内容来源：https://www.quantamagazine.org/when-quiet-undersea-volcanoes-turn-disruptive-20260526/

内容总结：

深海“沉默火山”或颠覆认知：研究发现海底火山可发生剧烈喷发

2024年6月，一艘名为“流星号”的德国科考船在北大西洋冰岛附近海域执行M201航次任务时，意外发现了一处异常的海底火山地貌。这批来自汉堡大学等机构的科学家原本只是测试地球物理设备，却在雷克雅内斯海岭（大西洋中脊的一段）获取了令人费解的地震剖面图像——与通常粗糙崎岖的海底火山地形不同，这里出现了顶部平坦、坡度陡峭的平滑山丘，四周还散落着疑似海面以上喷发形成的碎屑物。

这一发现挑战了科学界对洋中脊火山的传统认知。通常，在2500米以下的深海，巨大水压抑制了火山气体的膨胀，使洋中脊火山多以缓慢溢流方式活动，鲜少发生剧烈爆炸。但研究发现，当水深降至约300米时，这种抑制作用显著减弱。研究团队认为，这正是1963年冰岛叙尔特塞岛（Surtsey）突然从海面“凭空出现”的成因：较浅的水压使海水与岩浆接触后瞬间汽化，引发足以突破海面的爆炸式喷发。

这些顶部被削平的海底火山并非冰川作用形成。尽管约2万年前冰岛曾被冰川覆盖，但分析显示，火山物质堆积在废弃的冰川碎石之上，表明喷发发生在冰川消退之后。研究牵头人、现就职于英国国家海洋学中心的约纳斯·普赖纳博士指出，北大西洋风暴海浪的侵蚀作用将这些火山削平至海面下约40米的统一深度，恰好印证了这一深度是关键控制参数。

研究还暗示，冰川消退可能间接引发了火山活动激增。当冰盖融化后，对地壳的压制作用消失，如同释放了“弹簧”，可能导致火山喷发频率显著增加。这一假设若能通过后续岩石采样和年代测定证实，将彻底改变对洋中脊火山活动规律的理解。

目前，从亚速尔群岛到加拉帕戈斯群岛直至红海，全球多处浅水段洋中脊均存在类似的喷发条件。尤其值得关注的是，自2020年以来，冰岛雷克雅内斯半岛（雷克雅内斯海岭的陆上延伸部分）下方一个巨大岩浆房持续膨胀，已导致地震频发、岩浆涌上街道，城镇格林达维克约3700名居民被迫疏散。普赖纳坦言：“再次出现类似叙尔特塞岛喷发的可能性并不低。”今年1月，该海岭区域还记录到了一次小规模地震群。

中文翻译：

当寂静的海底火山变得躁动不安
引言
2024年6月，汉堡大学新晋博士乔纳斯·普赖恩在北大西洋冰岛附近一艘颠簸的科考船实验室里，眯眼看着电脑屏幕。眼前的图像完全不符合常理。

他所在的科研团队刚从雷克雅未克出发，顶着铅灰色的天空，告别家人、朋友和日常办公环境，挤进“流星号”科考船狭小的船舱——这艘船被包租用于M201次考察——还要忍受晕船的折磨。幸运的是，前往目的地途中海面相对平静。他们的目标是那片从未被探索的深海盆地，海底散布着火山地形。研究人员携带了大量设备：用于采集地球内部地震剖面的地球物理仪器、拍摄海底的相机，以及用于采集岩石样本、验证模糊且仅经部分处理的电脑图像信息的取芯和挖泥设备。

首个傍晚，在距港口约100公里处，团队在浅水区暂停作业以测试地球物理设备。他们采集的海底分层结构地震图像，将引出一个出乎意料的发现——这一发现会颠覆我们对海底通常缓慢活动的火山裂缝的认知。这些发现还可能关联到历史上那些神秘的“幽灵岛”：目击者称它们突然浮现，随后又沉入波涛之下。

