Lava Flow Hazard Zones
| Zone | Covered since 1800 | Covered last 750 yrs | Notes |
|---|---|---|---|
| 1 | >25% | >65% | Highest hazard |
| 2 | 15–25% | 25–75% | |
| 3 | 1–5% | 15–75% | |
| 4 | ~5% | <15% | |
| 5 | None | ~50% | |
| 6 | None | Very little | Kailua-Kona |
| 7 | None | None | |
| 8 | None | None | |
| 9 | None | None | Lowest hazard |
Maps showing volcanic hazard zones on the island of Hawaii were first prepared in 1974 by Donal Mullineaux and Donald Peterson of the U.S. Geological Survey and were revised in 1987. The current map divides the island into zones that are ranked from 1 through 9 based on the probability of coverage by lava flows. Other direct hazards from eruptions, such as tephra fallout and ground cracking and settling, are not specifically considered on this map; however, these hazards also tend to be greatest in the areas of highest hazard from lava flows.
The island of Hawaii is divided into zones according to the degree of hazard from lava flows. Zone 1 is the area of the greatest hazard, Zone 9 of the least.
Hazard zones from lava flows are based chiefly on the location and frequency of both historic and prehistoric eruptions. "Historic eruptions" include those for which there are written records, beginning in the early 1800's, and those that are known from the oral traditions of the Hawaiians. Our knowledge of prehistoric eruptions is based on geologic mapping and dating of the old flows of each volcano. The hazard zones also take into account the larger topographic features of the volcanoes that will affect the distribution of lava flows. Finally, any hazard assessment is based on the assumption that future eruptions will be similar to those in the past.
Hazard zone boundaries are approximate. The change in the degree of hazard from one zone to the next is generally gradual rather than abrupt, and the change can occur over the distance of a mile or more. Within a single hazard zone, the severity of hazard may vary on a scale too fine to map.
There may be abrupt changes, however, in the relative hazard because of the local topography. 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, even though the entire area is included in a single zone. To determine the hazard differences within a single zone, more detailed studies are required.
The four major volcanic areas of the Big Island — Kilauea, Mauna Kea-Kohala, Hualalai, and Mauna Loa — each have different hazard profiles. Most of Kona falls in Zones 3–6, which means low to moderate historical lava coverage. Zone 9 properties (no lava coverage in recorded history) are generally the safest. Kailua-Kona itself is predominantly Zone 6, making it one of the more desirable areas from a lava hazard standpoint.