Out on the island of Unalaska sits Makushin. This volcano is covered in a thick layer of ice and snow and although it is not far as the crow flies from Dutch Harbor, it is extremely inaccessible. Yet, as part of its tasked mission, the Alaska Volcano Observatory must watch for signs that this volcano might be rumbling back to life.
Makushin is a volcano with a busy and sometimes violent history. The last known eruption from the caldera volcano was back in 1995 and over the past few centuries, Makushin has produced at least a dozen blasts. Some of these eruptions were as large as VEI 3 (something close to the same size as the 2010 eruptions at Merapi in Indonesia).
Go back far enough, and Makushin has generated even bigger eruptions, including a VEI 5 blast that created the caldera about 8,000 years ago. An eruption like that is more akin to Mount St. Helens in May 1980. This means watching for any restlessness at Makushin (and other Aleutian volcanoes like it) is important, both for people on the ground and people in the air flying over the region to Asia and back.
The view of Makushin in Alaska with Dutch Harbor/Unalaska in the foreground. The town is only 16 miles from the volcano. Credit: AVO/USGS.
Remote Monitoring of Volcanoes
So, just how can we tell? The most common methods to remotely monitor a volcano look at how the ground is shaking and what is coming out the top. Seems pretty obvious, right?
Seismometers can be installed on these remote volcanoes, with data collected from them sent by radio or satellite back to AVO to be interpreted. Many times these seismometers are installed during the brief windows of “good weather” and are powered by deep cycle batteries or solar cells (more of the former in places like Alaska).
need to be visited annually for maintenance or to be repaired if snow, ice, wind, bears or even people damage the instruments. It is best to have seismometers on the volcano you’re watching, but even more distant seismometers can record larger earthquakes happening at remote volcanoes.
Another common method that took off in the 21st century is webcams. You’d be surprised how many volcanoes in remote locations have some sort of webcam pointed at them, possibly mounted with the seismometers or at ranger stations or even at a distance that has a clear view of the volcano. Much like seismometers, webcams need maintenance as well. The biggest problem with webcams is weather and night. Can’t see much if it’s cloudy or foggy … or it is dark out, which happens a lot in the Alaskan winters.
A seismic station on Alaska’s Makushin seen in January 2020. Credit: AVO/USGS.
Where we can turn to remote sensing like satellites to fill in some of those blanks. Satellite like NASA’s Terra and Aqua, ESA’s Sentinel-2, the USGS/NASA LandSat fleet, Planet’s Doves — these are all earth-observing satellites that can look for plumes from volcanoes that pierce the clouds or drift out to see. They can also look for the infrared signature of lava domes. Even the weather satellites can get in the game, with GOES and Himawari catching plumes from their stationary orbits.
More specialized techniques have been used to look for signs of new activity at remote Alaskan volcanoes. Infrasound uses low frequency sound that can travel thousands of miles. These deep booms are explosions that might be happening at a cloud-shrouded volcano far out in the Aleutian Islands. Even looking for bouts of volcanic lightning can help pinpoint eruptions.
New Rumblings at Makushin
Put these all together and suddenly know a lot more about activity at these far-off volcanoes. That’s why AVO has raised the alert status to Yellow (second lowest of 4) at Makushin. Over the past few days, seismometers at the volcano have picked up a number of M3-4 earthquakes under the volcano — a potential sign that the volcano might be waking up from a few decades of quiet. Neither satellites nor webcams pointed at the volcano have seen any plumes, so no eruption has appeared to have happened so far.
However, once the signs start to appear, volcano monitoring agencies like AVO need to get the word out so that emergency managers can prepare. It might be for the towns near Makushin like Dutch Harbor or the airlines that fly over the area. Even so, this unrest is more than likely not leading to a new eruption — but it is much better to be too cautious than too cavalier when it comes to hazards. We can now see the signs much faster, and hopefully keep people safer.
Source : Discovermagazine