在实验室里，普赖恩截了几张图分享给团队。六周后考察归来，他几乎不费吹灰之力便说服项目首席科学家在浅水区停留，以探查他们的发现。

熔岩传送带
冰岛在地质学上堪称罕见。在这座全球最大的火山岛上，你可以徒步穿行于分隔北美板块与欧亚板块的峡谷之间。

这是因为冰岛坐落在大洋中脊之上——一条地壳撕裂、海洋随扩张空间增长的巨大缝合带。大西洋中脊始于约2亿年前三叠纪末期泛大陆分裂之时；而冰岛的形成则晚得多，当时一股异常炽热的地幔岩流将中脊拱起，露出海面。

全球的大洋中脊都不以剧烈喷发著称——完全不像华盛顿州爆炸性的圣海伦斯火山，或摧毁庞贝与赫库兰尼姆的意大利南部维苏威火山。因此，“流星号”团队驶过雷克雅内斯海脊（大西洋中脊的一段水下部分）时，并未指望发现异常。他们只想确认设备运转正常。

团队启动设备，传回的X光般图像显露出海底岩层的剖面。“我们决定在雷克雅内斯海脊做两次测试剖面，因为操作方便且可能有趣，”普赖恩说——他如今是英国国家海洋学中心的海洋地球物理学家。

大洋中脊的地震图像通常显示粗糙崎岖的地形，这是熔岩沿断层或裂缝渗入寒冷海水后骤然凝固形成的。但普赖恩看到的并非如此。海脊沿线分布着陡坡平顶的圆滑丘体，侧翼覆盖着散落的沉积物，看起来像是海面以上喷发留下的碎屑。这些地形让他想起博士论文的主题——希腊圣托里尼岛附近一个以剧烈喷发闻名的水下火山系统。

为何在通常平静的大洋中脊会出现爆炸性火山？它们的顶部又为何被削平？

昙花一现的幻影
浩瀚深邃的海洋大部分仍未勘探。世世代代，科学家研究深海的主要手段不过是拖网取样，用拖斗捞取能获得的一切。直到近几十年，地球物理技术与深海摄像机才让人们得以一窥这些神秘世界。

“海洋中的火山喷发次数其实多于陆地，”英国国家海洋学中心的火山学家伊索贝尔·尤说（她未参与M201次考察），“我们对它们的了解实在太少了。”

以下是我们已知的：在全球大部分海域，深渊的 crushing 压力抑制了大洋中脊的爆炸性喷发。大西洋中脊大部分位于海平面以下至少2500米处，极端压力使火山气体无法膨胀，喷发仅限于熔岩的安静溢流。

考察队返回后，更多剖面和成像数据表明，他们无意中发现了这种抑制解除的边界：大西洋中脊在约300米深度处改变了性质。这一转变或许能解释冰岛近代史上的一次事件。

1963年11月14日，毫无预兆地，雷克雅内斯海脊上方冰冷漆黑的海水中冒出了新陆地。三年间，一座火山岛喷射喷涌，最终高出海平面171米。冰岛政府将其命名为叙尔特塞岛，取自北欧神话中的火神苏尔特尔。

历史上，所谓的“幽灵岛”（多为火山成因）偶尔会引发慌乱甚至戏剧性的主权宣称与海军对峙。“曾有滑稽的报道称，皇家海军在它们露出海面时插上旗帜，随后却眼睁睁看着它们被海浪侵蚀消失，”曼彻斯特大学地球物理学家尼尔·米切尔在邮件中写道。

这些幽灵岛中，有些诞生于更活跃的火山带，但包括叙尔特塞岛在内的其他岛屿，则神秘地出现在缓慢溢流的大洋中脊沿线。历史记录显示，过去1000年间，雷克雅内斯海脊北部至少发生过14次喷发。

普赖恩和同事们认为，他们找到了解释叙尔特塞岛及观察到的奇异海底火山的统一理论。他们能精确指出一个特定深度：在此处，压力刚好减弱到足以让与熔岩接触的海水瞬间汽化，从而驱动能冲破海面的爆炸性喷发。

