Bobrof Island

File:BobrofMap.png

{{Location map

|Alaska

|label=

|lat=52.105964

|long=-180.945335

|position=right

|width=300

|float=right

|caption=Location in Alaska

}}

{{Infobox mountain

| name = Bobrof Volcano

| photo = Bobrof Island and volcano.jpg

| photo_caption = Bobrof Island and the volcano

| elevation_ft = 2421

| elevation_ref = {{cite peakbagger |pid=29655 |name=Bobrof Volcano, Alaska |accessdate=2011-08-08}}

| prominence_ft =

| listing =

| location = North Pacific, part of Alaska

| range = Aleutian Islands

| map = Alaska

| map_caption = Alaska

| label_position = top

| coordinates = {{coord|51.9083333|N|177.4388889|W|type:mountain_region:US-AK_scale:100000_source:gnis|format=dms|display=inline,title}}

| range_coordinates =

| coordinates_ref = {{cite gnis |id=1893684 |name=Bobrof Volcano |accessdate=2011-08-08}}

| topo =

| type = Stratovolcano

| age = Holocene

| volcanic_arc = Aleutian Arc

| last_eruption =

| first_ascent =

| easiest_route =

}}

Bobrof Island ({{langx|ale|Walĝa}}{{cite book | first=K. | last=Bergsland | author-link=Knut Bergsland | year=1994 | title=Aleut Dictionary |publisher=Alaska Native Language Center |location=Fairbanks }}) is one of the Andreanof Islands subgroup of the Aleutian Islands in southwestern Alaska, United States.{{cite gvp|vn=311100|name=Bobrof|accessdate=July 10, 2009}} Bobrof Island is a small, uninhabited island about {{convert|9|mi|km}} north and west of Kanaga Island, and {{convert|7|mi|km}} northeast of Cape Sudak on Tanaga Island. Bobrof Island is {{convert|2.6|mi|km}} long and {{convert|1.8|mi|km}} wide with an area of {{convert|3|sqmi|km2}}, and consists primarily of the {{convert|2421|ft|m|adj=on}} high Bobrof Volcano. The volcanic crater, or cone, has been heavily dissected.{{cite web|url=http://www.avo.alaska.edu/pdfs/B1028E.pdf|title=Reconnaissance geology of some western Aleutian Islands, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin B 1028-E|publisher=United States Geological Survey|author=Robert R. Coats|author-link=Robert R. Coats|year=1956|access-date=July 10, 2009}} Underwater deposits adjacent to the island's northeast flank suggest an immense debris-avalanche has taken place.

Bobrof Volcano

Bobrof Volcano is an inactive stratovolcano which forms the small Bobrof Island. No recorded eruptions have taken place at Bobrof or in its vicinity. It has been considered as Holocene age.

= Geography and geology =

Because of the inclusion of Alaska, the United States has the largest number of active volcanoes in the world, many of them geologically young.{{cite web|url=http://pubs.usgs.gov/fs/2006/3142|title=The National Volcano Early Warning System (NVEWS): U.S. Geological Survey Fact Sheet FS 2006-3142|publisher=United States Geological Survey|author=Ewert, John |author2=Guffanti, Marianne |author3=Cervelli, Peter |author4=Quick, James|year=2006|access-date=July 9, 2009}} In Alaska, at least 50 volcanoes, including those in the Aleutian archipelago, have erupted in historical time.{{cite journal|url=http://www.dggs.dnr.state.ak.us/pubs/pubs?reqtype=citation&ID=16061|title=Alaska GeoSurvey News: NL 2008-1|publisher=Alaska Division of Geological & Geophysical Surveys|date=March 2008|access-date=July 9, 2009|volume=11|issue=1|pages=1–14}} Alaska accounts for about 80% of the United States' volcanoes, excluding the seamounts in the area, about 8% of the world's volcanoes, and most of these are located among the Aleutian Islands. The Aleutian Islands arc forms the northern boundary of the Pacific Ring of Fire, where tectonic activity generates earthquakes and volcanic eruptions regularly.

The volcano is thought to be of Holocene age. Though no historical eruptions have taken place at Bobrof, it has erupted at least once. This data can be confirmed through pyroclastic flow deposits containing andesite. Once these flows were studied, at a building intended for earthquake monitoring, they confirmed that Bobrof was prone to explosive activity.{{cite web|url=http://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Bobrof|title=Bobrof description and statistics|publisher=United States Geological Survey|work=Alaska Volcano Observatory|access-date=July 10, 2009}} There are lava deposits on the mountain which also suggest activity similar to shield eruptions. In collected samples, there are traces of basaltic andesite and dacite.{{cite web|url=http://www.avo.alaska.edu/pdfs/cit1997_5.0.pdf|author=Myers, J. D.|title=The geology, geochemistry and petrology of the recent magmatic phase of the central and western Aleutian Arc|publisher=University of Wyoming|year=1994|access-date=July 10, 2009}} No complete publications exist for Bobrof's definite geology, just those with facts and some information.