Volcano Watch: What a day! Eruptions, earthquakes, and a lower lava lake


On the afternoon of April 30. 2018, an earthquake “swarm” in Hawaii Island began such that earthquakes started to occur far more frequently, up to 10 per hour. As this animation shows, a swarm of volcanic earthquakes began northwest of the summit of Kilauea Volcano on its East Rift Zone, a feature extending from Kilauea’s summit that carries magma underground through the flank of the volcano. The occurrence of these earthquakes then moved along the rift zone away from the summit, suggesting the movement of magma below ground in this direction. Magma reached the surface and erupted as lava on the afternoon of May 3 and is ongoing (6 May 2018). Since the eruption began the frequency of volcanic earthquakes has dropped to about 1 per hour. However, tectonic earthquakes that result from motion on faults became more common since the eruption, many larger than magnitude 4.0 with the largest having a magnitude of 6.9 on the afternoon of May 4.


Time-lapse thermal image movie of Halemaumau Overlook Vent. April 26, 2018 to May 6, 2018. Images courtesy of USGS/HVO

The summit lava lake has dropped significantly over the past few days, and this evening was roughly 220 m below the crater rim. This very wide angle camera view captures the entire north portion of the Overlook crater. Photo taken Sunday, May 6, 2018 courtesy of U.S. Geological Survey

The summit lava lake has dropped significantly over the past few days, and this evening was roughly 220 m below the crater rim. This very wide angle camera view captures the entire north portion of the Overlook crater. Photo taken Sunday, May 6, 2018 courtesy of U.S. Geological Survey

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

The USGS Hawaiian Volcano Observatory was unable to issue “Volcano Watch” by its regular Thursday deadline on May 3 due to unfolding events on Kīlauea Volcano. Little did we know that Friday would be even more hectic.

How it began: Following a collapse of the Pu‘u ‘Ō‘ō crater floor on Monday, April 30, an intrusion of magma migrated down Kīlauea’s East Rift Zone, advancing below ground toward Highway 130 and communities in the lower Puna District on the Island of Hawaiʻi. The possibility that the intrusion would lead to an eruption of lava became more likely as numerous small earthquakes shook the area over the next few days.

On Thursday, May 3, it happened! With little fanfare, steaming ground cracks were soon spewing lava in Leilani Estates.

By Friday morning, three additional fissures had opened in the subdivision, with lava traveling less than a few tens of meters (yards) from the vents.

Then, Kīlauea really started rocking and rolling. It began with a magnitude-5.4 earthquake at 11:32 a.m. HST. An hour later, a magnitude-6.9 earthquake, the strongest quake to strike Hawaiʻi since 1975, rattled residents across the island and beyond, with felt reports from as far away as Kaua‘i. Over the next 24 hours, more than 500 earthquakes—13 with magnitudes of 4 or greater—shook the island.

In the meantime, the summit of Kīlauea switched from inflation to deflation, and in concert with that deflation, the summit lava lake level began to drop.

Events of this notable day on Kīlauea are summarized in a photo essay featuring images from Friday, May 4, 2018.

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