Huge landslide created a 500-meter-high tsunami in a major tourist area

巨大山体滑坡在主要旅游区引发 500 米高海啸

At 5:26 am local time on August 10, 2025, a massive wedge of rock with a volume of at least 63.5 million cubic meters detached from a mountain above Alaska’s Tracy Arm fjord. The falling rock plummeted into the deep waters at the terminus of the South Sawyer Glacier and caused an initial 100-meter-high breaking wave that tore across the fjord at speeds exceeding 70 meters a second. When this wave hit the opposite shoreline, it surged up the steep rocks to a height of 481 meters above sea level. 2025 年 8 月 10 日当地时间凌晨 5 点 26 分，阿拉斯加特雷西峡湾（Tracy Arm）上方的一座山体发生崩塌，至少 6350 万立方米的巨大岩楔坠入南索耶冰川（South Sawyer Glacier）末端的深水中。坠落的岩石引发了最初 100 米高的破碎波，以每秒超过 70 米的速度横扫峡湾。当这股波浪撞击对岸时，它沿着陡峭的岩壁向上涌动，达到了海拔 481 米的高度。

“It was the second highest tsunami ever recorded on Earth,” says Aram Fathian, a researcher at the University of Calgary and co-author of a recent Science study that reconstructed this event in detail. “But until now, almost nobody heard about it because it was a near-miss event,” he adds. There were no injuries or fatalities reported following the Tracy Arm fjord tsunami, mostly because it happened early in the morning. But we might not be so lucky next time. “这是地球上有记录以来第二高的海啸，”卡尔加里大学研究员、近期发表在《科学》杂志上详细重建该事件的研究报告合著者阿拉姆·法西安（Aram Fathian）表示。“但直到现在，几乎没人听说过它，因为它是一次‘险些酿成大祸’的事件。”他补充道。由于特雷西峡湾海啸发生在清晨，目前没有人员伤亡报告。但下次我们可能就不会这么幸运了。

Landslide megatsunamis

山体滑坡引发的巨型海啸

Earthquake-generated tsunamis usually reach runup heights of a few tens of meters when they strike land. Landslide tsunamis, like the one that happened in Tracy Arm, are often more localized but also way more violent. When millions of tons of rock suddenly fall into a confined body of water like a narrow fjord, the variation in water depth and the direct displacement of the water column produce extremely high waves. Since 1925, scientists have documented 27 such events with runups exceeding 50 meters. The highest was the 1958 Lituya Bay tsunami, which reached 530 meters. 地震引发的海啸在登陆时，爬高通常只有几十米。像特雷西峡湾这样由山体滑坡引发的海啸，往往影响范围更局限，但破坏力却大得多。当数百万吨岩石突然坠入狭窄峡湾等封闭水域时，水深的变化和水柱的直接位移会产生极高的波浪。自 1925 年以来，科学家记录了 27 起此类爬高超过 50 米的事件。最高的一次是 1958 年的利图亚湾（Lituya Bay）海啸，其高度达到了 530 米。

The source of the 2025 Tracy Arm tsunami was a steep rock wedge on the northern side of the fjord. Its headscarp, the uppermost boundary of a landslide or rockfall, sat roughly 1,025 meters above sea level. For centuries, the structural integrity of this slope was maintained by a massive wall of ice known as the South Sawyer Glacier. But South Sawyer, like many other glaciers in the Stikine Icefield, has been in a state of retreat due to the warming climate. 2025 年特雷西峡湾海啸的源头位于峡湾北侧的一块陡峭岩楔。其崩塌顶缘（山体滑坡或落石的最上边界）位于海拔约 1025 米处。几个世纪以来，该斜坡的结构完整性一直由被称为南索耶冰川的巨大冰墙维持。但与斯蒂金冰原（Stikine Icefield）中的许多其他冰川一样，南索耶冰川因气候变暖一直处于退缩状态。

