Amak Volcano is a

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Amer ...

stratovolcano in the

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large v ...

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. ...

, United States, from Anchorage. It is located on the eponymous island, from

Frosty Volcano Frosty Peak Volcano, also known as Mt. Frosty, Frosty Volcano, or Cold Bay Volcano, is a 6,299 ft (1,920 m) stratovolcano at the southwest end of the Alaska Peninsula in the U.S. state of Alaska. History Frosty Peak is the tallest ...

and near the edge of the

Alaskan 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 ...

's western flank. Only boats are allowed to access the island with a certain permit. Blocky (dotted with flat blocks of minerals and crystals) lava flows stream from its summit to its flanks. Three historical eruptions have taken place – two within the 18th century, the first from 1700–1710, and the latter in 1796. The earliest prehistoric eruption was believed to have taken place between 3050 and 2050 BCE.

Accessibility

Cold Bay Cold Bay ( ale, Udaamagax,; Sugpiaq: ''Pualu'') is a city in Aleutians East Borough, Alaska, United States. As of the 2010 census, the population was 108, but at the 2020 census this had reduced to 50. Cold Bay is one of the main commercial ...

, the city nearest Amak, is easily accessible by plane. Amak is accessible only by boat; airplanes are not permitted to land on the island. Private boat rides to Amak are available in Cold Bay, but for access to the Aleutian Islands, a permit is required from the

United States Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...

.Wood and Kienle, p. 51.

Geography and geology

Amak Island lies in the Bering Sea, north of the main

archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands. Examples of archipelagos include: the Indonesian Arc ...

of the Aleutians. It is one of two islands (along with Bogoslof Island) that are north of the main range. The United States has the most active volcanoes in the world, many of them geologically young. In Alaska, at least 50 volcanoes, including those in the Aleutian archipelago, have erupted in historical time. The state accounts for ~80% of the United States' volcanoes, excluding the seamounts in the area, ~8% of world volcanoes, and most of these are located among the Aleutian Islands. The Aleutian Islands arc serves as the northern boundary of the

Pacific Ring of Fire The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a region around much of the rim of the Pacific Ocean where many volcanic eruptions and earthquakes occur. The Ring o ...

, where tectonic activity generates earthquakes and volcanic eruptions in masses. The volcano is

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

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 predomin ...

in composition. It is a modest stratovolcano, rising no more than above sea level. The volcanic crater is distinct, and has erupted in historical times, only "blocky" lava flows. Charles Wood and Jürgen Kienle,

volcanologist A volcanologist, or volcano scientist, is a geologist who focuses on understanding the formation and eruptive activity of volcanoes. Volcanologists frequently visit volcanoes, sometimes active ones, to observe and monitor volcanic eruptions, col ...

s, propose that earlier activity, 4,000–5,000 years ago, consisted primarily of lavas of ethereal (fine) platy and thick andesite. Amak Volcano is unique in that its andesitic lavas, while composed the same as the other Aleutians, contain an abundance of

potash Potash () includes various mined and manufactured salts that contain potassium in water-soluble form.

. They also could contain more sodium carbonate and

rare-earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides ( yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

deposits than the Aleutian norm. Between Bogoslof, the other Aleutian island north of the main arc, and Amak, Amak's lavas are more alkalic and

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the grou ...

. Glaciation took place around the volcano roughly 6700 years BP, carving out U-shaped valleys. At the southwest flank of the island, a crater, likely a maar, can be found amid an alluvial plain.

Eruptive history

The Amak Volcano has erupted three times in historical times: circa 2550 B.C., from 1700–1710, and in 1796; the first of these events was identified with

tephrochronology 250px, Tephra horizons in south-central Iceland. The thick and light coloured layer at the height of the volcanologist's hands is rhyolitic tephra from Hekla. Tephrochronology is a Geochronology, geochronological technique that uses discrete l ...

. Each eruption has been characterized by lava flows, and the two most recent eruptions included a crater eruption.

References

Bibliography

External links

* {{Commons-inline, Amak Island, Amak Volcano Volcanoes of the Aleutian Islands Volcanoes of Aleutians East Borough, Alaska Volcanoes of Alaska Stratovolcanoes of the United States Holocene stratovolcanoes