The USGS continues to closely monitor volcanoes around the United States, with four now at Orange / Watch elevated due to noted activity on all four of them. The Great Sitkin, Pavlof, Semisopochnoi and Kilauea are the four volcanoes showing signs of trouble.
With the exception of Hawaii’s Mauna Loa, which remains yellow / advisory, all of the other volcanoes that the USGS closely monitors are Green or not rated.
The USGS tracks about 169 volcanoes that could become active in the United States, the majority in Alaska.
Alaska is home to many volcanoes, although there are over 130 volcanoes and volcanic fields that have remained active over the past 2 million geologically young years. Since the mid-1700s, 50 have remained active and were among the volcanoes studied by AVO.
(Photo: Getty Images)
Great Sitkin volcano
Great Sitkin Volcano is a basaltic andesite volcano in the central Aleutian Islands that dominates the northern half of Great Sitkin Island, which is part of the Andreanof Group of Islands. It is the most active volcano in the world.
In terms of distance from Anchorage, it’s about 26 miles east of Adak, 1,192 miles southwest. As described by AVO, the volcano has a composite structure consisting of an ancient dissected volcano and a new parasitic cone with a 1.8 mile diameter summit crater as the centerpiece.
In an eruption in 1974, a steep-sided lava dome formed in the middle of the crater, occupying the entire interior. A massive explosive eruption on the southwest slope of the volcano occurred about 280 years ago, causing pyroclastic flows that partially filled the valley of Glacier Creek.
Read also: Photo of explosions from Mount Pavlof in Alaska, USGS raises alert level
The Pavlof volcano is a stratovolcano located 600 miles southwest of Anchorage on the Alaska Peninsula. The volcano is 4.4 miles in diameter and has active vents near the summit on the north and east sides.
The volcano has erupted more than 40 times in the past, making it one of the most active in the Aleutian Islands. The Aleutian Arc sits on the Pacific Ring of Fire, a volcanic hotspot.
The AVO has recorded earthquakes and small explosions over the past 48 hours. Despite the cloud cover, AVO estimates that these explosions probably produced low ash emissions.
Semisopochnoi is the easternmost place in the United States and North America, due to its geographic position on the globe at 179 ° 46 ′ East. It is located just 9.7 miles west of the 180th meridian, making it the most easterly land location in the world.
Located in the Aleutian Islands, Semisopochnoi is one of 14 large volcanic islands and 55 small uninhabited islands that form a chain. These islands, with their 57 volcanoes, form the northernmost part of the Pacific Ring of Fire. AVO reports that the north crater of Mount Cerberus is still erupting.
(Photo: Getty Images)
Due to its aerial appearance, many believed Kilauea was just a satellite of its larger neighbor, Mauna Loa. However, decades of investigation show that Kilauea has a magmatic plumbing system that reaches the surface at a depth of nearly 60 kilometers.
Its top is really part of a curved line that covers Mauna Kea and Kohala but not Mauna Loa. Mauna Loa is the the highest active volcano in the world at 13,681 feet above sea level.
The Mauna Loa eruptions are likely producing a large amount of rapid lava flows capable of impacting the eastern and western regions of Big Kona Island in Hilo.
Associated article: Kilauea volcano: a lava eruption sends “Pelé’s hair” in the sky of Hawaii
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