Semisopochnoi Island
Encyclopedia
Semisopochnoi Island ( "having seven hills"; ) is part of the Rat Islands
group in the western Aleutian Islands of Alaska
. The island is uninhabited and provides an important nesting area for maritime birds. The island is of volcanic origin, containing several volcanoes including Mount Cerberus. It has a land area of 85.558 square miles (221.6 km²).
At 179°37' East, the easternmost tip of Semisopochnoi is the easternmost land location in the United States, and is arguably the easternmost location in North America
. Semisopochnoi sits only 23 minutes west of the 180th meridian
and therefore is in the Eastern Hemisphere
.
The large Least and Crested Auklet colony near Sugarloaf Head is one of the largest among the nine auklet colonies in the Aleutian Islands. Crested Auklets and Least Auklets breed in one colony, located on the south facing slopes of Sugarloaf Peak volcano and its associated cinder cones near Sugarloaf Head. Semisopochnoi Island also supports a significant population of Red-faced Cormorants.
In total, Semisopochnoi supports well over a million seabirds, most of which are Least Auklets or Crested Auklets.
Semisophochoi's last known volcanic eruption was in April 1987. An historic eruption of Semisopochnoi was reported in 1873, and at least four others may have occurred in the previous hundred years, but documentation is scanty. These eruptions apparently emanated from the flanks of Mount Cerberus; the most recent flow appears to be less than a century old.
at 12°08' West and Cape Spear
, Newfoundland, Canada
at 52°37' West. Cape Spear
appears to be the easternmost location on a political map of North America if one ignores the 180th meridian
. Unlike Semisopochnoi Island, Cape Spear
is close to a community; that being Blackhead, an amalgamated area of the City of St. John's
, about 3 kilometres (2 mi) away. For these and other reasons, Cape Spear
is traditionally considered to be the easternmost location in North America. The locations within the territory of the Aleutian Islands which lie exactly on the 180th meridian are simultaneously the most westerly and most easterly points of the USA. Those locations are all in the sea.
Rat Islands
The Rat Islands are a volcanic group of islands in the Aleutian Islands in southwest Alaska, between Buldir Island and the Near Islands group to its west, and Amchitka Pass and the Andreanof Islands group to its east, at about ....
group in the western Aleutian Islands of Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. The island is uninhabited and provides an important nesting area for maritime birds. The island is of volcanic origin, containing several volcanoes including Mount Cerberus. It has a land area of 85.558 square miles (221.6 km²).
At 179°37' East, the easternmost tip of Semisopochnoi is the easternmost land location in the United States, and is arguably the easternmost location in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Semisopochnoi sits only 23 minutes west of the 180th meridian
180th meridian
The 180th meridian or antimeridian is the meridian which is 180° east or west of the Prime Meridian passing through the Royal Observatory, Greenwich. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it for the most part passes...
and therefore is in the Eastern Hemisphere
Eastern Hemisphere
The Eastern Hemisphere, also Eastern hemisphere or eastern hemisphere, is a geographical term for the half of the Earth that is east of the Prime Meridian and west of 180° longitude. It is also used to refer to Europe, Asia, Africa, and Australasia, vis-à-vis the Western Hemisphere, which includes...
.
Wildlife
Semisopochnoi has no native land mammals. Arctic foxes were introduced to the island during the 19th century for fur farming and removed in 1997. Most ground-nesting bird species (Aleutian Cackling Goose, Rock Ptarmigan) and most burrow-nesting seabirds (storm-petrels, Ancient Murrelets, Cassin's Auklets, Tufted Puffins) were extirpated by foxes; Semisopochnoi Island is currently in the early stages of recovery. The island has remained free of Norway rats.The large Least and Crested Auklet colony near Sugarloaf Head is one of the largest among the nine auklet colonies in the Aleutian Islands. Crested Auklets and Least Auklets breed in one colony, located on the south facing slopes of Sugarloaf Peak volcano and its associated cinder cones near Sugarloaf Head. Semisopochnoi Island also supports a significant population of Red-faced Cormorants.
In total, Semisopochnoi supports well over a million seabirds, most of which are Least Auklets or Crested Auklets.
Geology
Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains a caldera 8 km wide. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1,221 meter Anvil Peak, a double-peaked cone that forms much of the island's northern part. The three-peaked, 774-meter high Mount Cerberus is a volcano within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855 m high Sugarloaf Peak south-southeast of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the northeast part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.Semisophochoi's last known volcanic eruption was in April 1987. An historic eruption of Semisopochnoi was reported in 1873, and at least four others may have occurred in the previous hundred years, but documentation is scanty. These eruptions apparently emanated from the flanks of Mount Cerberus; the most recent flow appears to be less than a century old.
Easternmost North America location debate
The other contenders for the title of easternmost North America location are Nordost Rundingen, GreenlandGreenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
at 12°08' West and Cape Spear
Cape Spear
Cape Spear, located on the Avalon Peninsula near St. John's, Newfoundland, is the easternmost point in North America , excluding Greenland and the portions of Alaska west of the 180th parallel of longitude . Cape Spear is close to Blackhead, an amalgamated area of the City of St. John's, about...
, Newfoundland, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
at 52°37' West. Cape Spear
Cape Spear
Cape Spear, located on the Avalon Peninsula near St. John's, Newfoundland, is the easternmost point in North America , excluding Greenland and the portions of Alaska west of the 180th parallel of longitude . Cape Spear is close to Blackhead, an amalgamated area of the City of St. John's, about...
appears to be the easternmost location on a political map of North America if one ignores the 180th meridian
180th meridian
The 180th meridian or antimeridian is the meridian which is 180° east or west of the Prime Meridian passing through the Royal Observatory, Greenwich. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it for the most part passes...
. Unlike Semisopochnoi Island, Cape Spear
Cape Spear
Cape Spear, located on the Avalon Peninsula near St. John's, Newfoundland, is the easternmost point in North America , excluding Greenland and the portions of Alaska west of the 180th parallel of longitude . Cape Spear is close to Blackhead, an amalgamated area of the City of St. John's, about...
is close to a community; that being Blackhead, an amalgamated area of the City of St. John's
St. John's, Newfoundland and Labrador
St. John's is the capital and largest city in Newfoundland and Labrador, and is the oldest English-founded city in North America. It is located on the eastern tip of the Avalon Peninsula on the island of Newfoundland. With a population of 192,326 as of July 1, 2010, the St...
, about 3 kilometres (2 mi) away. For these and other reasons, Cape Spear
Cape Spear
Cape Spear, located on the Avalon Peninsula near St. John's, Newfoundland, is the easternmost point in North America , excluding Greenland and the portions of Alaska west of the 180th parallel of longitude . Cape Spear is close to Blackhead, an amalgamated area of the City of St. John's, about...
is traditionally considered to be the easternmost location in North America. The locations within the territory of the Aleutian Islands which lie exactly on the 180th meridian are simultaneously the most westerly and most easterly points of the USA. Those locations are all in the sea.
External links
- Semisopochnoi Photos Photographs from Semisopochnoi Island, July 2008