Ash FlowA turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure
CalderaA large crater formed by collapse or subsidence of the ground surface following a great eruption
Lava DomeA steep-sided mass of viscous and commonly blocky lava extruded from a vent; typically has a rounded top and roughly circular outline
Ring of FireThe regions of mountain-building earthquakes and volcanoes which surround the Pacific Ocean
Volcanic Activity in Alaska's National Parks
Volcanic activity is evident in locations throughout Alaska, including several national parks and preserves. Some volcanoes, such as Illiamna and Redoubt in Lake Clark National Park, are under close watch by scientists. Others, such as Wrangell Mountain in Wrangell-St. Elias National Park and Preserve, show active vents reminding us of their potential activity. Some parks, such as Bering Land Bridge National Preserve and Sitka National Historical Park, show evidence of past volcanic activity in land features and soil. See the actvity levels for all active volcanoes in Alaska, or learn more about a particular park by choosing from the menu below.
100th Anniversary: Novarupta eruption of 1912
"Put away as much water as you can and store it, reserve it.... Turn your boots upside down. They will be filled up with ash.' Increasingly severe earthquakes in the days preceding the June 6th  eruption led to the complete abandonment of the native villages in the Katmai region." (From Witness: Firsthand Accounts of the Largest Volcanic Eruption in the Twentieth Century)
Graphic: USGS, download larger file size
Volcanoes and People
Volcanoes, while simultaneously fascinating and terrifying, are an integral part of the Alaskan landscape. People have shared the landscape with volcanoes through time and across the globe. We have learned to adapt to the dramatic changes that volcanoes cause– including recovering from short term devastation to exploiting long–term ecological benefits. For example, volcanic eruptions and resulting ash can help form fertile soil that benefits entire ecosystems, attracting plants and animals that people rely on to survive– or wipe them all out in an instant.
Volcanoes play an extremely important role in the prehistory and history of Alaska. Archaeological research and oral history has shown that volcanoes can severely stress or destroy human settlements and trade networks and divide populations, perhaps for centuries. Volcanoes can cause animals, such as caribou, to alter migration routes or completely abandon entire areas. Conversely, volcanoes can preserve archaeological materials and teach us how ecosystems respond to volcanic eruptions and provide clues to how people adapt to volcanic landscapes. Many archaeological sites throughout Alaska have multiple layers of volcanic ash– demonstrating that volcanic activity played a significant role in how humans adapted to a variety of environments, dictated where they lived, hunted, and how they traveled across the landscape. In the past, people relied on volcanic material such as obsidian to make tools for hunting and processing food, and traded it across vast distances. Geothermal features, such as hot springs, have also attracted people and wildlife for millennia. The archaeological record demonstrates that people frequently returned after an eruption, and can tell us how long it took, re–emphasizing the fact that the ecological advantages frequently outweigh the risks. The resilient Alaskan people continue to adapt and thrive in this volatile and dynamic environment.