USGS
Hawaiian Volcano Observatory

Lava-Flow Hazard Zones
Island of Hawai'i
Frequently Asked Questions

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" (right) was slightly revised and published as USGS Miscellaneous Field Studies Map 2193.

Lava-flow hazard zone-Hawaii Island

2. What does the Lava-Flow Hazard Zone Map show?

Nine lava-flow hazard zones for the volcanoes on Hawai'i Island (Kilauea, Mauna Loa, Mauna Kea, Hualalai, and Kohala) are shown on the map.

Zones 1-9, 1992 lava flow hazard 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 Kilauea 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?

Hazard map 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.

Scientist showing the lava flow hazard zone map 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?

Lava view area 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 Hawai'i Planning Department.

6. How were the lava-flow hazard zones determined?

lava flow 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?

Lava flow 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 Kilauea 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, HVO scientists collect gas samples from a fumarole on the rim of Halema`uma`u Crater. 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.

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.

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The URL of this page is http://hvo.wr.usgs.gov/hazards/FAQ_LavaFlowHazardZone/P1.html
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Updated: 15 March 2012 (pnf)