现代科学出现之前。但由于这种侦探工作,科学家知道爆发始终相对宁静。如果最近的爆发历史可用,那么一个由科学家们实时记录的,一切都更好;这就是为什么科学家知道LaSoufrière可能会从爆炸性的喷发风格的波动迅速切换。

关于爆发预测的最新工作远远超出了这些历史目录。采取Stromboli,一座勉强粘在Tyrrhenian海的水上。如此美丽的岛屿花费了大部分时间爆炸 - 通常伤害没有人的小爆炸。在研究它如何改变两十年的形状之后,RIPEPE和他的同事已经确定它在爆炸之前膨胀。此外,形状的确切变化揭示了爆炸是主要还是未成年人。自2019年10月以来,火山有一个预警系统。它可以检测到最极端爆炸的通货膨胀类型,这一排序在过去杀死了人们,在爆炸到达前10分钟。

Stromboli是一种相对简单的火山,其中,其中从岩浆到天窗上面的管道仍然是开放的。 “岩浆运动不会产生任何裂缝。它刚刚出现,“Ripepe说。

大多数火山更复杂:他们含有各种各样的岩浆类型,需要强迫从火山出路。这意味着他们产生了爆发,“北卡罗来纳州立大学的火山学家Arianna Soldati说,”改变了很多。“。在几天,周,几个月或几年的过程中,喷发可以在渗出和爆炸之间来回来回。是否有可能预测这些变化?

Soldati,罗马和他们的同事发现了一种通过观察夏威夷大岛来测试这一点。自1983年以来,在岛屿的东南海岸附近的kīlauea一直在不断爆发某种形式。但在2018年春季和夏天,火山展出了一个展示:山顶的熔岩湖耗尽,好像有人从浴缸中拉了插头;岩浆在地下到了地球的东侧,撕开了地球的开放裂缝,直接涌出了三个月,有时射击天空作为熔岩的高出喷泉。

正如这种情况发生,研究人员采用了熔岩样品,特别是一个特征:粘度。 Ploopier,贴上岩浆陷阱更多气体。当这种粘性岩浆到达表面时,它的气体猛烈地减压,产生爆炸。相比之下,达尔尼尔岩浆使天然气逐渐逃脱,就像一张桌子上无人看管的苏打水一样。

2018年,熔岩粘度在Kīlauea上保持不断变化。较旧的,较冷的岩浆更粘稠,而来自深度的新敲击岩浆更热,更流体。

罗马和同事发现,他们可以通过监测从火山出现的地震波并将它们与他们采样的熔岩的不同粘度进行比较来跟踪这些变化。出于尚未确定的原因,作为runnier岩浆升削,它迫使岩石墙在其两侧略微分开。相比之下,Gloopier岩浆施加强大的力量,推动开放的途径。在一篇论文本质上,研究人员表明,他们可以使用地震波,这取决于岩石被强制开放的方式,预测岩浆爆发前爆发的熔岩粘度小时数的变化。

“找到了一些告诉我们的东西,是的,如果你有这种地震性,粘度正在增加,如果它高于这个门槛,它可能会更爆炸 - 这是超级酷,”萨德拉蒂说。“ “对于监测和危害,这实际上有可能产生影响。”

许多因素会影响岩浆粘度。特别是一个忽略了一个,主要是因为它几乎看不见。

德国Bayreutub大学的地球科学家Danilo di Genova,研究纳米晶体晶体,大约是平均细菌的百分之一的晶体。当岩浆涌出它时,他们被认为在导管的顶部形成。如果获得足够的这些晶体,它们可以锁定岩浆,监禁捕获的气体,并增加粘度。但除非你有非常强大的显微镜看,才能看新爆发的熔岩,除非他们将是难以察觉的。

Di Genova长期以来一直对纳米岩层的形式感兴趣。他的实验使用硅油 - 一种玄武岩代理,一个普遍的流坠的岩浆 - 表明,如果仅3%的油颗粒混合物由纳米尺寸颗粒制成,粘度尖峰。