覆盖在火山陡坡上的沉积物是关键线索，普赖恩说。水会抑制碎屑的飞散距离——这点任何人尝试在水下抛掷物体都能证实。因此，水下喷发的物质会堆积在喷发口附近。然而，一旦火山冲破海面，火山灰和岩石碎屑就能散播得更远。这个过程可能持续数日、数月甚至数年。直到岩浆房耗尽，海浪重新接管一切。

在冰岛，海洋是一股强大的力量。普赖恩表示，该地区水下平顶火山被侵蚀至海平面以下约40米的统一深度——他认为这并非巧合，因为北大西洋风暴浪的侵蚀作用仅能达到这个深度。“这里的关键参数是深度，”加州大学圣迭戈分校斯克里普斯海洋研究所的地球物理学家罗斯·帕内尔-特纳说（他未参与M201次考察）。

较低的水压与大西洋海浪的侵蚀力似乎能解释M201次考察的观测结果。但还有另一个因素需要考虑。

冰之国度
保尔·埃纳尔松清晰记得1963年叙尔特塞岛开始喷发的那一天。他那对火山充满好奇的工程师父亲驱车带他前往机场——老埃纳尔松说服一位飞行员临时飞过新火山。从飞机上，年轻的埃纳尔松目睹黑色烟柱从无尽的北海中升起。

埃纳尔松后来主要研究火山学，如今是冰岛大学的地球物理学荣誉教授。当被问及M201次考察的发现时，他表示团队的努力令人印象深刻，但对平顶火山形成理论并不完全信服。因为出于不同原因，类似的火山既出现在深海也出现在陆地。

约2万年前，冰岛被缓慢移动的冰川覆盖。如今，冰川仍覆盖着该国约11%的面积，而冰川退却后的区域分布着被称为“图雅”（或桌山）的矮火山。一些科学家认为，当上升的岩浆撞上厚实的冰盖并融化冰层引发爆炸时，便形成了图雅。但冰川就像蘑菇丛上方压着的石板，阻止火山长得太高。

末次冰期时，海平面远低于现今，冰岛的冰川延伸至裸露的雷克雅内斯海脊。冰川推进的范围似乎大致达到了如今海平面以下约300米处——正是M201次考察发现平顶火山的区域。研究团队最初怀疑这些水下丘体是否是被淹没的图雅。

但他们确实找到了反驳冰川理论的证据：火山物质似乎堆积在废弃的冰川碎石之上，表明喷发发生在冰川退缩之后。本文采访的大多数外部专家表示，这些观测结果足以排除冰川理论，但埃纳尔松希望看到更多证据。

科学家清楚解决争议需要什么：岩石样本，或至少通过潜水器好好观察一番。

对于爆炸性海底喷发，“就像有人把一卡车火山沙倾倒在所有东西上，”马萨诸塞州伍兹霍尔海洋研究所的地球物理学家罗伯特·索恩说（他未参与此项研究），“一眼就能看出来。”但普赖恩团队仅从该区域的海底拖网获得了有限物质，缺乏足够的直接视觉证据来证实其理论。

然而，收集新证据需要时间——深海勘探计划通常提前数年制定。“你根据地图上某个人标的一点驶向茫茫大海，非常希望他们标对了位置，”尤说，“你只能接受过去的自己所做的决定。”

普赖恩保持开放态度。他并不急于否定冰川的影响，尽管认为其作用方式可能不同。与海水一样，冰盖也会对地壳施加压力，抑制火山活动。当冰盖退缩（如在雷克雅内斯海脊发生的那样），压力随之释放，导致火山活动激增。普赖恩表示，采集岩石样本测定火山年代，对于检验一个仍属工作假说的观点“将极其有趣”——即冰川消退间接开启了新的火山活跃期。

过去的喷发与未来的喷发
正如叙尔特塞岛生动证明的那样，在合适条件下，大洋中脊的喷发方式会从平静转为爆炸性。科学家如今怀疑，过去这种情况可能更常见——并且想知道何时会再次发生。

