Yantarni Volcano is an

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

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 the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

. It is on the

Alaska Peninsula The Alaska Peninsula (also called Aleut Peninsula or Aleutian Peninsula, ale, Alasxix̂; Sugpiaq: ''Aluuwiq'', ''Al'uwiq'') is a peninsula extending about to the southwest from the mainland of Alaska and ending in the Aleutian Islands. The ...

, in the

Aleutian Range The Aleutian Range is a major mountain range located in southwest Alaska. It extends from Chakachamna Lake (80 miles/130 km southwest of Anchorage) to Unimak Island, which is at the tip of the Alaska Peninsula. It includes all of the mountain ...

, between

Mount Aniakchak Mount Aniakchak (russian: Аниакчак) is a 3,700-year-old volcanic caldera approximately in diameter, located in the Aleutian Range of Alaska, United States. Although a stratovolcano by composition, the pre-existing mountain collapsed in ...

and

Mount Chiginagak Chiginagak Volcano is a stratovolcano on the Alaska Peninsula, located about 15 km NW of Chiginagak Bay. Eruptive history An unglaciated lava flow and an overlying pyroclastic-flow deposit extending east from the summit are the most recent ...

volcanoes. The volcano was not discovered until 1979 due to its remote location, lack of documented historic activity, and its rather modest summit elevation. The mountain was named after nearby Yantarni Bay, which in turn was named by Russian explorers after the abundance of yantar in the area.

Geology

The current cycle of eruptive activity began in middle

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

time with extrusion of andesitic

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

flows, perhaps from multiple vents. By the late Pleistocene, central-vent volcanism had initiated construction of a small stratovolcano.

800 BCE ± 500 years eruption

The cone was breached sometime in the late

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 ...

, between 2 and 3.5 ka, during the only Holocene event. The eruption was similar to that 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 ...

. and was followed by the emplacement of 1 cu km of

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...

s related to growth of the summit

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 ...

. It had a Volcanic Explosivity Index of 5

Notes

Sources

Volcanoes of the Alaska Peninsula and Aleutian Islands-Selected Photographs
Volcanoes of Lake and Peninsula Borough, Alaska Mountains of Lake and Peninsula Borough, Alaska Stratovolcanoes of the United States Mountains of Alaska Volcanoes of Alaska VEI-5 volcanoes Aleutian Range Pleistocene stratovolcanoes Holocene stratovolcanoes {{LakeAndPeninsulaAK-geo-stub