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Volcanowatch

July 24, 2003

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


Awareness does not necessarily mean preparedness

It was heartening to see several delegates at last week's Cities on Volcanoes 3 (COV3) conference who were former students of the Center for the Study of Active Volcanoes (CSAV) at the University of Hawai`i at Hilo. Every summer, CSAV conducts two training sessions. The first course is for six weeks and is open to technicians and scientists from countries with volcanoes. The second is for university students seeking to learn more about volcano monitoring and hazards mitigation.

The CSAV courses stress the importance of what the Cities on Volcanoes conferences have been trying to achieve - an amalgamation of awareness and preparedness. A common refrain of the COV3 conference was that being aware of a hazard did not necessarily translate to getting prepared for the consequences. This is a dilemma worldwide - people think that nothing will happen to them, only to another person or at some other place. How to change this attitude is a problem that has to be solved.

This year's CSAV international course was scheduled so the students could participate in the COV3 conference. The 11 CSAV students came from Indonesia (2), the Congo (2), the Philippines, Nicaragua, Costa Rica, Colombia, Chile, Peru, and Papua New Guinea. In the last 10 years, over 90 students from 26 countries have taken the CSAV international course.

The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) supports the CSAV program with personnel, equipment and facilities. The popular field class for university credit starts on July 28 with a full complement of 16 students. Many graduates of this class have gone on to careers in volcanology with several working for the USGS.

On another topic, there was some confusion among the non-volcanologists at the COV3 meeting about the difference between volcanism in Hawai`i and the Pacific "Ring of Fire."

A simple explanation is that the magma sources for Hawaiian volcanoes and Pacific Rim volcanoes are different. Magma for Hawaiian volcanoes is supplied by a plume of hot rock rising from Earth's mantle near the middle of the Pacific plate. The location of this plume is called the "hotspot," and Mauna Loa, Kilauea, and Lo`ihi volcanoes are assumed to be over it now. The mantle plume is thought to be part of a convective cell current that powers the plate movement. A recent article in Science discusses the discovery of the possible mobility of the Hawaiian "hotspot."

Magma for volcanoes around the Pacific Rim form at converging plate boundaries. The oceanic plate subducts beneath the continental plate, and magma is generated by the partial melting of the overlying plate. If the surface of the overlying plate is on land, a volcanic mountain range is formed, such as the Andes and the Cascades. If the surface of the overlying plate is beneath the ocean, an island arc is formed, such as the Aleutians and the Marianas.

The longevity of the volcanoes also differs. A Hawaiian volcano, carried by the Pacific plate away from the "hotspot," has a finite life. It becomes extinct after its magma supply from the mantle plume is severed, and all residual magma within the volcano either erupts or solidifies. A Pacific Rim volcano has the ability to erupt as long as the plates continue to converge and produce magma.

Eruptions of the Pacific "Ring of Fire" volcanoes are often more explosive than Hawaiian eruptions. This is because of a basic difference in the chemical composition of their magmas. Hawaiian magma has less silica and volatiles than magma of Pacific Rim volcanoes. With less silica, Hawaiian magma has a lower viscosity, and that allows the volatiles within the magma to escape readily as the magma ascends toward the surface. Hawaiian eruptions tend to be effusive with the gas-depleted magma. On the other hand, the high silica magma of Pacific Rim volcanoes has a higher viscosity, and gas bubbles have difficulty leaving the magma as it rises. The pressurized bubbles explode out of the magma when the surface is breached and may create a huge ash column.

Whether "hotspot" or plate boundary volcano, people live on them, and as long as they place themselves at risk, there will always be a need for conferences such as COV3 and programs such as CSAV to mitigate the hazard.

Activity Update

Effusive eruptive activity at the Pu`u `O`o vent of Kilauea Volcano continued unabated during the past week. Glow is visible above Pulama pali, and two surface flows from the east-side lobe of the main Mother's Day flow wend their way down the pali to just above Paliuli. Lava continues to inflate the Kohola arm of the Mother's Day flow. The flow has advanced 600 meters (yards) beyond the base of Paliuli in the coastal flats. Occasional cascades are seen on Paliuli from the Kohola flow. Lava stopped entering the ocean at the Highcastle delta, and there is no ocean entry at this time.

One earthquake was reported felt on the island. Residents from Hilo to Volcano and from Pa`auilo, Papa`aloa, and Hale Pohaku felt the earth shake at 7:32 p.m. on Friday, July 18. The magnitude-3.3 earthquake was located 18 km (11 mi) northwest of Kilauea summit at a depth of 23 km (14 mi).

Mauna Loa is not erupting. The summit region continues to inflate slowly. Seismic activity remains low, with only two earthquakes located in the summit area during the last seven days. skip past bottom navigational bar


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Updated: July 29, 2003 (pnf)