Categorized | Featured, Sci-Tech

Volcano Watch: ‘Two steps forward, one step backward’ style

Aerial view Feb. 11, 2010 of Kilauea Volcano’s south flank shows new lava flows in Royal Gardens subdivision (center) and the coastal plain (bottom center). Blue smoke (center right) is from burning vegetation caused by active lava flows. The developing lava-tube system is marked by the linear alignment of fume left of the burning vegetation, extending to the horizon. (U.S. Geological Survey photograph by Jim Kauahikaua)

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

Long-time Kilauea Volcano watchers know the drill when the supply of magma to the active vent on the volcano’s east rift zone is interrupted — abandonment of the “old” lava tube system, breakout of new surface flows, an evolving tube network, and eventually a new ocean entry.

This drama is unfolding again as many small aa and pahoehoe flows spread through what is left of the Royal Gardens subdivision and move a short distance across the coastal plain.

The flows are providing sporadic, distant views of incandescent lava, glow, and burning vegetation from the Hawaii County viewing area in Kalapana.

These flows are the consequence of a temporary decrease in magma supply to the active vent, beginning Dec. 29 and lasting nearly six days. The decrease corresponded to a pronounced deflation of the summit and east rift zone area, followed by several days of only slight inflation as recorded by sensitive tiltmeters.

Scientists interpret deflation as an indicator of a relative decrease in magma supply and inflation as an increase in magma supply.

When the Dec. 29 deflation event began, lava was pouring into the ocean at Waikupanaha, and more than 1,000 people per day were visiting the Hawaii County lava viewing area. Within a few days, however, the entry shut off completely.

Lava stopped entering the ocean by Jan. 4, but some lava continued to move through the uppermost part of the tube system within about 3 km (2 miles) of the TEB vent.

The upper tube system lies within a complex series of rootless shields tens of meters (yards) tall that were built by thousands of overlapping small flows between November 2007 and February 2008.

Near the lower end of these rootless shields, the original tube system became blocked as the Waikupanaha entry shut off, forcing lava to break out onto the surface at several locations between the shields and the top of Royal Gardens.

These flows are slowly creating a new but unstable tube system as the supply of magma to the vent continues to fluctuate. Seven deflation-inflation events have occurred since Dec. 29.

During the inflation periods, new breakouts from the tube have generally formed longer flows that reached lower and lower elevations on the pali. Breakouts from the next inflation period often start lower than the previous breakout—evidence that the tube system was elongating and forming longer flows.

The overall result of this pattern, as described by scientists, is a “two steps forward, one step back”-style of flow advancement and tube development.

Continued small fluctuations in magma supply as a consequence of small deflation-inflation cycles will likely promote growth of the new tube system all the way to the coast, west of the Waikupanaha entry.

But a larger- or longer-than-usual deflation event may cause the young tube system to stagnate and trigger new breakouts above Royal Gardens in a sudden step backward.

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