Mt. Amukta is an obscure name in a world dominated by volcanoes such as Mt. St. Helens, Kilauea, Mt. Pinatubo, Mt. Fuji and Nevada del Ruiz. But Mt. Amukta, a little-known, active volcano located in the Aleutian Island chain, was created by the same tectonic forces that formed its more famous brethren in the Pacific Ocean "Ring of Fire. "
Mt. Amukta
One of 40 active volcanoes in Alaska, 3,497-foot-tall Mt. Amukta overlies an ancient shield volcano and dominates the tiny Aleutian Island of Amukta. The Aleutian Islands are a volcanic island arc extending more than 1,000 miles into the Pacific Ocean and Bering Sea. The eruptive history of Mt. Amukta is unclear. The first historical records of Alaskan volcanoes were written by Russian sailors and fur traders beginning in the 1760s. Many of the early records are incomplete and possibly inaccurate. The last known eruption of Mt. Amukta was a minor event in 1997.
Plate Tectonics and Subduction
Earth's hard outer layer, called the lithosphere, is broken into about 12 large pieces and several smaller pieces called lithospheric plates, that move slowly on a semi-solid layer of the mantle. Most volcanoes form as a result of this motion, known as plate tectonics. Mt. Amukta and the rest of the Aleutian Island chain were formed as the result of a tectonic process called subduction zone volcanism.
Subduction occurs when the boundaries of two lithospheric plates converge and one dives, or descends, below the other. This is called a subduction zone. When an oceanic crust bends and subducts beneath adjacent oceanic crust it creates an oceanic trench. Oceanic trenches such as the Mariana Trench, Philippine Trench, Aleutian Trench and Japan Trench are among the deepest points in the ocean. The subduction process also often leads to volcanism.
Formation of The Aleutian Trench and Volcanic Island Arc
The Aleutian Trench and volcanic island arc, including Mt. Amukta, were formed at a convergent plate boundary, or subduction zone, where the Pacific Plate descends beneath the North American Plate. Heat and pressure combined to partially melt the lithospheric rock as it descended through the Aleutian trench into the mantle. The partially melted rock, called magma, rose to the surface to form a volcanic island arc adjacent to the trench. This island arc, which stretches more than 1,000 miles along the southern edge of the Bering Sea, is called the Aleutian Islands. The total length of the Aleutian Trench is approximately 2,100 miles, extending from the Kamchatka Trench to the Gulf of Alaska.
The Pacific "Ring of Fire"
Mt. Amukta and the \Aleutian Island arc are part of the most active area of volcanic activity on Earth: the "Ring of Fire." This is a region of subduction zone volcanism at the margins of the Pacific Ocean encompassing the Cascades range and Aleutian Islands in North America, Japan, the volcanic islands of the South and Western Pacific and the Andes of South America. Nearly all subduction zone volcanoes are composite, or stratovolcanoes, which tend to erupt explosively, producing deadly pyroclastic flows and spewing ash miles into the atmosphere. The Ring of Fire has produced some of the most famous and destructive volcanic eruptions in history, including Krakatoa, Tambora, Mt. St. Helens and Mt. Pinatubo. This belt of subduction zone volcanoes, including Mt. Amukta, remain under the intense the scrutiny of the geoscientific community.
Tags: subduction zone, Aleutian Island, Ring Fire, Aleutian Islands, Aleutian Trench, Pacific Ocean