Hayes Volcano is a

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

in southwestern Matanuska-Susitna Borough, Alaska, 135 km northwest of

Anchorage Anchorage, officially the Municipality of Anchorage, is the most populous city in the U.S. state of Alaska. With a population of 291,247 at the 2020 census, it contains nearly 40 percent of the state's population. The Anchorage metropolita ...

, that was not discovered until 1975. It is responsible for a series of six major

tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...

layers in the Cook Inlet region of Alaska. Hayes was mostly destroyed by at least six catastrophic eruptions between 3,400 and 3,800 years ago, and the average volume of these eruptions was 2.4 cubic km. In comparison, the volume of the May 18, 1980 eruption of Mount St. Helens was about 1 cubic km. The eruptions of Hayes Volcano during that time were the most voluminous

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

eruptions to have occurred in the Cook Inlet region. There is currently no fumarolic activity present. The last eruption of Hayes Volcano occurred roughly 1,200 years ago. It is named after the adjacent Hayes Glacier.

Physical setting

Hayes Volcano is an ice-shrouded, glacially scoured eruptive center of

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

age composed of pyroclastic deposits, volcanic breccia, and lava domes. Although the edifice of the volcano is largely covered by glacier ice, parts of small lava domes, dome debris, and pyroclastic deposits project through the ice at altitudes of 2,400 to 2,800 meters above sea level. The volcano is nestled within the Tordrillo Mountains, a rugged, glacier-clad mountain range, between the

Alaska Range The Alaska Range is a relatively narrow, mountain range in the Southcentral Alaska, southcentral region of the U.S. state of Alaska, from Lake Clark at its southwest endSources differ as to the exact delineation of the Alaska Range. ThBoard on G ...

and Cook Inlet, that is composed primarily of older plutonic

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

s. Most of the area is in high relief (greater than 1,500 meters) and supports an extensive complex of glacier ice that covers most of the mountainous terrain. The volume of perennial snow and glacier ice on Hayes Volcano is not known but is comparable to the ice volume present on Mount Spurr volcano (to the south), which supports about 67 km³ of ice and perennial snow. Unlike the other volcanoes in the Cook Inlet area, Hayes Volcano lacks a well-defined cone, and deposits from eruptions older than the 4,400-to-3,600-year-old eruption are not known. The volcano is unusual in this regard because all other volcanoes in the Cook Inlet area consist of relatively voluminous assemblages of volcanic rock and debris that formed over many tens of thousands of years.

Historical eruptions

Historical eruptions of Hayes Volcano are not known and evidence of recent eruptive activity is not apparent on the volcano. During trips to the volcano in 1999 and 2000, signs of volcanic unrest, such as melting of glacier ice, steaming, or discoloration of the ice surface by volcanic ash were not observed.

References

{{DEFAULTSORT:Hayes Volcano Active volcanoes Volcanoes of Matanuska-Susitna Borough, Alaska Mountains of Matanuska-Susitna Borough, Alaska Two-thousanders of the United States Stratovolcanoes of Alaska VEI-5 volcanoes Holocene stratovolcanoes