Despite the recent focus on Tonga’s main volcanic eruption, the USGS continues to monitor volcanoes in the United States.
Currently four are at high Watch/Orange status due to activity altogether.
(Photo: Getty Images)
Volcanoes placed in high standby/orange status
Great Sitkin Volcano, Pavlof, Semisopochnoi and Kilauea are the four volcanoes showing signs of unrest or activity.
Hawaii’s Mauna Loa volcano remains in yellow/advisory status, while all other USGS-monitored volcanoes are GREEN or unclassified, according to Weather Boy.
In the United States, the USGS monitors 161 potentially active volcanoes, most of which are in Alaska. There are over 130 volcanoes and volcanic areas in Alaska that have been active over the past 2 million years. AVO also investigates the 50 that have been in operation since the mid-1700s.
In Hawaii, Kilauea, Mauna Loa, and Hualalai are all active volcanoes, but only Kilauea is currently erupting; the other three are considered potential hazards.
Only a small percentage of the world’s volcanoes are found in the United States; the USGS estimates that there are about 20 active volcanoes at any given time.
Globally, there are about 1,500 potentially active volcanoes, according to the USGS, 500 of which have erupted in recent history.
Those in Hawaii are under the watchful eye of the Hawaii Volcano Observatory, while those in Alaska are under the watchful eye of the Alaska Volcano Observatory (AVO).
In addition to AVO and HVO, there are four other volcanic observatories: the Northern Mariana Islands Volcano Observatory, the Cascades-Yellowstone Volcano Observatory, and the California-HVO.
These additional USGS volcanic observatories monitor volcanoes in their particular geographic areas. Other observatories have reported no unusual activity or signs of more than background noise at this point.
Read also : USGS lifts yellow warning on 6 active volcanoes in US for ‘high unrest’
An aviation code is published by the US Geological Survey and volcanic observatories in the United States. There is a unique aviation code for each color. A volcano is labeled “unassigned” if there is insufficient ground data to determine whether or not it is active.
Yellow indicates that a volcano is showing signs of elevated unrest above known background activity levels, while green indicates typical activity associated with a non-eruptive condition.
When a volcano shows signs of increased or increasing instability, its color turns orange. At any time, the code turns red, indicating that an eruption is about to occur or is already in progress with considerable emissions of volcanic ash into the atmosphere.
Volcanic activity alert levels can range from normal in nature to advisory, watch or warning. If there is not enough data, it is simply designated as “unassigned”, as is the case with aviation codes.
At a steady background level of activity, the volcano is considered normal until it erupts. If the volcano shows signs of greater disturbance above baseline, an advisory will be issued.
A watch or warning is issued whenever a volcano shows indicators of increased or developing instability.
(Photo: Getty Images)
Active volcanoes around the United States
Located in the center of the Aleutian Islands, Great Sitkin Island is home to Great Sitkin Volcano, a basaltic andesite volcano that towers over the northern half of the island. It is 1,192 kilometers from Anchorage, about 26 miles east of Adak.
According to the American Volcanological Organization (AVO), the volcano consists of an older dissected volcano and a younger parasitic cone with a 1.8 mile diameter crater at its peak. According to AVO, Great Sitkin may still be erupting lava.
In Alaska, Pavlof Volcano is a stratovolcano located just over 600 miles southwest of Anchorage. The 4.4 mile diameter volcano has active vents near the summit on the north and east flanks.
The USGS estimates that the volcano has erupted more than 40 times in its history, making it one of the most active in the Aleutian Arc. Located on the Pacific Rim of Fire, the Aleutian Arc is a volcanic hotspot.
Low-level eruptive activity at Pavlof continued, according to AVO, and satellite photography showed elevated levels of activity over the past day.
Related article: A rare super-eruption of volcanoes can have catastrophic effects on the global climate
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