无论研究人员对大西洋中脊有何新发现，其模式可能远不止冰岛一地。从亚速尔群岛到加拉帕戈斯群岛再到红海，浅水区的大洋中脊都跨越了同样的深度阈值。在这些地方，深部缓慢的“传送带”可能偶尔让位于更剧烈的活动，形成短暂露出海面、随后又被海浪磨平的岛屿。

不过，冰岛仍有理由受到特别关注。自2020年左右以来，雷克雅内斯半岛（雷克雅内斯海脊的陆上延伸部分）下方一个巨大的岩浆房持续膨胀，引发地震并导致熔岩侵入街道。2023年，渔村格林达维克的约3700名居民被疏散，许多人或许再也不能返回。

如今科学家表示，压力再次积聚。“我们此刻正处在一场非常显著的事件的中心，”埃纳尔松说。

在近海区域，大部分活动仍隐匿不见。但同样的力量正在作用，普赖恩说，而“另一个叙尔特塞岛再次升起的概率并不低”。普赖恩在1月份表示：“一位同事发邮件说，本周雷克雅内斯海脊实际上发生了一次地震群。不算大，但谁知道呢。”

英文来源：

When Quiet Undersea Volcanoes Turn Disruptive
Introduction
Jonas Preine, a recently minted Ph.D. from the University of Hamburg, squinted at a computer screen in the lab of a ship as it bobbed in the North Atlantic near Iceland. The image before him just didn’t make sense.
It was June 2024, and Preine was among a crew of scientists who had set off from Reykjavik under slate-colored skies, trading their regular lives — family, friends, and the typical office environment — for cramped quarters and nausea on board the Meteor, a research vessel chartered for Expedition M201. They’d been lucky so far, enjoying relatively calm seas as they motored toward their destination, an unexplored deep-water basin dotted with volcanic shapes. The researchers carried reams of equipment: geophysical tools to collect seismic profiles of the Earth’s interior, cameras to image the ocean floor, and coring and dredging equipment to sample rocks and verify what might appear in grainy, partially processed computer images.
That first evening, about 100 kilometers from port, the team paused to test their geophysical tools in shallow waters. The seismic imagery they collected of the seafloor’s layered interior would lead them to an unexpected discovery, one that would complicate what we know about the usually sluggish volcanic fissures that lace the bottom of the ocean. Their findings could also be connected to mysterious islands from the recesses of history that witnesses said appeared suddenly, only to disappear later beneath the waves.
In the lab, Preine snapped some screenshots and shared them with the team. Six weeks later, on returning from the expedition, he needed little effort to convince the project’s lead scientist to stop in shallow waters to investigate what they’d found.
A Conveyor Belt of Lava
Iceland is a geological rarity. Here, on the world’s largest volcanic island, you can hike through gorges dividing the North American and Eurasian tectonic plates.
That’s because Iceland sits on a mid-ocean ridge, a vast seam where Earth’s crust tears apart and oceans grow in the expanding space between. The Mid-Atlantic Ridge began forming about 200 million years ago, as the supercontinent Pangaea broke apart at the end of the Triassic Period. Iceland emerged much later when a plume of unusually hot mantle rock arched the ridge up above the gathering waves.
Across the globe, mid-ocean ridges have a nondramatic style — nothing like Washington State’s explosive Mount St. Helens or southern Italy’s Mount Vesuvius, the destroyer of Pompeii and Herculaneum. So the team aboard the Meteor wasn’t expecting anything unusual when they passed over a submerged segment of the Mid-Atlantic Ridge called the Reykjanes Ridge. They just wanted to confirm that their equipment was in working order.
The crew switched the equipment on, pinging back X-ray-like images that revealed layers of the seafloor’s stone interior. “We decided to do two test profiles over the Reykjanes Ridge because it was logistically easy and potentially interesting,” said Preine, now a marine geophysicist at the National Oceanography Center in England.
Seismic images of mid-ocean ridges typically show rough and jagged terrain, formed when lava oozes up into the cold ocean along faults or fissures and hardens suddenly into stone. But that’s not what Preine saw. Along the ridge were smooth mounds with steep sides and flat tops, their flanks draped in scattered deposits that looked like debris from an eruption above the sea surface. The formations reminded him of the topic of his doctoral dissertation, a submerged system of notoriously explosive volcanoes near Santorini, Greece.
Why did there seem to be explosive volcanoes along the usually quiet mid-ocean ridge? And why were their tops beveled flat?
A Fleeting Apparition
