Kilauea Activity Update

Kīlauea Activity Update

The lava flow from Puʻu ʻŌʻō that began on June 27, 2014, remains active and is advancing across State land east of the Wao Kele O Puna Forest Reserve. As of Thursday, December 4, the tip of the flow was about 3.9 km (2.4 mi) upslope from the intersection of Highway 130 and Pāhoa Village Road near the Pāhoa Marketplace. There was no significant change in activity at Puʻu ʻŌʻō.

The level of the summit lava lake within Halemaʻumaʻu Crater fell during the early part of the week, mimicking deflation at Kīlauea’s summit, but was rising again by December 3, in concert with summit inflation. As of Thursday morning, December 4, the lava lake was about 64 m (210 ft) below the rim of the Overlook crater, up from a low of 70 m (230 ft) measured two days earlier.

No earthquakes were reported felt in Hawaii during the past week.

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Visit our Web site (hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov.

What's going on? Withdrawal of magma or the movement of Kilauea's south flank or both?

The ongoing subsidence of the summit is thought to result mainly from magma movement out of the summit reservoir and into the east rift zone at a faster rate than it is being supplied from below (the hot spot beneath the Big Island). But other deformation surveys show that the subsidence has also been accompanied by the spreading or widening of the summit area and deformation of the rift zones. This broader region of deformation has led some scientists to suggest that another process--the movement of the volcano's south flank--may account for some of the subsidence.

Although the summit area of Kilauea has steadily subsided since the beginning of the Pu`u `O`o-Kupaianaha eruption, it has been subsiding and spreading (widening) at varying rates since a magnitude 7.2 earthquake occurred 9 to 10 km beneath the south flank of Kilauea on November 29, 1975. The earthquake probably originated as movement of the south flank along a broad slip surface defined by the boundary between the volcano and the underlying sea floor. Parts of the south flank moved suddenly seaward 3 to 8 m and subsided 1 to 3.5 m during the earthquake.

Scientists have long measured the seaward movement Kilauea's south flank and noticed correlations with intrusions of magma into the volcano's rift zones, eruptions, and large earthquakes. Three main hypotheses have been proposed to explain the fundamental cause of the south flank's mobility:

1. repeated forceful intrusion of magma into Kilauea's rift zones, which forces the volcano apart
2. gravitational settling of the entire south flank due to its enormous mass
3. the presence of a deep magma reservoir system beneath the summit and rift zones

Thus, in addition to the withdrawal of magma from the summit reservoir since 1983, part of the subsidence and spreading at the summit may also be related to continued movement of the south flank since the 1975 earthquake.

Deformation of the summit, rift zones, and south flank of Kilauea continues to be a major focus of the monitoring program at the Hawaiian Volcano Observatory. Ongoing research into the underlying causes of the volcano's movement is sure to improve our understanding of how Kilauea responds to gravity and its magma reservoir system.

 The URL of this page is http://hvo.wr.usgs.gov/howwork/subsidence/ 

Contact: hvowebmaster@usgs.gov