Climate-driven disaster

气候驱动的灾难

“We studied the event from several aspects, from different lenses,” Fathian says. The team used high-resolution satellite images taken before and after the event to reconstruct the shape and geometry of the slide, as well as its axis and direction. Satellite images were also used to evaluate glacial thinning in the area, which, the team concluded, was the root cause of the Tracy Arms event. The collapse, according to the study, was made more likely by the industrial-era warming of the planet. “我们从多个方面、不同的视角研究了这一事件，”法西安说。研究团队利用事件发生前后的高分辨率卫星图像，重建了滑坡的形状和几何结构，以及其轴线和方向。卫星图像还被用于评估该地区的冰川变薄情况，研究团队得出结论，这是导致特雷西峡湾事件的根本原因。研究指出，工业时代全球变暖使得此次崩塌发生的可能性大大增加。

Researchers calculating the regional temperature trends found a 1.1° C increase in summertime temperatures since around 1875, driving up snowline elevations by roughly 169 meters. The local ice also got significantly thinner. Between 2013 and 2022 alone, the glacier ice bracing the failure site thinned by 100 to 130 meters. Without millions of tons of ice pressing against the rock, the slopes were left too steep to support their own weight. In July 2025, just weeks before the event, glacial retreat exposed the very base of the slope that would soon fail. The icy straitjacket that kept the rocks from collapsing was no longer there. 研究人员在计算区域温度趋势时发现，自 1875 年左右以来，夏季气温上升了 1.1°C，导致雪线高度上升了约 169 米。当地冰层也明显变薄。仅在 2013 年至 2022 年间，支撑崩塌地点的冰川冰层就变薄了 100 到 130 米。失去了数百万吨冰层的挤压，斜坡变得过于陡峭，无法支撑自身重量。2025 年 7 月，即事件发生前几周，冰川退缩暴露了即将崩塌的斜坡底部。那件防止岩石崩塌的“冰制紧身衣”已不复存在。

Cracks in the rock

岩石中的裂缝

Retrospective analysis of optical and radar satellite imagery from the weeks preceding the slide showed no visible tension cracks or major deformational scarring on the slope. From the outside, it looked perfectly sound. But deep within the rock, surfaces were already grinding. Regional seismometers registered localized repeating earthquakes beginning as early as August 5. By August 9, these mini earthquakes were happening once every hour. In the six hours leading up to the main failure, the gaps between these seismic signals shrank to between 30 to 60 seconds. 对滑坡前几周的光学和雷达卫星图像进行回顾性分析显示，斜坡上没有可见的张力裂缝或主要的变形痕迹。从外表看，它看起来非常稳固。但在岩石深处，表面已经在相互摩擦。区域地震仪早在 8 月 5 日就开始记录到局部的重复地震。到 8 月 9 日，这些微型地震每小时发生一次。在主崩塌发生前的六个小时里，这些地震信号之间的间隔缩短到了 30 到 60 秒。

The cause of this uptick in microseismicity was the small patches of rock and ice snapping as a huge part of the cliff began to inch its way downward. About an hour before the landslide, the signals merged into a continuous, grinding slip. And then, the rock fell. The impact of 63.5 million cubic meters of rock hitting the fjord released forces large enough to be registered globally. The seismic waves that cascaded across the planet were recorded by sensor stations worldwide and were equivalent in energy to a magnitude 5.4 earthquake. 这种微震活动增加的原因是，随着悬崖的一大部分开始缓慢下滑，小块的岩石和冰层不断断裂。在山体滑坡发生前约一小时，信号合并为持续的摩擦滑动。随后，岩石坠落。6350 万立方米岩石撞击峡湾产生的力量大到足以被全球监测到。席卷全球的地震波被世界各地的传感器站记录下来，其能量相当于 5.4 级地震。

A close call

险象环生

During the summer, more than 20 boats navigate the Tracy and Endicott arms every day, including up to six large cruise ships. Had the landslide occurred a few hours later, in the middle of the tourist day, the outcome could have been tragic. But even at 5:26 in the morning, the tsunami was enough to terrify the few people present in the vicinity. 夏季期间，每天有超过 20 艘船只航行在特雷西峡湾和恩迪科特峡湾（Endicott Arm），其中包括多达 6 艘大型游轮。如果山体滑坡晚发生几个小时，正值旅游高峰期，后果可能会是悲剧性的。但即使是在清晨 5 点 26 分，这次海啸也足以让当时在附近的少数人感到恐惧。