然后他转向真实的东西。他和他的同事试图模拟麦克马在通过导管到表面上升时的体验。它们使实验室熔化的玄武岩岩石从埃特纳山逐渐加热,突然冷却,水合和脱水的脉冲。有时,它们将岩浆放置在同步rotron内,一种粒子加速器。在这种对手内,功能强大的X射线与水晶原子相互作用,以揭示其性质,并且如果晶体足够小 - 它们存在。

如去年的科学推进所报道,实验给了团队的工作模型如何形成南冰石的形式。如果爆发开始,岩浆突然通过导管加速,它迅速减轻了。让水从熔岩中出来并形成气泡,使岩浆脱水。

这种动作改变了岩浆的热特性,使得即使在极高的温度下也具有很大的晶体。如果岩浆的上升足够快,并且岩浆速度迅速脱水,则纳米岩石的聚宝盆也表现出来,这显着增加了岩浆的粘度。

这种变化不会放弃一个明显的信号。但是,只要知道它存在,Di Genova,可以使研究人员解释为什么利用VESUVIUS或ETNA这样流行的岩浆火山,有时可以产生史诗般的爆炸。地震信号可以追踪岩浆上升的速度如何,因此可能用于预测最后一分钟的纳米人口繁荣,导致灾难性的爆炸。

除了这些预付款,科学家们仍然是替代爆发概率的延迟。

一个原因是“世界上大多数的火山都没有得到很好的监测,”美国地质调查级联火山天文台的研究地震学家Seth Moran说。这包括许多美国的级联火山,其中一些具有巨大爆炸的倾向。 “如果地面上有足够的仪器,则不易预测喷发,”罗马说。 “但如果火山上没有乐器,那么非常难以预测爆发。”

另一个问题是,一些爆发目前没有明确切割的前体。一种臭名昭着的类型被称为潜水爆炸:岩浆烹饪覆盖的水袋,最终触发压力烹饪器的爆炸。 2019年12月摇晃了新西兰的Whakaari火山,杀死了22人来到小岛。另一个震动了日本的宣传火山2014年,杀死了63名徒步旅行者。

最近由Alaska大学的地球物理主义者领导的一项研究,Fairbanks,Fairbanks,发现卫星可以检测逐渐升级,在热辐射中逐渐增加,在突然爆发中脱离各种火山。回顾性分析表明,在对2014年的2014潜超爆炸之前检测到这种温度升高,围绕事件时间的峰值。

也许从太空监测将成为看到未来潜水的最佳方式。但到目前为止,没有成功的潜水爆发的长期预测。 “潜水爆发是可怕的,”西华盛顿大学的火山科学家和地震学家Jackie Caplan-Auerbach说。 “你真的不知道他们来了。”

这不仅仅是爆炸,可以证明预测棘手。刚果民主共和国的山地火山,突然在今年5月22日突然爆发了一座多山火山,向戈马市泄漏了快速移动的熔岩。尽管被监控,火山没有明确的警告即将爆发,几位人丧生。

无论您预测什么类型的爆发,假阳性的价格都是瘫痪。 “当你疏散人物而且没有什么发生的,那么下一次疏散会使人们认真对待人们更加困难,”罗马说。

但有理由乐观。科学家们比以往任何时候都更好地抓住所有火山的物理学。牛津大学的火山学家David Pyle说,单个火山也变得更加熟悉。很快,他预测,机器学习程序,能够比任何人更快地识别数据的模式,将成为一个主要的球员。

爆发预测的确定性 - 如果,何时或如何 - 可能永远不会通过。但是,日复一日,潜在的致命雾的不确定性稍微消散了一点,而且几十年前在爆发期前会去世的人现在已经活着。


英文译文:

Last December, a gloopy ooze of lava began extruding out of the summit of La Soufrière, a volcano on the Caribbean island of St. Vincent. The effusion was slow at first; no one was threatened. Then in late March and early April, the volcano began to emit seismic waves associated with swiftly rising magma. Noxious fumes vigorously vented from the peak.