Oceans, vast and deep, remain largely unexplored. For generations, scientists could do little more to study the depths than dredge the seafloor, dragging buckets for whatever they could find. Only in recent decades have geophysical technology and deep-sea cameras provided glimpses of these mysterious worlds.
There are more volcanic eruptions in the oceans than on land, said Isobel Yeo, a volcanologist at the National Oceanography Center who was not involved in Expedition M201. “We just don’t know nearly as much about them.”
Here’s what we do know: Across most of the globe, the crushing weight of the abyss suppresses explosive eruptions at mid-ocean ridges. Most of the Mid-Atlantic Ridge lies at least 2,500 meters below the sea, where extreme pressure keeps volcanic gases from expanding and limits eruptions to quiet outpourings of lava.
When the expedition returned, more profiles and imaging made it clear that the team had stumbled on the boundary where that restraint lifts: The Mid-Atlantic Ridge changed character at around a depth of 300 meters. That transition could explain an incident from Iceland’s recent history.
Without warning on November 14, 1963, new land emerged from the cold black waters above the Reykjanes Ridge. Over the course of three years, a volcanic island spewed and sputtered as it rose 171 meters above the sea. The government of Iceland named the island Surtsey, after the Icelandic mythic fire god Surtur.
Throughout history, so-called phantom islands — many of them volcanic — have occasionally sparked frantic, even quasi-comedic claims and naval tensions. “There were humorous reports of the Royal Navy stopping to put a flag on them when they breached sea level, only to see them disappear by wave erosion,” wrote Neil Mitchell, a geophysicist at the University of Manchester, via email.
While some of these phantom islands emerged from more volatile volcanic zones, others, including Surtsey, appeared mysteriously along the gently oozing mid-ocean ridge. In total, historical records document at least 14 eruptions on the northern Reykjanes Ridge over the last 1,000 years.
Preine and his colleagues felt they had a unifying explanation for Surtsey and the strange subsea volcanoes they’d observed. They could pinpoint a specific depth at which the pressure eased just enough to allow seawater in contact with lava to flash to steam, powering an explosive eruption that could breach the sea’s surface.
The deposits that blanketed the volcanoes’ steep flanks were critical clues, Preine said. Water dampens how far debris gets thrown, as anyone who has ever tried throwing an object underwater can confirm. So the material from underwater eruptions settles close to its source. Once a volcano breaches the sea surface, though, it can scatter ash and rock debris much farther. This can go on for days, months, or even years. Then, once the magma chamber is exhausted, the sea takes over again.
In Iceland, the sea is a force. Preine said the region’s underwater flat-topped volcanoes are worn down to a uniform depth of around 40 meters below sea level — no coincidence, he argued, since North Atlantic storm-wave erosion only reaches down that far. “The key parameter here is depth,” said Ross Parnell-Turner, a geophysicist at Scripps Institution of Oceanography at the University of California, San Diego, who was not involved in the work of Expedition M201.
The influence of lower water pressure and the force of the Atlantic’s waves seemed to explain Expedition M201’s observations. But there was another factor to consider.
A Land of Ice
Páll Einarsson vividly recalls the day in 1963 when Surtsey began erupting. His father, a volcano-curious engineer, drove him to the airport, where the elder Einarsson had convinced an airline pilot to take an impromptu flight over the new volcano. From the plane, the younger Einarsson watched the plume of dark smoke emerge from the endless northern seas.
Einarsson went on to study volcanoes, among other things, and is now an emeritus geophysicist at the University of Iceland. When asked about Expedition M201’s findings, he said he was impressed by the team’s efforts but not fully convinced of their theory about how the flat-topped volcanoes formed. That’s because, for different reasons, similar volcanoes appear both in the deep ocean and on land.
