Saying "goodbye" to one GPS station and "hello" to two more.

Release Date:

On June 18, Hawaiian Volcano Observatory staff said a sad goodbye to a GPS instrument that had faithfully recorded over 95 m (310 ft) of downward motion of the floor of Kīlauea caldera before losing radio contact.

Subsidence of caldera floor impedes ability of NPIT GPS station to ...

Location of the NPIT GPS station, relative to the Hawaiian Volcano Observatory (HVO). Beginning on June 8, 2018, a portion of the caldera floor north of Halema'uma'u, where NPIT was located, began to slump into the crater. Over the next ten days NPIT GPS recorded down-dropping of 6-8 m (20-25 ft) with each summit explosion event, which have been occurring almost every day. This, together with earlier displacements, added up to a position change of 95 m (310 ft) down, 55 m (180 ft) south, and 5 m (16 ft) east. The large motions have now resulted in a misalignment of the radio shot between the instrument and the observatory, cutting off communication, and therefore data flow, from the GPS station.

(Public domain.)

The GPS instrument, called NPIT, first started moving downward in early May at the onset of subsidence at KILAUEA's summit. However on June 8, NPIT's motion picked up dramatically. This was when a portion of the caldera floor north of Halema'uma'u, where NPIT was located, began to slump into the crater. Over the next ten days NPIT GPS recorded down-dropping of 6-8 m (20-25 ft) with each summit explosion event, which have been occurring almost every day. This, together with earlier displacements, added up to a position change of 95 m down, 55 m south, and 5 m east (310 ft, 180 ft, and 16 ft, respectively).

These data provide unique insight into the crater collapse process, showing us that it is occurring as a series of steps instead of as continuous motion. Drone and helicopter views confirm that NPIT is still intact and likely still recording data. Unfortunately, the large motions have now resulted in a misalignment of the radio shot between the instrument and the observatory, cutting off communication and therefore data flow from the GPS station.

At about the same time that we lost the ability to contact NPIT, HVO staff completed work to add telemetry to two temporary GPS stations on the caldera floor. These two stations, called CALS and VO46, are not located on actively slumping portions of the caldera floor and therefore do not show the dramatic downward motion that NPIT did. However, they reveal that even portions of the caldera floor away from active slumping are moving downward very quickly; by as much as 1.0 m per day (3.3 feet per day) at station CALS. The data from these new stations can be viewed on the deformation page for Kīlauea.