Frequently Asked Questions and Answers about Lava-Flow Hazards
1. Who prepared the Lava-Flow Hazard Zone Map for Hawai‘i Island?
The first maps showing volcanic hazard zones on Hawai'i Island were prepared in 1974 by U.S. Geological Survey geologists and were published in USGS Open-File Report 74-239. The lava-flow hazards map was reformatted in the 1980s, based on new and more complete geologic mapping and lava flow age-dating by USGS scientists.
In 1992, the "Map Showing Lava-Flow Hazard Zones, Island of Hawai‘i" was slightly revised and published as USGS Miscellaneous Field Studies Map 2193.
2. What does the Lava-Flow Hazard Zone Map show?
Nine lava-flow hazard zones for the volcanoes on Hawai‘i Island (Kīlauea, Mauna Loa, Mauna Kea, Hualālai, and Kohala) are shown on the map. The zones, ranked from 1 through 9, represent a scale of decreasing hazard as the numbers increase, based on the probability of coverage by lava flows.
The land area classified under Zone 1, the most hazardous, includes volcanic vents in the summits and rift zones of Kīlauea and Mauna Loa, Hawai‘i's two most active volcanoes. Zone 9, considered the least hazardous region, consists of Kohala, a volcano that has not erupted for 60,000 years.
3. Are the boundaries between lava-flow hazard zones distinct lines?
No, the hazard zone boundaries are approximate and gradational. The degree of hazard from one zone to the next is gradual rather than abrupt, and the change can occur over the distance of a mile or more. In other words, the boundary between lava-flow hazard zones is not a sharp line that, in one step, you can cross from one zone into the next. Also, within a single hazard zone, the severity of hazard from one location to the next can vary on a scale too fine to map. For example, the hazards posed by lava flows decreases gradually as the distance from eruptive vents increases.
Due to local topography, however, there can be abrupt changes in the relative lava-flow hazard within a single zone. For example, the hills behind Ninole stand high above the adjacent slopes of Mauna Loa and, consequently, are at a much lower risk from lava flows than the surrounding area.
4. Why did the U.S. Geological Survey prepare the Lava-Flow Hazard Zone Map?
The map was designed primarily to provide information for general planning purposes, so that critical community facilities could be sited in the safest possible areas. It also serves as an educational tool, to help Hawai‘i Island residents better understand the volcanoes on which they live, work, and play.
5. If the map was made for general planning purposes, why were so many building permits issued and so much construction allowed in Zones 1 and 2?
While the USGS prepared and made available the Lava-Flow Hazard Zone Map for general information and planning by land-use managers, there is no legislation requiring its use. The USGS provides hazard information but cannot advocate for, or require, its usage for a specific purpose. Thus, this question is best directed to the County of Hawaiʻi Planning Department.
6. How were the lava-flow hazard zones determined?
The hazard zones are based on the locations of probable eruption sites (based on past eruption sites), the likely paths of lava flows erupted from those sites (based on topography and the paths of previous lava flows), and the frequency of lava flow inundation of an area over the past several thousand years. The hazard zones also take into account structural and topographic features that would affect the direction of lava flows.
Our knowledge of past eruptions is based on written records beginning in the early 1800s, oral Hawaiian traditions, and the geologic mapping of, and age-date determinations for, lava flows on each volcano.
7. The Lava-Flow Hazard Zone Map is 20 years old. Is it still accurate?
Yes, the map is still accurate.
The map is intended to communicate long-term lava-flow hazards, rather than short-term hazards, which can change daily during periods of eruptive activity.
Hazard assessments are based on the assumption that future eruptions will be similar to those in the past. For the past 200 years, eruptions of Kīlauea and Mauna Loa have occurred at their summits and/or along one of their rift zones—and future eruptions on these volcanoes are likely to occur in the same areas.
8. Will the Lava-Flow Hazard Zone Map be revised?
As explained in #7 above, the map reflects long-term lava-flow hazards based on geologic data—the behavior of Hawaiian volcanoes over decades to centuries, the distribution and ages of lava flows and volcanic vents, the structure of the volcano, and topography. The map will not be revised until the geologic processes/structures/topography of the volcanoes change enough to warrant an update.
9. How can Hawai‘i Island residents determine the lava-flow hazard zones in which their properties are located?
The published Lava-Flow Hazard Zone Map (paper copy) was not intended to be used at a scale necessary to identify individual parcels on the map. However, digital mapping software can offer new options for this determination.
If you have access to Geographic Information Systems (GIS) software, you can overlay the lava-flow hazard zones and boundaries on the Hawai‘i County tax map. The County of Hawai‘i Planning Department includes the lava-flow hazard zone information on their GIS CD, which can be purchased for a nominal fee by contacting the Zoning Clerk at 808-961-8288. This will require installing the GIS browser software that comes with the CD.
HVO has also made available a Google Earth kmz file that displays lava-flow hazard zones for the County of Hawai‘i on the Google Earth base. Google Earth is an application freely available to anyone who has Internet connectivity.
