Hayes Volcano is a

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

in southwestern

Matanuska-Susitna Borough, Alaska Matanuska-Susitna Borough (often referred to as the Mat-Su Borough) is a borough located in the U.S. state of Alaska. Its county seat is Palmer, and the largest community is the census-designated place of Knik-Fairview. The borough is part of ...

, 135 km northwest of

Anchorage Anchorage () is the largest city in the U.S. state of Alaska by population. With a population of 291,247 in 2020, it contains nearly 40% of the state's population. The Anchorage metropolitan area, which includes Anchorage and the neighboring Ma ...

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

tephra Tephra is fragmental material produced by a 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, they rem ...

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 Mount St. Helens (known as Lawetlat'la to the indigenous Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United St ...

was about 1 cubic km. The eruptions of Hayes Volcano during that time were the most voluminous

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

eruptions to have occurred in the Cook Inlet region. There is currently no

fumarolic A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

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). It follows the Neogene Period and spans from 2.58 million years ...

age composed of pyroclastic deposits, volcanic

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

, and

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...

s. 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, 600-mile-long (950 km) mountain range in the 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. ThBoar ...

and Cook Inlet, that is composed primarily of older

plutonic Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March ...

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock ...

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 Mount Spurr ( Dena'ina: ''K'idazq'eni'') is a stratovolcano in the Aleutian Arc of Alaska, named after United States Geological Survey geologist and explorer Josiah Edward Spurr, who led an expedition to the area in 1898. The Alaska Volcano Obse ...

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 Mountains of Alaska Stratovolcanoes of the United States VEI-5 volcanoes Volcanoes of Alaska Holocene stratovolcanoes