For decades, the state has been trying to reduce our dependence on fossil fuels. Energy from Hawaii’s geothermal resources is but one of several alternate energy sources that have been explored.
In Hawaii, geothermal resources depend on volcanic heat. Magma, stored in rift zones, heats groundwater that can be tapped by drilling. It is then pumped to the surface, where its heat is extracted to drive electrical generators.
It makes sense that the most attractive geothermal target in the state is also the most active volcano — Kilauea. The nearly continuous supply of magma to Kilauea pumps heat into the geothermal resource, but it also fuels eruptions that could threaten structures on the volcano.
To make clear where future lava flows are most likely, Hawaiian Volcano Observatory scientists published Lava-Flow Hazard Zone Maps as early as 1974, designating the summits and rift zones of Kilauea and Mauna Loa volcanoes as the most hazardous. For Kilauea, the summit and rift zones of the volcano also have the highest geothermal potential, so the Lava-Flow Hazard Map closely resembles the geothermal resource map.
Geothermal resources definitely exist on Kilauea, as established by a pilot project in the 1970s. The Puna Geothermal Venture commercial power facility has produced 30 megawatts from Kilauea’s heat, 20 percent of the annual electrical usage of the island of Hawaii, since 1993.
The most recent study in 2005 suggests the potential of the Kilauea resource, excluding areas within national parks and state reserves, could be between 250 and 600 megawatts. Development of geothermal resources may also be possible on volcanoes with less frequent eruptions than Kilauea, such as Hualalai, Haleakala or Mauna Kea.
If a resource of this size exists and is fully developed, the power generated from it would far exceed the need for electricity on the Big Island Therefore, the state is proposing the use of an undersea cable to link Hawaii, the potential major energy producer, and Oahu, the major energy consumer.
But what about the risk posed by volcanic eruptions? In a 1994 USGS publication (pubs.usgs.gov/of/1994/0553/report.pdf), observatory scientists estimated a high probability of eruptions from Kilauea’s lower east rift zone within any 50-year period. The publication also found a significant likelihood of lava inundation along the cable pathways linking the proposed Kilauea geothermal developments to the Honolulu energy grid, because the cable would have to pass across the northeast flank of Mauna Loa, Hawaii’s other very active volcano.
These threats are real. In the last 200 years, eruptions have occurred three times in the lower east rift zone of Kilauea and six times on the northeast flank of Mauna Loa. The possibility of an eruption in the geothermal resource or statewide cable path within any 50-year period is between 60 and 90 percent.
The effect of an eruption within a geothermal power development could be severe, and the site could be deeply buried by lava.
The power generated by the geothermal facility would be lost — possibly for weeks, months, or even years. The 1840, 1955 and 1960 eruptions in lower Puna continued for weeks to months. Power generation and transmission could not resume until after the eruption ceased, and it was safe to re-enter the area and re-establish the facilities and the cables carrying electricity away from the site.
With enough lead time before an eruption, however, much of the power-generation equipment might be moved offsite and saved for future use.
The effects of an eruption would be more profound as the geothermal power development increased in size. If a 500-megawatt power generation facility were developed within the lower east rift zone of Kilauea and power exported to Oahu and Maui, a volcanic disruption would have statewide effects.
As a community, we should explore all options in our quest for inexpensive, reliable electricity. There are downsides to the use of any energy source, and we must balance the negatives with the positives when making choices. This includes balancing the considerable benefits of geothermal resource development with the inherent risk of such development on active volcanoes.
Kilauea activity update
A lava lake within the Halemaumau Overlook vent resulted in nighttime glow visible from the Jaggar Museum overlook during the past week. The lake has been about 200 to 260 feet below the floor of Halemaumau Crater and visible by HVO’s webcam through much of the last month. This past week, the level fluctuated slightly because of several deflation-inflation cycles at the summit.
On Kilauea’s east rift zone, surface lava flows on the pali and coastal plain continued to be active. Over the past week, the flow front has not advanced significantly and has lingered near the boundary of Hawaii Volcanoes National Park about 0.6 mile from the coastline; there was no active ocean entry. Within Puu Oo, a lava pond was active in the eastern portion of the crater.
No earthquakes were reported felt across the island during the past week.
Visit the HVO website at hvo.wr.usgs.gov for detailed Kilauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.