Fearing a magmatic bomb was imminent, scientists sounded the alarm, and the government ordered a full evacuation of the island’s north on April 8. The next day, the volcano began catastrophically exploding. The evacuation had come just in time: At the time of writing, no lives have been lost.

Simultaneously, something superficially similar but profoundly different was happening up on the edge of the Arctic.

Increasingly intense tectonic earthquakes had been rumbling beneath Iceland’s Reykjanes Peninsula since late 2019, strongly implying that the underworld was opening up, making space for magma to ascend. Early in 2021, as a subterranean serpent of magma migrated around the peninsula, looking for an escape hatch to the surface, the ground itself began to change shape. Then in mid-March, the first fissure of several snaked through the earth roughly where scientists expected it might, spilling lava into an uninhabited valley named Geldingadalur.

Here, locals immediately flocked to the eruption, picnicking and posing for selfies a literal stone’s throw away from the lava flows. A concert recently took place there, with people treating the ridges like the seats of an amphitheater.

In both cases, scientists didn’t just accurately suggest a new eruption was on its way. They also forecast the two very different forms these eruptions would take. And while the “when” part of the equation is never easy to forecast, getting the “how” part right is especially challenging, especially in the case of the explosive eruption at La Soufrière. “That’s a tricky one, and they nailed it, they absolutely nailed it,” said Diana Roman, a volcanologist at Carnegie Institution for Science.

Volcanologists have developed an increasingly detailed understanding of the conditions that are likely to produce an explosive eruption. The presence or absence of underground water matters, for instance, as does the gassiness and gloopiness of the magma itself. And in a recent series of studies, researchers have shown how to read hidden signals—from seismic waves to satellite observations—so that they may better forecast exactly how the eruption will develop: with a bang or a whimper.

As with skyscrapers or cathedrals, the architectural designs of Earth’s volcanoes differ wildly. You can get tall and steep volcanoes, ultra-expansive and shallowly sloped volcanoes, and colossal, wide-open calderas. Sometimes there isn’t a volcano at all, but chains of small depressions or swarms of fissures scarring the earth like claw marks.

Eruption forecasting asks a lot of questions. Chief among them is: When? At its core, this question is equivalent to asking when magma from below will travel up through a conduit (the pipe between the magma and the surface opening) and break through, as lava flows and ash, as volcanic glass and bombs.

When magma ascends from depth, it can alter a volcano’s architecture, literally changing the shape of the land above. Migrating magma flows can also force rock apart, generating volcano-tectonic earthquakes. And when the pressure keeping magma trapped underground declines, it liberates trapped gas, which can escape to the surface.

Eruption forecasters look for any of those three signs: changes in a volcano’s shape, its seismic soundscape, or its outgassing. If you spy changes in all three—changes that are clearly very different from the volcano’s everyday behavior—then “there is no doubt that something is going to happen,” said Maurizio Ripepe, a geophysicist at the University of Florence in Italy. That something is often, eventually, an eruption.

Change doesn’t always mean an uptick in activity. Most volcanoes get noisier and twitchier before erupting, but sometimes the opposite is true. Seismologists in Iceland, for example, recorded a drop in volcanic tremor immediately prior to the opening of Reykjanes’ first five fissures. When the sixth drop happened, said Thorbjörg Ágústsdóttir, a seismologist at Iceland GeoSurvey, scientists forecast that a sixth fissure was about to appear—and they were right.

Increasingly, it’s also possible to forecast not just when or if a volcano will erupt, but how.

