Dr. Keith Horton

One of our most important CSAV instructors, Keith Horton, passed away in the fall of 2023. He died peacefully in his sleep, at the age of 75. Keith is the inventor of FLYSPEC, a gas correlation spectrometer instrument, which is far more lightweight and portable than its predecessor, COSPEC, and significantly less expensive. The FLYSPEC is typically mounted on a field vehicle (a car, truck, boat, helicopter, motorcycle), or even hand-carried by scientists, and driven or flown or walked in traverses beneath a volcanic plume. The FLYSPEC instrument continuously measures the amount of scattered ultraviolet sunlight energy absorbed by sulfur dioxide gas (SO2) emitted by the volcano. With software developed by Keith and colleagues, these measurements, in turn, can be used to compute the volcanic emission rate of SO2, in units of tons per day. This volcanic SO2 emission rate can then be used to estimate the rate at which lava is being erupted, a fundamental gauge of volcanic activity.

Keith's invention of FLYSPEC and his willingness to collaborate freely to refine the instrument greatly streamlined the USGS Hawaiian Volcano Observatory's vehicle-based SO2 measurements, and improved overall data retrieval and quality. This worked well for years, but when Kilauea's summit began erupting huge amounts of SO2 in 2008, vehicle-based FLYSPEC measurements became unreliable: the emission rates were simply too large to measure up close to the vigorously convecting lava lake. Keith responded with a novel idea to set out an array of permanent FLYSPECS perpendicular to the plume and farther downwind than the road used for vehicle measurements. Funded by the USGS, the array was fielded by Keith's company FLYSPEC Inc., and HVO scientists. The operational upward-looking FLYSPEC array began providing continuous SO2 emission rates every ten seconds during daylight hours under good field conditions. This new capability continues to help improve our understanding of how volcanoes like Kilauea work.

But besides teaching CSAV International, and providing the USGS Hawaiian Volcano Observatory with instrumentation for monitoring, Keith worked directly with many other volcano observatories. According to his colleague Jeff Sutton, there were

“16 countries around the planet where he collaborated with scientists on FLYSPEC-based measurements carried out on 30 volcanoes. It was Keith Horton’s intent to make this fairly sophisticated technology as easy to use as possible.”

Arif Cahyo Purnomo (CVGHM, Indonesia) reflects on the International course,

"I remember when Keith taught about FLYSPEC. Keith was a great instructor!"

Maria Concepcion Barairo (PHIVOLCS, Philippines) said,

"He was very open to any questions, and very eager to share his knowledge about something you can see he’s passionate about. The technology developed for SO2 monitoring has been helping us for so many years now, and I personally am very thankful for all the help he’s provided us all these years."

Eric Arcondo (PHIVOLCS, Philippines) writes,

“Dr. Keith easily and readily responded to our queries and consultations. Truly Dr. Keith's knowledge, expertise, and person will be missed in our community. His legacy will surely be remembered and applied. Thank you and salute to you, Dr. Keith Horton.”