Description

General physical description:

Hayes Volcano (not to be confused with Mount Hayes, a prominent nonvolcanic peak in the Alaska Range) is quite unusual among Aleutian Arc volcanoes because it doesn’t have a defined cone shape or even a proper summit ^[1] . In fact, it wasn’t recognized as a volcano until 1975 ^[2] . Hayes is easy to miss among the other peaks of the surrounding Tordrillo Mountains, and 90% of its nondescript edifice is buried under glacial ice and perennial snow. What does stick up through the snow and ice cover is made up of deeply eroded lava dome, dome debris, and pyroclastic flow deposits ^[1] . Little is known about this volcano, which is extremely remote and rarely visited, but it has the potential to severely disrupt the largest population center in Alaska should it erupt.

Location:

Hayes Volcano is the eastern and northernmost volcano in the Aleutian Arc. It is located towards the northern end of the Tordrillo Mountains, which are south of the Alaska Range and to the northwest of Cook Inlet. Hayes is found along a ridge just northeast of the higher nonvolcanic peak of Mount Gerdine at the head of the Hayes Glacier, which gives the volcano its name ^[3] . Hayes Volcano is located 141 km WNW of Anchorage, and the closest community to the volcano is Skwentna, 76 km away. Hayes is 90 km north of Mount Spurr, the next volcano in the Aleutian Arc, which is also in the Tordrillo Mountains ^[1] .

Notable eruptions:

Hayes Volcano has not erupted in historical times and has never been noted to exhibit signs of unrest by the Alaska Volcano Observatory ^[1] . However, volcanic ash found across interior, south-central, and southeast Alaska has been tied to prehistoric eruptions of Hayes Volcano. The most recent major eruptive period, dated to approximately 1850-1550 BCE (3500-3800 cal yBP) ^[4] , included several large Plinian eruptions. During this time, an eruption deposited at least 2 cm of ash at Anchorage’s present location, and 1 cm at Homer and Kenai. Numerous thick pyroclastic flow and lahar deposits dating from this period have also been identified in the Hayes River and Skwentna River drainages ^[1] .

Another set of deposits at Hayes River have been dated to before the above eruptive period, indicating at least two older eruptions of Hayes Volcano: one tephra layer dated to approximately 2500 BCE (4450 cal yBP), and an older ignimbrite ^[4] . There is also some evidence for one more recent eruption of Hayes Volcano sometime between 50 and 1500 CE ^[5] .

Special hazard info:

Hayes Volcano is listed as “high threat” by the most recent edition of the USGS National Volcanic Threat Assessment ^[6] . While Hayes Volcano has not erupted in historical times, some of its prehistoric eruptions have been very large. Ash from a similar major eruption in the future would likely grind air traffic at busy Ted Stevens International Airport to a halt, cut off air access to interior Alaska, pose a public health and environmental threat to the surrounding communities, including Anchorage, and affect oil and gas, shipping activities, and power generation in Cook Inlet ^[1] . Additionally, because Hayes Volcano is covered in a huge volume of ice and snow, future eruptions are very likely to generate lahars, which could reach the mouth of the Skwentna River near the community of Skwentna ^[1] .