An American volcano that has been dormant for 800 years seems to be waking up

Activity has been detected under a dormant volcano near Sitka, Alaska. Mount Edgecumbe has been dormant for at least 800 years but, following a series of earthquakes in the area earlier this year, scientists have identified new signs that the sleeping giant may be awakening.

Research by the Alaska Volcano Observatory in conjunction with the Alaska Satellite Facility used mathematical modeling based on satellite imagery to determine that this recent increase in seismic activity was caused by the upward thrust of moving magma. deep below the Earth’s surface.

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“As magma moves, it can either work its way along fissures or form an expanding melt basin at depth, and both of these processes can cause small earthquakes,” said David Pyle, volcanologist at Oxford University. Newsweek.

“Seismometers can detect very small tremors and earthquakes – much smaller than what would be perceptible to a human. If we have an array of seismometers placed around a volcano, we can use the seismic signals to locate the place where earthquakes are triggered.”

As the magma rises to the surface, it also causes the land above it to swell, like a stretching balloon. “

Satellite radars are a very important tool for monitoring volcanoes. They can measure very small changes in the shape of the Earth’s surface,” Pyle said.

“As the magma moves deep into the upper few kilometers of the earth’s crust, we can see the slightly domed surface from these radar measurements. And we can combine that with the locations of earthquakes to determine in three dimensions the shape of the magma body inside the Earth.”

The United States has more volcanoes than any other country in the world, most of which are located in Alaska. The US Geological Survey has estimated that there are 161 potentially active volcanoes in the country, although only 42 of them have been active in the past 70 years.

Mount Edgecumbe is believed to have last been active 800 years ago, but according to geological evidence its last major eruption was around 4,500 years ago. As a result, many described it as being “dormant”.

“‘Dormant’ is a word often used to describe volcanoes that have not erupted in decades or centuries, and which may seem completely silent. But it does imply that dormant volcanoes could erupt again” , Pyle said.

“Most volcanoes have a life cycle that lasts hundreds of thousands of years. During this time, they can erupt as magma rises from deep within the Earth and reaches the surface. And then they can fall dormant again between eruptions, because the magma When another batch of magma rises under the volcano, then we might see the volcano become agitated again, or “reactivated.”

However, the recent increase in volcanic activity below Mount Edgecumbe does not necessarily mean that it will erupt again anytime soon.

“Detecting the movement of magma at depth is usually a reminder that a volcano is active, or potentially active, but it’s not necessarily a sign that a volcano is about to erupt,” Pyle said.

“Over the past 20 years, there have been many examples where scientists have used [satellite imagery and seismic activity] together to watch new magma arrive under a volcano. And in most of these cases, the disturbance subsides after a few weeks or months, without an eruption.”