The Hawaii Statewide GIS Program has the Island of Hawaii lava-flow hazard zones geospatial data available for download in a variety of formats.
More information on how to determine lava-flow hazard zones for specific parcels of land using GIS or Google Earth is provided in a 2006 "Volcano Watch" article, which is available on the HVO Web site.
10. How and why is the Lava-Flow Hazard Zone Map used by home insurance or mortgage companies?
As stated in #4 above, the map was designed for general planning purposes only. The following statement is included on the published map (USGS Miscellaneous Field Studies Map 2193):
Hazard-zone boundaries are approximate and gradational. These boundaries are not specific enough to determine the absolute degree of danger at any particular site. Lava-flow hazard maps are designed to show relative hazard across the Island of Hawai‘i and are meant to be used for general planning purposes only.
11. What can a home owner do if a company uses the map to set elevated insurance or mortgage rates?
An option is to contact the State of Hawaii Department of Commerce and Consumer Affairs.
The USGS Lava-Flow Hazard Zone Map is meant to convey relative volcanic hazard rather than risk (see "Hazard versus Risk" box).
A published study indicating the relative risk of lava inundation in Zones 1 and 2 is not available at this time, so inquiries or complaints about increased rates should go to the respective insurance or mortgage companies.
The question of who will create risk maps for Hawaii and other states with active, or potentially active, volcanoes is currently a topic of great interest.
|Hazard Vs. Risk|
|A volcanic hazard is defined as a destructive event that can occur in a given area or location, such as a lava flow or a volcanic earthquake, along with the probability of the event's occurrence. It is important to be aware of and understand the hazard, but, in a practical sense, nothing can be done to reduce the hazard itself—in other words, volcanic eruptions and earthquakes are beyond human control. Hazard assessments are done by physical scientists, such as the volcanologists at the USGS Hawaiian Volcano Observatory (HVO).
Risk, which is quite different from hazard, is defined as the hazard, multiplied by the vulnerability (the proportion of some resource, like people or land likely to be affected if the event occurs) multiplied, in turn, by the value (lives or property threatened). In shorthand: Risk = Hazard x Vulnerability x Value.
Risk can be mitigated—i.e., people can take actions to reduce their risk to a particular hazard. Risk assessment and mitigation involve social scientists who have expertise in determining "value" and "vulnerability" as defined in the above formula.
Example of hazard versus risk: In Washington, Mount St. Helens poses many volcanic hazards, such as lava flows and ash fall, as well as high risk, because nearby and surrounding communities (people) and associated infrastructure (homes, roads, schools, etc.) could be threatened by an eruption. On Jupiter's volcanically active moon, Io, there are abundant volcanic hazards, but no risk, because human lives and property are not threatened by the eruptions.
12. What can a home owner do if a lava-flow hazard zone is used as a reason for non-renewal of a home owner's insurance policy?
The USGS Lava-Flow Hazard Zone Map is meant to convey relative volcanic hazard rather than risk (see "Hazard versus Risk" box above). Insurance rates are based on risk related to those hazards as perceived by insurance companies. Any concerns about lava flow insurance should be communicated with the insurance company or the State of Hawaii Department of Commerce and Consumer Affairs.
13. How does location near a rift zone affect lava-flow hazards?
A rift zone is marked by vents through which lava is erupted. In other words, it is the first place that lava appears out of the ground and, therefore, the starting point of lava flows that can then travel downhill.
Kīlauea has two rift zones: the East Rift Zone and the Southwest Rift Zone (the latter is almost totally within Hawai‘i Volcanoes National Park). Mauna Loa has a Northeast Rift Zone and a Southwest Rift Zone. Hawai‘i Island rift zones are shown in gray on the map in question 3.
14. Why is an area freshly covered by lava designated as Zone 2, while another area not recently threatened by lava is designated as Zone 1?
Lava-flow hazard zones reflect the long-term hazard of lava flows, not the short-term hazard. Rate of lava coverage—not how recently lava covered an area—is the basis of long-term lava flow hazard.
Zone 1: "Includes the summits and rift zones of Kīlauea and Mauna Loa (left) where vents have been repeatedly active in historic time." These areas are the most dangerous because all, or nearly all, erupted lava first emerges from the ground within Zone 1.
Zone 2: "Areas adjacent to and downslope of active rift zones." These areas are also hazardous, but somewhat less so, because it takes some time for lava from Zone 1 to reach Zone 2.
As Kīlauea's middle East Rift Zone eruption has proven, damage from lava flows will be greater in Zone 1 than in any other zone over the long term. When the Pu‘u ‘Ō‘ō eruption began in January 1983, lava flows immediately and repeatedly covered Zone 1 areas. Zone 2 areas have also been covered by lava during the eruption, but not immediately or repeatedly. In other words, it took some time for lava flows to reach Zone 2 areas, and the threat was not continuous—it depended on which direction and how fast the lava flows moved downslope.
