Why Tsunamis Happen in Alaska
Any large movement of land that causes major displacement of ocean water—from earthquakes, landslides, or volcanic eruptions—can generate a tsunami. Tsunamis generated in Alaska have caused damage and loss of life across the Pacific Ocean.
Local tsunamis are “near-field” hazards for which people may have only a few minutes to reach safety.
A tsunami can be a series of waves that may last for hours, and the first wave may not be the largest.
Animation of how tsunamis are generated along subduction zones
A tectonic tsunami is caused by an earthquake that shifts the ocean bottom, which displaces water. Earthquakes frequently rumble coastal Alaska. The Alaska–Aleutian megathrust, a subduction zone that lies just offshore where the Pacific Ocean plate scrapes under the continental plate of mainland Alaska, creates some of the world’s largest earthquakes.
Rocks, earth, and debris released during a landslide displace water, creating a tsunami. Some of the largest tsunamis in history originated from a landslide. A landslide may release spontaneously or be triggered by an earthquake.
Many places along Alaska’s rugged coast are poised for landslides above or below the ocean’s surface.
Volcanic eruptions that displace water could generate a tsunami. A recent example of this is the January 15, 2022 eruption of the underwater volcano Hunga Tonga in the southwest Pacific, which generated a damaging tsunami. This tsunami reached Alaska, creating waves of about three feet in King Cove. Another example is the 1883 eruption of Augustine Volcano in Alaska. The north side of the peak collapsed, generating a tsunami.
Distant vs. local tsunamis
A tsunami is considered distant if it takes more than three hours to reach the observer. Distant tsunamis triggered by earthquake or volcanic activity around the Pacific Rim can reach Alaska. Their arrival time is typically within a few hours of their origin, but depends on where they originated and how fast they are moving.
Animation of how tsunamis are generated by underwater landslides
Local tsunamis may reach the shore minutes after the landslide or first earthquake shaking that triggers them. Local tsunamis caused by an earthquake along the Alaska–Aleutian megathrust, such as in the Gulf of Alaska or offshore of Kodiak Island, are extremely dangerous because the first wave can arrive so quickly that there is little time for warnings or evacuation.
Tsunamis caused by submarine (below water) and subaerial (above the water) landslides are a serious hazard in bays and fjords of coastal Alaska, particularly in Southeast and Southcentral Alaska. This region has a long history of tsunami waves generated by submarine and subaerial landslides, avalanches, and rockfalls. These have produced some of the largest tsunami waves recorded and, unlike earthquake-induced tsunamis, they can strike with no warning.
The tsunami travel time maps for various historical events can be accessed here.
Learn more about Alaska’s largest landslide-triggered tsunamis through a multimedia, interactive StoryMap.
Historical Tsunamis
Alaskan history is filled with stories of tsunamis that have caused devastating damage. In addition to those described in this multimedia, interactive StoryMap, the following are accounts of some of Alaska’s largest tsunamis. (Note: Run-up is the elevation above sea level that a tsunami wave reaches.)
1883 Augustine Volcano tsunami
Augustine Volcano in Cook Inlet erupted in 1883, causing the flank of the volcano to collapse into the bay. The resulting tsunami reached the opposite side of Cook Inlet, then rebounded back to Augustine Island. An eyewitness account from a trading post about 50 miles away mentioned four wave arrivals. The sea rise was 20 feet above the usual level near Nanwalek (called English Bay at the time). In the nearby village of Port Graham, the waves flooded homes and pushed boats onto shore. Possible casualties were five or six Aleuts in a hunting party reportedly on Augustine Island before the eruption. The timing of the landslide during low tide helped lessen damage in the surrounding communities (in this region, sea level can change almost 15 feet between low and high tides).
1958 Lituya Bay megatsunami
Landslides in Lituya Bay in Southeast Alaska following a magnitude 7.8 earthquake on the Fairweather Fault produced a megatsunami with 1,720 feet of run-up.
Learn more about this event here.
1964 Great Alaskan Earthquake
Propagation of the tsunami wave produced by the 1964 M9.2 earthquake. Red shows the highest wave heights recorded with heights decreasing down to blue.
On March 27, a magnitude 9.2 earthquake, the second-largest ever recorded, shook Alaska for nearly five minutes. Originating in Prince William Sound along the subduction zone, the earthquake caused both local and tectonic tsunamis. More than 20 local landslides (both above and below the ocean) generated waves that arrived within minutes in nearby communities, leaving no time for warning or evacuation. Whittier, Seward, and Valdez were struck by waves before shaking had even finished. These local tsunamis accounted for at least 82 of the 122 tsunami-related fatalities. In Valdez Arm, the locally-induced tsunami waves were reported to reach a maximum height of 170 feet (52 meters). Waves from the more distant earthquake-generated tsunami followed, continuing for several hours afterward.
2015 Icy Bay tsunami
The giant wave of Icy Bay, with a run-up of 600 feet, was caused by the collapse of a mountainside near Tyndall Glacier into Taan Fjord after a period of heavy rains. You can read more in Landslide tsunamis: why they're different and how to prepare and Lessons for Alaska from the Palu Tsunami.
2025 Tracy Arm Landslide tsunami
Early on August 10, 2025 the Earthquake Center received reports from people out boating of a mysterious local tsunami in the Tracy Arm fjord area of Southeast Alaska. Seismic data indicated a landslide, so Earthquake Center staff applied our landslide detection system to quickly estimate an initial size and location. As results filtered in over the next days and weeks, this landslide tsunami turned out to be the second largest ever recorded, with runup across from the landslide reaching 1,600 feet. Learn more about the Tracy Arm Landslide in this interactive StoryMap or Significant Event profile.