Some 20,000 years ago, Iceland was covered with slow-moving glaciers. Today, glaciers remain across approximately 11% of the country, and the areas left behind are home to squat mountains called tuyas, or table mountains. Some scientists think the tuyas formed when rising magma collided with a thick ceiling of ice and melted it, triggering explosions. But like a paving stone above a cluster of mushrooms, the glaciers acted like a lid, preventing the volcanoes from growing too tall.
During the last ice age, the sea level was far lower than today, and Iceland’s glaciers extended across the exposed Reykjanes Ridge. That glacial advance appears to have reached roughly the area that now lies beneath about 300 meters of water, where Expedition M201 identified the flat-topped volcanoes. The research team initially wondered whether the submerged mounds could be drowned versions of tuyas.
They did find evidence against the glacier theory: The volcanic material appeared to have accumulated on top of abandoned glacial rubble, suggesting that the eruptions happened after the glaciers retreated. Most outside experts interviewed for this story say they’re convinced that these observations rule out the theory, but Einarsson would like to see more evidence.
Scientists know what they need to resolve this tension: rocks, or at least a good look at them from a submersible vehicle.
With explosive submarine eruptions, “it looks like someone dumped a truckful of volcanic sand over everything,” said Robert Sohn, a geophysicist at the Woods Hole Oceanographic Institution in Massachusetts who was not involved in the work. “It’s immediately obvious.” But Preine and company have only limited material from seafloor dredging in the area and not enough direct visuals to substantiate their theory.
It will take a while to gather new evidence, though, as deep-sea exploration plans are formulated years in advance. “You sail into the middle of nowhere based on a point that somebody put on a map, and you hope very much that they’ve put that point in the right place,” Yeo said. “You’re sort of stuck with the decisions past-you made.”
Preine is keeping an open mind. He’s not so quick to dismiss the influence of ice, though he thinks it may have played a different role. Like seawater, ice exerts pressure on the Earth’s crust, suppressing volcanic activity. When ice sheets retreat, as they did along the Reykjanes Ridge, that pressure is released, causing volcanic activity to spike. Preine said sampling rocks to determine the ages of the volcanoes would be “extremely interesting” in testing what remains a working hypothesis: that receding glaciers indirectly fueled a new volcanic era.
Eruptions Past and Future
As Surtsey so vividly demonstrated, the behavior of mid-ocean ridges can shift from calm to explosive under the right conditions. Scientists now suspect that this may have been more common in the past — and wonder when it could happen again.
Whatever researchers discover about the Mid-Atlantic Ridge, the pattern may extend far beyond Iceland. Shallow stretches of mid-ocean ridges, from the Azores to the Galápagos to the Red Sea, cross the same depth threshold. In those places, the slow conveyor belt of the deep may occasionally give way to something more volatile, building islands that briefly rise above the surface before waves grind them back again.
There’s a reason to give Iceland special attention, though. Since around 2020, a giant magma chamber has swelled under the Reykjanes Peninsula, the onshore limb of the Reykjanes Ridge, triggering earthquakes and sending lava oozing into the streets. In 2023, the fishing town of Grindavík’s about 3,700 residents evacuated, many perhaps for good.
Now scientists say that pressure is building again. “We are really in the middle of a very remarkable event right now,” Einarsson said.
Offshore, most of that activity remains hidden. But the same forces are at work, Preine said, and “the chances are not low” for another Surtsey to rise again. “A colleague sent me an email saying that there was actually an earthquake swarm on the Reykjanes Ridge this week,” Preine said in January. “Nothing big, but you never know.”