In 2018, the lower East Rift Zone eruption began in Zone1 and impacted areas in both Zones 1 and 2.
14a. As a specific example, why is Kalapana in Zone 2, while Leilani Estates is in Zone 1?
Kalapana is about 13 km (8 mi) downslope of Kīlauea's East Rift Zone. During Kīlauea's Pu‘u ‘Ō‘ō eruption, lava flows took 6 years to first reach Kalapana (in 1989) before the area was more completely inundated with lava over a period of about 9 months in 1990. Lava flows then spared this area for 20 years, until they once again threatened Kalapana Gardens in 2010-2011.
Leilani Estates, on the other hand, is located entirely on Kīlauea's lower East Rift Zone, and in 2018, an eruption started within, and immediately adjacent to, the subdivision. Prior to 2018, the two most recent lower East Rift Zone eruptions were in 1955 (left), when one of the vents erupted lava along the southernmost boundary of Leilani Estates, and in 1960, when lava inundated the village of Kapoho.
There is evidence of eruptive vents both north and south of Leilani Estates. But, unfortunately, many of the volcanic features indicative of the active rift zone—craters, cinder cones, steaming vents—are disguised by lush vegetation or have been removed by quarrying or grading, which leads to a false sense of security.
The concern was always "when"—not "if"—the next eruption will occur on Kīlauea's lower East Rift Zone with lava flows directly impacting Lelani Estates. That's exactly what happened in 2018, and what could happen again. Thus, the Zone 1 designation for the subdivision is appropriate.
15. Have lava-flow hazard zone maps been prepared for the other Hawaiian islands?
Hawaiian Islands In the Hawaiian Islands, there are six volcanoes classified as active: Kīlauea, Mauna Loa, Hualālai, and Mauna Kea on the island of Hawai‘i; Lō‘ihi, a submarine volcano southeast of Hawai‘i Island; and Haleakalā, on the island of Maui. These two islands—Hawai‘i and Maui—are the only ones for which lava-flow hazard zone information is available.
Lava-flow hazard zone maps are not available, and not needed, for the islands of Kaua‘i, Ni‘ihau, O‘ahu, Moloka‘i, Lāna‘i, Kaho‘olawe.
16. Where can Maui residents find lava-flow hazard zone information?
For East Maui, which includes the active volcano Haleakalā, the most current lava-flow hazard zone map can be found in a 2006 paper by D.R. Sherrod and others, available online. The Lava-Flow Hazard Zone classification used for Maui is similar to that used to classify lava-flow hazards on Hawai‘i Island, but, because Haleakalā erupts far less frequently than either Mauna Loa or Kīlauea, the relative hazards on Maui are lower.
A lava-flow hazard zone map is not available or needed for West Maui.
17. How do Maui lava-flow hazard zone numbers compare to those on Hawai‘i island?
The principal author of the 2006 paper by D.R. Sherrod and others, suggests that Maui Zone 1 is roughly equivalent to Hawai‘i Island Zone 3, Maui Zone 2 is roughly equivalent to Hawai‘i Island Zone 4, and Maui Zone 3 is roughly equivalent to Hawai‘i Island Zone 6. These comparisons are not explicitly stated in the paper, but Sherrod affirms how Maui lava-flow hazard zone numbers compare to Hawai‘i Island lava-flow hazard zone numbers, which were established by Mullineaux and others (1987). In other words, no place on Maui has volcanic hazards equivalent to Lava-Flow Hazard Zones 1 and 2 on Hawai‘i Island.
18. Where can I read more about lava-flow hazard zones in Hawai‘i?
The following two papers contain more detailed information about lava-flow hazards:
- Volcanic hazards in the Hawaiian Islands, chap. 22 (1987) by Mullineaux, D.R., Peterson, D.W., and Crandell, D.R. of Volcanism in Hawaii, Decker, R.W., Wright, T.L., and Stauffer, P.H., eds.; U.S. Geological Survey Professional Paper 1350, v. 1, p. 599-621.
- Distribution, 14C chronology, and paleomagnetism of latest Pleistocene and Holocene lava flows at Haleakalā volcano, Island of Maui, Hawai‘i: A revision of lava flow hazard zones (2006) Journal of Geophysical Research, v. 111, 24 p. Sherrod, D.R., Hagstrum, J.T., McGeehin, J.P., Champion, D.E., and Trusdell, F.A.
Other sources of information about volcanic hazards:
- Eruptions of Hawaiian Volcanoes—Past, Present, and Future (2010) U.S. Geological Survey General Information Product 117, 62 p. Tilling, R.I., Heliker, C., and Swanson, D.A.
- The Story of the Hawaiian Volcano Observatory—A Remarkable First 100 Years of Tracking Eruptions and Earthquakes (2011) U.S. Geological Survey General Information Product 135, 62 p. Babb, J.L., Kauahikaua, J.P., and Tilling, R.I.
- USGS Volcano Hazards Program—Understanding Volcanic Hazards