Alaska Science Center
ABOUT THE ALASKA
Alaska is one of the most geologically active areas in the world. The surface of the earth has numerous large plates (sections of the earth's crust that move about the surface) crashing into each other, grinding past each other, and overrunning one another. Alaska is home to one of the most active plate boundaries on the planet, where the Pacific Plate is being forced under (or subducting under) the North American Plate at rates greater than 7 cm/year (just under 3 inches/year).
Though this process forms much of the magnificent mountain ranges and peaks in Alaska, the process also brings to Alaska earthquakes and volcanoes. Alaska is the most seismically active state in the U.S. by a large margin and one of the most active areas in the world. Three of the six largest earthquakes ever recorded world-wide occurred in Alaska as did seven of the 10 largest in the U.S.
Similarly, the plate movements produce one of the most active volcanic arcs in the world. Roughly 10% of the worlds active volcanoes are in Alaska and, on average, 1-2 erupt each year. The largest eruption in the 20th century was at Katmai on the Alaska Peninsula in 1912. Though many of Alaska's volcanoes are in the remote Aleutians, volcanic ash resulting from eruptions of any of these volcanoes pose a significant hazard to the aviation industry, including the wide-body jets flying the North Pacific air routes between North America and Asia.
Congress authorized the U.S. Geological Survey to issue warnings of geologic-related hazards, including earthquakes and volcanoes (Public Law 93-288, Federal Register vol. 42, No 70, page 19292, April 12, 1977). Through formal partnerships such as the Alaska Volcano Observatory and the Alaska Earthquake Information Center, work by the partners agencies are presented to the public as a common voice.