December 21, 2020—Kīlauea summit interferogram

This “interferogram” was created from satellite radar data acquired over Kīlauea Volcano on December 6 and 21 (at 6 PM HST each day). The colored fringes show ground deformation that occurred during that 15-day period. Each fringe is equivalent to about 1.55 cm (0.6 in) of ground deformation towards or away from the satellite.

The interferogram reveals that the main part of Kīlauea Caldera subsided by about 4.5 cm (1.75 in) due to the eruption that started late on Sunday night. The style of the deformation indicates a shallow source, within a few kilometers of the surface.

There are also some closely-spaced fringes on the eastern edge of Halemaʻumaʻu crater. These fringes suggest greater magnitudes of deformation close to the eruption site, but unfortunately cannot be resolved due to the radar characteristics of the crater interior.

Overall, the story from this intererogram confirms what HVO has concluded from tilt and continuous GPS data—that deformation due to this eruptive event consists of slight deflation of the overall caldera due to magma drainage from the shallow reservoir, with more intense deformation happening only within a few hundred meters of the eruptive vents themselves.

No deformation was seen elsewhere on the volcano—for example, on the East or Southwest Rift Zone or the south flank. All of the action remains confined to the summit!

Data from Agenzia Spaziale Italiana COSMO-SkyMed satellite system.