Alaska faces a broad range of natural hazards due to its unique geography and geology. Its vast territory includes extreme cold climates, an exposed coastline, and a highly active tectonic boundary. Positioned along the Pacific Ring of Fire, the state is under constant geological stress. Its subarctic location subjects it to intense atmospheric and cryospheric forces, resulting in hazards ranging from sudden seismic events to long-term landscape changes.
Seismic and Volcanic Activity
Alaska’s southern margin sits atop the Alaska-Aleutian subduction zone, where the Pacific Plate is diving beneath the North American Plate. This process makes Alaska the most seismically active state in the country. The resulting friction generates enormous megathrust earthquakes, including the 1964 Magnitude 9.2 Good Friday event, the second largest recorded globally. On average, the region experiences one earthquake of Magnitude 8 or greater every 13 years and approximately six earthquakes between Magnitude 6 and 7 annually.
Intense seismic activity is the primary driver of tsunamis along the state’s rugged coastlines. Megathrust earthquakes cause the sudden vertical displacement of the seafloor, generating powerful, long-wavelength waves. While these tectonic tsunamis can travel across the Pacific, local tsunamis are also generated by seismically triggered submarine and subaerial landslides in steep bays and fjords. These landslide-generated waves pose an extreme threat because they can reach coastal communities within minutes, allowing almost no time for warning or evacuation.
Tectonic forces have also created the Aleutian Arc, a 1,500-mile chain that contains over 80 volcanoes, more than 50 of which have been active in recent history. The arc forms a significant part of the Pacific Ring of Fire, making Alaska home to three-quarters of all U.S. volcanoes that have erupted in the past two centuries.
The most common and widespread volcanic hazard is ash fall, which can be explosively blasted high into the atmosphere. This ash poses a significant threat to global aviation, as major international flight paths pass directly over the Aleutian Arc.
Volcanic ash is abrasive, can melt inside jet engines causing failure, and creates respiratory and mechanical hazards for downwind communities. Ash layers on the ground disrupt power systems, contaminate water supplies, and damage infrastructure like communication lines and runways. Large eruptions, such as the 1912 Novarupta event, blanketed areas with meters of ash and had regional effects. Even remote volcanoes can cause international air traffic disruptions due to the long-distance transport of ash clouds.
Extreme Weather and Wildfires
Alaska’s northern latitude and expansive interior subject it to severe atmospheric and hydrological events, distinct from geological hazards. One destructive form of flooding is the ice jam, which occurs during the spring thaw when river ice breaks up. The accumulating chunks of ice become lodged in narrow channels or bends of major rivers like the Yukon, creating a dam that rapidly backs up water.
This process leads to rapid water level rises, sometimes surging over 15 feet in a single night, inundating towns along the riverbanks. The subsequent release of the jam often sends floodwaters downstream, carrying massive chunks of ice that cause widespread structural damage. Coastal flooding is also a frequent hazard, particularly when strong autumn storms coincide with low sea ice, allowing large waves and storm surges to batter vulnerable shorelines. For example, the remnants of Typhoon Merbok in 2022 caused surges of three to seven feet along 1,000 miles of the western coast.
The warming climate is dramatically altering the state’s fire regime, leading to a substantial increase in the frequency and extent of wildfires. Warmer temperatures and earlier snowmelt are lengthening the fire season, which now runs from May through September. Since 2000, the total area burned has more than doubled compared to the previous two decades.
Most large fires occur in the interior’s boreal forest, or taiga, and are typically ignited by lightning strikes. These fires burn through vast areas, and the increased severity is accelerating the shift from coniferous spruce forests to deciduous trees like birch and aspen. Wildfires also present a health hazard, as the smoke can travel hundreds of miles, impacting air quality and respiratory health in distant communities.
Periglacial and Coastal Instability
Approximately 85% of Alaska’s land is underlain by permafrost, ground that remains frozen for at least two consecutive years. The stability of this frozen ground is compromised by rising air temperatures, leading to thaw subsidence or thermokarst. When ice-rich permafrost thaws, the resulting ground collapses or settles unevenly due to the massive volume loss from the melted ice.
This subsidence creates significant instability for human-built structures, causing buildings to sink, roads to warp, and runways to crack. The cost of repairing and mitigating damage to public infrastructure from permafrost thaw is projected to double by 2050. Many remote communities rely on this infrastructure, including roads and airfields, for their supply of food and medicine.
Coastal instability is compounded by the interaction of thawing permafrost and declining sea ice. Historically, sea ice formed a protective barrier against powerful storm waves and surges. With less ice cover and earlier melt-off, the open ocean has a longer fetch, the distance over which wind generates large waves. These larger waves strike coasts already weakened by thawing permafrost, making the frozen coastal bluffs more susceptible to collapse.
This combination of factors results in extreme erosion rates, sometimes exceeding 80 feet per year in some villages. Entire communities, such as Newtok, are being forced to relocate due to the rapid loss of habitable land. Landslides and avalanches are also a natural hazard, particularly in mountainous regions. Temperature fluctuations and heavy precipitation can destabilize steep, snow-covered or previously frozen terrain, leading to these events.