Unspooling the history of each specific volcano is key, as individual volcanoes tend to have their own eruptive style. To find it, scientists will examine the geological strata around a volcano, forensically exhuming and examining the remains of old eruptions. The last eruption on Iceland’s Reykjanes Peninsula had occurred 800 years ago, long before the advent of modern science. But because of this sort of detective work, scientists knew that the eruptions there have always been relatively tranquil affairs. If a recent eruption history is available, one documented in real time by scientists, all the better; that’s why scientists knew La Soufrière was likely to speedily switch from an effusive to an explosive eruption style.

The latest work on eruption forecasting goes far beyond these historical catalogs. Take Stromboli, a volcano barely sticking above the waters of the Tyrrhenian Sea. This picturesque isle spends much of its time exploding—usually small blasts that harm no one. After studying how it changes shape for two decades, Ripepe and his colleagues have determined that it inflates just before it explodes. Moreover, the exact change in shape reveals whether the blast will be major or minor. Since October 2019, the volcano has had an early warning system. It can detect the type of inflation indicative of the most extreme explosions, the sort that have killed people in the past, up to 10 minutes before the blast arrives.

Stromboli is a relatively simple volcano, though, one in which the plumbing from the magma to the skylight up top remains more or less open. “The magma movement does not generate any fractures. It just comes up,” Ripepe said.

Most volcanoes are more complicated: They harbor a diverse array of magma types that need to force their way out of the volcano. That means they produce eruptions that “change a lot as they happen,” said Arianna Soldati, a volcanologist at North Carolina State University. Over the course of days, weeks, months, or years, an eruption can go back and forth between oozing and exploding. Is it possible to forecast these changes?

Soldati, Roman, and their colleagues found a way to test this by looking to the Big Island of Hawaii. Kīlauea, near the island’s southeastern coast, had been continuously erupting in some form or another since 1983. But in the spring and summer of 2018, the volcano put on a hell of a show: The lava lake at its summit drained away, as if someone had pulled the plug from a bath; magma made its way underground to the eastern flanks of the volcano and tore open cracks in the earth, gushing out of them for three months straight, sometimes shooting skyward as tall fountains of molten rock.

As this happened, the researchers took lava samples, concentrating on one feature in particular: viscosity. Gloopier, stickier magma traps more gas. When this viscous magma reaches the surface, its gas violently decompresses, creating an explosion. Runnier magma, by contrast, lets gas escape gradually, like a soda left unattended on a table.

In 2018, the viscosity of the lava on Kīlauea kept changing. Older, colder magma was more viscous, while newly tapped magma from depth was hotter and more fluid.

Roman and colleagues discovered that they could track these changes by monitoring the seismic waves emerging from the volcano and comparing them with the varying viscosity of the lava they sampled. For reasons yet to be determined, as runnier magma ascends, it forces the rocky walls on either side of it only a little bit apart. Gloopier magma, by contrast, exerts a strong force, pushing open a wider pathway. In a paper published this April in Nature, the researchers showed that they could use seismic waves, which differed depending on the way the rock was forced open, to forecast the change in the erupted lava’s viscosity hours to days in advance of that magma’s eruption.

“Having found something that tells us, yes, if you have this kind of seismicity, viscosity is increasing, and if it’s above this threshold, it could be more explosive—that is super cool,” said Soldati. “For monitoring and hazards, this actually has the potential to be impactful now.”

Many factors influence magma viscosity. One in particular has been overlooked, mostly because it’s nearly invisible.

Danilo Di Genova, a geoscientist at the University of Bayreuth in Germany, studies nanolites—crystals about one-hundredth of the size of your average bacterium. They are thought to form at the top of the conduit as magma gushes up it. If you get enough of these crystals, they can lock up the magma, imprison trapped gas, and increase the viscosity. But unless you have very powerful microscopes to look at freshly erupted lava, they’ll be imperceptible.

Di Genova has long been interested in how nanolites form. His experiments using silicon oil—a proxy for basalt, a commonplace runny magma—showed that if just 3 percent of an oil-particle mixture is made of nano-size particles, the viscosity spikes.

