Kilauea coughs up a plume of ash

Kilauea Volcano put on a show of white and brown plumes Wednesday afternoon after an earthquake south of the summit.

Instruments pinpointed the location of the quake about five miles south of the summit, the Hawaiian Volcano Observatory said in its Thursday "Volcano Watch."

Minutes later, a staff member saw a "dense, brown plume ascending into white clouds." The brown plume continued from the Halemaumau vent for several minutes and slowly changed back to white.

The white plume is mostly steam while the brown plume contains more rock dust, the scientists said.

With the continuing Halemaumau plume since March, the observatory said, "We've been challenged by a diverse collection of seismic signatures whose patterns we're still trying to organize and understand."

Also recorded with the earthquake Wednesday was what the scientists call a VLP (very long period) tremor, with vibrations occurring over tens of seconds.

Halemaumau's explosions and brown plumes this year seem to correlate with VLP signals, the scientists said. "We've also observed small earthquakes, possible rockfalls and higher-frequency tremor bursts."

The brown plume emissions appear to be triggered by rocks and debris falling on top of a degassing lava column beneath the vent, the observatory said.

The very long period tremor "could signal pressure adjustments within the conduit as the falling material interacts with the degassing lava," it said.