Cook-Inlet Geological Hazards

Mayday.... Mayday.... We have lost all power to all 4 engines due to flying in a volcanic ash plume and are gliding to the ground. The South central region in Alaska is impacted by a subducting tectonic plate which has created many volcanoes and geographical features. The location is home to the majority of state residents who are vulnerable to these dangers. Volcanic eruptions and earthquakes are major geological threats that continue to be a hazard in the Cook Inlet South Central Region of Alaska.

South central Alaska is a very geologically active area because it is underneath a major subduction zone. In a subduction zone a plate descends towards the core of the earth and becomes molten magma which eventually makes its way to the surface due to a decrease in density. As the magma rises upwards it creates enormous pressure which occasionally causes a volcanic eruption. The explosion brings forth ash and lava which accumulates to form volcanoes. The zone is comprised of the Pacific plate which is subducting underneath the North American Plate.

The Cook Inlet volcanoes are located on the eastern Aleutian volcanic arc and are 200 miles away from the subduction zone. The volcanoes in the region have developed because of the Pacific plate traveling a long distance underneath the North American plate before it melts. The area has well over six large stratovolcanoes which are the most destructive and dangerous among volcanic classifications. These historically active volcanoes are Iliama, Redoubt, Spurr, and Augustine, all of which have produced catastrophic eruptions in the past. Hayes was recently active within the Holocene period and the Double Glacier volcano is inactive. The last explosive volcanic activity occurred; Iliama in 1953, Redoubt in 2009, Spurr in 1992, and Augustine in 2005. (Noa) The four active volcanoes continue to be a threat to the region because of continuous eruptions. For example, Redoubt also exploded earlier in 1989 spewing ash over 45,000 ft. high into the atmosphere. The dome collapsed sending lahars and mudflows towards the Cook Inlet area which luckily did not damage any of the populated areas. The explosion almost took out a 747 airplane that went through an ash plume and lost power to all four engines. Fortunately after dwindling towards the surface with no power for several minutes their engines restarted and landed safely in Anchorage. From a recent preliminary report from the U.S. Geological Survey, there is major concern over the volcano Redoubt. The volcano is located only a few hundred kilometers of the majority of the population in Alaska and has erupted explosively six times since 1778. The eruption in 1989 emitted substantial volumes of volcanic ash to altitudes greater than 45,000 ft. above sea level and created pervasive flooding in the Drift River valley. The fallout of volcanic ash had forced school and business operations to close and caused economic hardship. Many individuals had encountered respiratory problems from breathing in ash and its volcanic particles. Pyroclastic flows have come out of the volcano rapidly traveling down the slopes destroying everything in its path. With studies done from the eruption in 1989 the U.S. Geological Survey has indicated that more eruptions will come forth and there is a good indicator the next eruption could be worse. The department has required the public to become aware of future eruptions and to plan accordingly so that risks such as loss of life and property are minimized as much as possible.

Earthquakes are commonly associated with the volcanoes in the region. Earthquakes are produced as tectonic plates interact with one another and occur along preexisting faults. (Geology Book) Alaska has ten very active faults which cause most of the 24,000 annual earthquakes. Alaska is also the most seismically active state and accounts for 52% of all trembles in the United States as well as 11% worldwide. According to the US Geological survey there