He then turned to the real thing. He and his colleagues attempted to simulate what magma would experience as it rose through a conduit to the surface. They subjected lab-melted basaltic rock from Mount Etna to gradual heating, pulses of sudden cooling, hydration, and dehydration. At times, they placed the magma inside a synchrotron, a type of particle accelerator. Within this contraption, powerful x-rays interact with a crystal’s atoms to reveal their properties and—if the crystals are small enough—their existence.

As reported last year in Science Advances, the experiments gave the team a working model of how nanolites form. If an eruption begins and magma suddenly accelerates up through the conduit, it rapidly depressurizes. That lets water come out of the molten rock and form bubbles, which dehydrates the magma.

This action changes the thermal properties of the magma, making it a lot easier for crystals to be present even at extremely high temperatures. If the magma’s ascent is sufficiently rapid and the magma is speedily dehydrated, a cornucopia of nanolites comes into being, which significantly increases the magma’s viscosity.

This change doesn’t give off a noticeable signal. But merely knowing it exists, said Di Genova, may enable researchers to explain why volcanoes with otherwise runny magma, like Vesuvius or Etna, can sometimes produce epic explosions. Seismic signals can trace how quickly magma is ascending, so perhaps that may be used to forecast a last-minute nanolite population boom, one that leads to a catastrophic blast.

These advances aside, scientists are still a long way from replacing eruption probabilities with certainties.

One reason is that “most of the world’s volcanoes are not that well monitored,” said Seth Moran, a research seismologist at the US Geological Survey’s Cascades Volcano Observatory. This includes many of America’s Cascades volcanoes, several of which have a propensity for giant explosions. “It’s not easy to forecast an eruption if there are sufficient instruments on the ground,” said Roman. “But it’s very, very difficult to forecast an eruption if there are no instruments on the volcano.”

Another problem is that some eruptions currently have no clear-cut precursors. One notorious type is called a phreatic blast: Magma cooks overlying pockets of water, eventually triggering pressure-cooker-like detonations. One rocked New Zealand’s Whakaari volcano in December 2019, killing 22 people visiting the small island. Another shook Japan’s Ontake volcano in 2014, killing 63 hikers.

A recent study led by Társilo Girona, a geophysicist at the University of Alaska, Fairbanks, found that satellites can detect gradual, year-over-year upticks in the thermal radiation coming off all sorts of volcanoes in the run-up to an eruption. A retrospective analysis showed that such a temperature increase was detected before Ontake’s 2014 phreatic explosion, with a peak around the time of the event.

Perhaps monitoring from space will become the best way to see future phreatic eruptions coming. But so far, no successful long-term forecast of a phreatic eruption has taken place. “Phreatic eruptions are terrifying,” said Jackie Caplan-Auerbach, a volcanologist and seismologist at Western Washington University. “You really don’t know they’re coming.”

It’s not just explosions that can prove tricky to forecast. Nyiragongo, a mountainous volcano in the Democratic Republic of Congo, suddenly erupted on May 22 of this year, spilling fast-moving lava toward the city of Goma. Despite being monitored, the volcano gave no clear warning it was about to erupt, and several people perished.

And no matter what type of eruption you are forecasting, the price of a false positive is crippling. “When you evacuate people and nothing happens, then the next evacuation is going to be orders of magnitude more difficult to get people to take seriously,” said Roman.

But there are reasons to be optimistic. Scientists are grasping the physics underlying all volcanoes better than ever. Individual volcanoes are also becoming more familiar because of “a mixture of instinct and experience and learned knowledge,” said David Pyle, a volcanologist at the University of Oxford. Soon, he predicts, machine learning programs, capable of identifying patterns in data faster than any human, will become a major player.

Certainty in eruption forecasting—the if, when or how—will probably never come to pass. But day by day, the potentially deadly fog of uncertainty dissipates a little more, and someone who would have died a few decades ago during an eruption now gets to live.


Share this Post:

相关资讯: