Catching the next axial eruption
Axis Seamount Map
Columbia University researchers recently completed a six-day research cruise on the R/V Marcus G.Lances, deployed 15 undersea seismometers on Axial Seamount, an undersea volcano in the northeastern Pacific that erupted in 1998, 2011 and 2015. The cruise is part of a two-year experiment in the predicted time window for the next eruption.The researchers hope their instrument will help capture the next eruption, improving our understanding of how magma and fissures on the ocean floor interact in volcanoes, and possibly providing insights into eruption forecast.
Felix Waldhauser, chief scientist at Columbia Climate Institute Lamont-Doherty Earth Observatory Yen Joe Tan of the Chinese University of Hong Kong, Dax Soule of Queen’s College, and 15 students and postdocs from New York, Seattle and Hong Kong were accompanied. The NSF-funded project is led by William Wilcock of the University of Washington and co-led by Waldhauser, Maya Tolstoy (UW), and Yen Joe Tan.
The expedition started in Newport, Oregon on September 3 and ended in Seattle on September 8. In the journal below, Theresa Sawi, a doctoral student in Columbia’s Department of Earth and Environmental Sciences and the Lamont-Doherty Earth Observatory, shares her thoughts and more about the science behind the expedition.
Photo: Teresa Savey
submarine seismograph
September 4
The first leg of our journey is underway. We’ve left Newport, Oregon, and we’re about halfway through our 300-mile drive to Axial Seamount. Axial is an underwater volcano on a mid-ocean ridge, where two plates move apart from each other at about the speed of a fingernail. As the plates expand, the decompressed magma flows to the surface, forming new oceanic crust. Axial seamounts are also located above “hot spots” – large bodies of buoyant magma. These two processes — spreading ridges and hotspots — are responsible for all of Axil’s volcanic and other geological activity.
The Pac-Man-shaped survey helped confirm the location of the undersea seismometers.
We will deploy 15 seafloor seismometers in and around Axial. The instruments record tiny vibrations in the ground and will be used to study and infer seismic and volcanic activity at the site. A year from now, scientists will come back for the instrument, but until then, we don’t know what the data looks like, or even if the instrument is working well. That’s why our scientists take great care in testing and calibrating instruments before deployment.
There are 15 scientists on board, ranging in rank from professor to undergraduate researcher and in between. Universities we represent include universities in Hong Kong, New York and Washington State. Although most of us have never met before, our passion for ocean science and interest in monitoring axial seamounts brought us together. Fingers crossed it didn’t break out until we left!
September 5 at 4:45 a.m. local time
We started our first watch today. My shifts are 4-8am and 4-8pm; great watch to catch some fabulous stars! Our watches are all used to monitor and record when the crew lowers the subsea seismometers from the side of the ship. We take notes as they wind them up with a crane called an “A-frame” and then release them into the water. We have deployed 5 instruments so far and will be turning back to investigate them later. Measurements are made by circling the ship’s instruments in a “Pac-Man” shape and probing them with sonar. We have to do this to check their final location, as ocean currents may have moved them from where they originally landed. The batteries in the seismograph last about a year, so another ship would have to be there to retrieve them by then. They did this by using sonar commands to release the anchors on the seismometers, allowing the instruments to float to the surface and be retrieved.
Once you get used to the swing, life on the boat is pretty easy. There’s a gym (try the 10-foot treadmill!), a library and recreation room to kill time, and they provide us with good food. Some of us like to look for whales or dolphins on the deck. A large group of dolphins showed up yesterday!
I’ve been sleeping – it’s a sign of seasickness. It’s not the quietest place to close your eyes, but there’s nothing better than being rocked to sleep.
September 6, 18:29 local time
Time flies so fast on a boat! We have deployed and measured all the seismometers and now we are measuring a hydrophone. Unlike seismometers, which record ground vibrations, hydrophones pick up vibrations transmitted from the ground to the water column. The hydrophone is sensitive to small earthquakes, and we deployed it outside the main area around Axial Seamount in order to understand seismic activity in the wider area. This is in stark contrast to seismometers, which are all deployed directly on or around volcanoes. Arrays of hydrophones have been deployed around the world for decades as part of efforts to monitor nuclear explosions.
Another important task we have on board is to regularly measure the speed of sound in seawater using small diving probes called disposable deep sea thermometers or XBTs. XBT is a consumable item because we literally dropped it in the water and never came back! As it falls, it transmits salinity, temperature and calculated speed of sound back to the lab via a thin copper wire over 1,500 meters long. For all our sonar-based ranging work, it is important to accurately measure the speed of sound. I’ve always been impressed with the amount of work that goes into collecting seismic data.
September 7
The cruise has ended and we are returning to the mainland! The expedition was a resounding success, with all 15 seismometers and one hydrophone being successfully deployed. After all the science was done, we had some free time to visit the cabin and bridge. The engine room houses an impressive array of machines and tools, from bow thrusters to septic systems, all designed to keep the vessel functional. Honestly, it was so loud that we had to wear ear protection, which prevented us from hearing any part of the trip – but things did look impressive!
On the bridge, we chatted with the captain about how they steer the ship, how to be the captain, and the various instruments on board. Interestingly, they still have the tools for celestial navigation, just as navigators have used them for thousands of years. We ended the tour by looking at a map of the Washington coast, our destination for tomorrow. We will sail across the Strait of Juan de Fuca into Elliott Bay, where we will enjoy a beautiful view of the Seattle skyline, and leave our boat.
It was a short but amazing trip. I am forever astounded by the sheer amount of effort and resources that go into collecting scientific data, and I am grateful to be a part of the process. I can’t wait to see what kind of data we collect. To all of you who enjoy these diaries, I wish you all the best of luck!
