Segula Volcano lies westward 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 ...

on the

Segula Island Segula Island ( ale, Chiĝulax̂) is an island in the Rat Islands archipelago of the western Aleutian Islands, Alaska. It consists of a Holocene stratovolcano, called Segula Volcano. Segula Island is three to four miles in diameter, and is loca ...

in the

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi language, Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a cha ...

of Alaska. An inactive

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 ...

, it has not produced any historical eruptions, while barely eroded deposits on the flanks suggest that activity took place at the volcano as late as a couple of hundred years ago. Built on top of a shallow platform, the volcano grew steadily from eruptions, and is composed of

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

of flow deposits and

pyroclastic Pyroclastic rocks (derived from the el, πῦρ, links=no, meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroc ...

material.

Geography and geology

Part of the

Rat Islands The Rat Islands ( ale, Qax̂um tanangis, russian: Крысьи острова) are a group of American High islands, volcanic islands in the Aleutian Islands in southwestern Alaska, between Buldir Island and the Near Islands group to its west, ...

, Segula Volcano is located, along with the other Aleutians, in the Pacific Ocean. It is located in a row of islands which stretch from

Kiska Island Kiska ( ale, Qisxa, russian: Кыска) is one of the Rat Islands, a group of the Aleutian Islands of Alaska. It is about long and varies in width from . It is part of Aleutian Islands Wilderness and as such, special permission is required ...

to as far east as the Andreanof Islands.

and the volcano formed over an underwater land surface which hosts other Aleutian volcanoes such as Khvostof and Davidof. Andesitic lava and pyroclastic material was ejected from the underwater crater, building up over time to break the surface from nearly underwater. Segula is made up of overlapping strata of lava flows and pyroclastic deposits, built up from the caldera. Largely built of eruptive material, the stratovolcano is conical and marked by a fissure. Since it is surrounded by lava flows on the north flank and a

cinder cone A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...

on the other, the mountain's caldera, or main crater, appears tiny and is therefore very difficult to make out from any photographs. The north side of the island is summarized by sharp

cliffs In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on co ...

and a shallow reef which together make accessibility from that side difficult. It has not had a recorded eruption, though numerous deposits of lava flows and other

ejecta Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials (tephra) that came out of a volcanic explosion and magma ...

on the southern and eastern flanks and a submarine deposit to the north of the summit which extends for have very little erosion, making it likely that Segula has erupted in the last few hundred years.

References

{{coord, 52, 00, 55, N, 178, 08, 12, E, display=title Volcanoes of the Aleutian Islands Landforms of Aleutians West Census Area, Alaska Stratovolcanoes of the United States Volcanoes of Alaska Volcanoes of Unorganized Borough, Alaska Cinder cones of the United States