February 23, 1996

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

Volcanic Hazard in Hawaii

The "Volcano Watch" column first appeared on November 3, 1991. In the last four plus years, the staff and I have written 207 columns covering a wide range of topics, including updates on the ongoing eruption of Kilauea, hazards posed by that eruption, long-term volcanic and seismic hazards in Hawaii, as well as descriptions of volcanic and seismic events worldwide.

Through these columns, we have kept people informed about geologic events in a timely manner. More importantly, through the discussions of geologic hazards, we have enabled people to prepare for the earthquakes of the future, to avoid hazardous and potentially life-threatening areas near the eruption, and to plan development and growth on Hawai`i with an awareness of, and respect for, the types and frequencies of geologic events that occur here, including the ones that disrupt their lives.

This column will be the next-to-the-last that I will write because I will be leaving my current position as Scientist-in-Charge of the Hawaiian Volcano Observatory at the end of February and will be returning to the Mainland to a new job in early June.

The staff of the Observatory will continue to write the "Volcano Watch" column, as we all feel it is an important mechanism to inform the public about changes in volcanic activity, as well as about the geology of Hawaii.

I want to take this opportunity to reflect a bit on my four-and-a- half years here. These ruminations will form the basis of the remainder of this column and the column next week.

The Hawaiian Volcano Observatory plays a critical role in real-time monitoring of volcanic and seismic events in Hawai`i. We maintain the field instruments that warn of impending eruptions on Kilauea, Mauna Loa, Hualalai, and Haleakala. Each of these volcanoes has erupted in the past, and each will erupt again in the future. The question is when they will erupt, not if they will erupt. When they erupt, each will cause losses and disruption to life in the islands.

Many people on the island have been born since the current eruption of Kilauea began in January 1983. They cannot remember a time when Kilauea was not in eruption. For those a bit older, the present state of activity seems unusual, because Kilauea erupted only rarely, and usually briefly, prior to the current eruption.

Likewise, most people on the island think of Mauna Loa as erupting infrequently because there have been only two eruptions since 1950. However, in the hundred years before 1950, Mauna Loa erupted roughly every three years.

Hualalai is also a potentially dangerous volcano because it erupts every several hundred years. The occurrence of the last eruption in 1801 does not reduce the likelihood that it will erupt again in the next 50 to 100 years.

Haleakala, whose last eruption occurred in about 1790, has a similar eruptive history to Hualalai, with eruptions every several hundred years.

The need to quantify this information about the volcanic hazards on the islands led us to develop a lava flow hazard map for the Big Island that delineates the relative hazards of the different parts of the island. This hazard information should be one of many considerations for land-use planning and development of public and private infrastructure, such as schools, roads, telephone, water wells and water distribution systems, power plants and electric distribution systems.

The staff of the Hawaiian Volcano Observatory (past and present) has worked honestly and without bias to create a map that reflects the lava flow hazards on this island as best as we can determine them. Unfortunately, the misapplication of the hazards map has led to great frustration for many people living in the higher hazard zones due to unavailability of property insurance.

The average lava flow coverage in hazard zones 1 and 2 on Kilauea Volcano is slightly less than 30% in a 150-year period. Such coverage translates to a roughly 4.5% chance that any property will be lost to lava flows during the average life span of a house of 33 years in Hawai`i. These rough calculations indicate that the chance of loss each year is 0.14%.

This is not a huge risk and certainly one that can be accommodated by insurance rates that reflect the increased risk. I hope the insurance industry will rise to the challenge to fairly assess the added risks associated with properties located in more hazardous lava flow zones and to set rates that accurately reflect their increased risk.

The lava hazard zones have begun to be used in public or private land-use planning. In particular, the Puna Development Plan has incorporated lava hazards as an integral part of the plan. I feel that real reduction of future losses from eruptions will come about mainly through improved land-use planning and maintenance of low-density development in the highest hazard zones.

Thank you for reading these columns over the last several years. May all the geologic events in your future be ones for which you are prepared.

Aloha, Dave Clague.