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Volcanowatch

April 9, 2009

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Volcanoes and Hula Dance to the Same Beat

Merrie Monarch 2009

Unless you've been sitting in a lava cave (the way we sometimes do) you should be well aware that this Sunday is the beginning of the annual Merrie Monarch festival—the world's premier event for watching and learning about the Hawaiian hula.

The hula kahiko, or ancient hula form, is always the crowd favorite on Friday night. The kahiko is one expression of the mo`olelo, or stories, of Hawaiian culture. Of course, a popular theme of hula performed during the Merrie Monarch involves stories of Pele, the Hawaiian deity of the volcano.

The hula of Pele uses rhythmic rising, falling, swaying, and flowing, accompanied by the oli, or chant, and beats of instruments to portray the likeness and action of Pele and the volcano as one inseparable entity. So it may be of little surprise to you that the rhythmic nature of the hula and chants describing the volcano would accurately portray of the bursting forth, and diminishing of such things like lava flows and explosions. But have you ever wondered if the rhythms of the hula have any relation to detailed scientific observations made at the volcano? The answer may be surprising to you; the connections go deeper than you think, and certainly deeper than we're aware of.

Much of the behavior of Kīlauea and Mauna Loa volcanoes are rhythmic in nature. The sounds, earthquakes, and ground swelling of these volcanoes, have all been found to follow rhythmic patterns.

Perhaps the most obvious rhythm of the volcano is the very sound the volcano makes. Anyone who has had the privilege of being near a lava vent can attest to the rhythmic sounds of gas and lava gushing from vents. This is the `uhi `uha sound in the hula chants that results from gases and gas-charged magma rushing through vents, or conduits, in the volcano. Much like a pahu drum, the size of the chamber controls the depth of the sound. These sounds actually extend well beyond the range of human hearing into a realm called the "infrasound". Geologists record and study the depth and breadth of these infrasonic beats to model the internal structure vents and conduits.

The shaking of the volcano also occurs with rhythmic frequency. In the current episode of eruptive activity at Kīlauea, something called episodic tremor has been frequently observed. Episodic tremor is a pattern of seismic activity, or shaking of the volcano, that occurs at semi-regular intervals. Patterns of seismic activity like this have been seen at Mount St. Helens where they were called "drum beat" seismicity. Episodic tremor at Kīlauea can be seen on seismic recorders as triangular-shaped bursts periodically placed—an imprinting reminiscent of a kapa-cloth pattern. A current interpretation is that episodic tremor is caused by the repeated rising and falling of the lava surface underground.

In addition to shaking, the volcano's entire body also sways, or deforms, in rhythmic ways. The ground surface of Kīlauea regularly rises and falls in cycles called deflation-inflation (DI) events. These events are linked to pulses of magma and gas which rise regularly under the summit of Kīlauea in the region of Halema`uma`u. An interesting consequence of magma migration is a coordinated dance of the ground surface at the summit and east rift zone of Kīlauea. As a pulse of magma rises up under Halema`uma`u, the summit of Kīlauea expands, rising upward. As this magma makes its way down the east rift the ground beneath Pu`u `Ō `ō begins to rise too. The dancers complete their turn over the course of a day or so.

The above descriptions only scratch the surface of many deeper rhythmic relationships that exist. So as you watch and hear the hula of Merrie Monarch this year, we encourage you enjoy the mo`olelo `o Pele and hula—both its sheer beauty and, also, its remarkable accuracy in describing the essence of volcanoes.

Activity update

The Waikupanaha and Kupapa`u ocean entries remain active. Surface flows inland from Kupapa`u, which began late last week following a deflation-inflation (DI) event at Kīlauea's summit, remain active along the eastern boundary of the National Park.

At Kīlauea's summit, the vent within Halema`uma`u Crater continues to emit elevated amounts of sulfur dioxide gas, resulting in high concentrations of sulfur dioxide downwind. Though not directly observed, vent noises suggest that lava is still present within the vent about 100 m (110 yds) below the floor of Halema`uma`u crater.

Visit our Web site (http://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 summary; email questions to askHVO@usgs.gov. skip past bottom navigational bar


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Updated: April 13, 2009 (pnf)