By ExploreNow Editor, on May 14th, 2012%
Volcano Type: Caldera
Volcano Status: Historical
Last Known Eruption: 1931
Summit Elevation: 1341 m 4,400 feet
Latitude: 56.88°N 56°53’0″N
Longitude: 158.17°W 158°10’0″W
One of the most dramatic calderas of the Aleutian arc, the 10-km-wide Aniakchak caldera was formed around 3400 years ago during a voluminous eruption in which pyroclastic flows traveled more than 50 km north to the Bering Sea and also reached the Pacific Ocean to the south. At least 40 explosive eruptions have been documented from Aniakchak during the past 10,000 years, making it the most active volcano of the eastern Aleutian arc. A dominantly andesitic pre-caldera volcano was constructed above basement Mesozoic and Tertiary sedimentary rocks that are exposed in the caldera walls to elevations of about 610 m. The ice-free caldera floor contains many pyroclastic cones, tuff cones, maars, and lava domes. Surprise Lake on the NE side drains through The Gates, a steep-walled breach on the east side of the 1-km-high caldera rim. Vent Mountain and Half Cone are two long-lived vents on the south-central and NW caldera floor, respectively. The first and only confirmed historical eruption took place in 1931 from vents on the west and SW caldera floor. Click Here For The Rest Of Aniakchak, Alaska
Originally posted 2010-08-25 03:51:13.
By ExploreNow Editor, on May 8th, 2012%
Volcano Type: Stratovolcano
Volcano Status: Radiocarbon
Last Known Eruption: 1900 BC ± 150 years
Summit Elevation: 1032 m 3,386 feet
Latitude: 56.552°N 56°33’9″N
Longitude: 158.785°W 158°47’5″W
 Black Peak The highly eroded stratovolcano and lava dome complex of Black Peak was constructed within an ice-free mid-Holocene caldera with two small caldera lakes on the northern and eastern sides. The pre-caldera volcano consists of andesitic-dacitic lava domes, lava flows, and volcaniclastic rocks that were constructed over a basement of Pliocene volcanogenic sedimentary rocks. Ash-flow tuffs and block-and-ash-flow deposits from the >10 cu km caldera-forming eruption, which occurred less than about 4000 years ago, fill the Ash Creek and Bluff Creek valleys to the west and north to depths of as much as 100 m. Most of the 3.5-km-wide caldera floor is occupied by a complex of nested dacitic lava domes and associated lava flows centered in the southern part of the caldera.
Click Here For The Rest Of Black Peak, Alaska, USA
Originally posted 2010-09-03 11:46:53.
By ExploreNow Editor, on May 2nd, 2012%
Volcano Type: Stratovolcano
Volcano Status: Historical
Last Known Eruption: 1995
Summit Elevation: 1307 m 4,288 feet
Latitude: 51.923°N 51°55’22″N
Longitude: 177.168°W 177°10’4″W
Symmetrical Kanaga stratovolcano is situated within the Kanaton caldera at the northern tip of Kanaga Island. The rim of Kanaton caldera forms a 760-m-high arcuate ridge south and east of Kanaga; a lake occupies part of the SE caldera floor. The volume of subaerial dacitic tuff is smaller than would typically be associated with caldera collapse, and deposits of a massive submarine debris avalanche associated with edifice collapse extend nearly 30 km to the NNW. Several fresh lava flows from historical or late prehistorical time descend the flanks of Kanaga, in some cases to the sea. Historical eruptions, most of which are poorly documented, have been recorded since 1763. Kanaga is also noted petrologically for ultramafic inclusions within an outcrop of alkaline basalt SW of the volcano. Fumarolic activity occurs in a circular, 200-m-wide, 60-m-deep summit crater and produces vapor plumes sometimes seen on clear days from Adak, 50 km to the east.
Click Here For The Rest Of Kanaga, Aleutian Islands, USA
Originally posted 2010-08-21 05:01:04.
By ExploreNow Editor, on April 8th, 2012%
Volcano Type: Stratovolcano
Volcano Status: Historical
Last Known Eruption: 1912
Summit Elevation: 2047 m 6,716 feet
Latitude: 58.280°N 58°16’47″N
Longitude: 154.963°W 154°57’48″W
Prior to 1912, Mount Katmai was a compound stratovolcano with four NE-SW-trending summits, most of which were truncated by caldera collapse in that year. Two or more large explosive eruptions took place from Mount Katmai during the late Pleistocene. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene in age, but Holocene lava flows from a flank vent descend the SE flank of the SW stratovolcano into the Katmai River canyon. Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km wide caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. The steep walled young caldera has a jagged rim that rises 500-1000 m above the caldera floor and contains a 250-m-deep, still-rising lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916. Post-1912 glaciers have formed on a bench within Katmai caldera.
 Katmai Caldera (Ivica Miskovic) Click Here For The Rest Of Katmai, Alaska
Originally posted 2010-09-01 04:46:02.
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