Our Beautiful World
Lava flows are the most common of the direct volcanic hazards in Hawai'i. Flows may endanger people's property, livelihood, and peace of mind, but seldom their lives. The fronts of Hawai'ian lava flows generally move more slowly than the speed at which people walk, although the lava in the channel behind the front may be flowing much faster. On steep slopes a large flow could travel rapidly enough to endanger persons in its path. During the 1950 eruption of Mauna Loa, a flow front advanced at an average speed of almost 6 mph for over 2 hours.
The speed of a lava flow is determined not only by the steepness of the terrain, but also by the volume of lava that is erupted, because large flows tend to advance more rapidly than do small flows. The distance that a flow travels ultimately depends both on the eruption rate and on the duration of the eruption.
The chemical composition of lava will also affect
how rapidly a lava flows. Most Hawai'ian lavas are classified as basalts,
but within this category there are many types. Some basalts are more
The chief threat of lava flows to property owners
is that the flows may burn structures and bury land. There are other
effects, however, that may be almost as disruptive, as the Kalapana
community discovered during the repeated inundations of the area by
lava. In addition to destroying homes, the flows covered almost 2
miles of coastal highway. Some residents were forced to move when
the highway closures increased their daily commute by nearly 100 miles.
Many more residents in the Kalapana area were faced with financial
losses as land values
Even houses that are spared by the lava, however, may be rendered uninhabitable when the roads and utility lines leading to them are destroyed. By 1996, lava flows from Kilauea's eruption had covered 8 miles of the coastal highway, isolating the few structures that remained within the area.
To simplify land-use planning, the HVO have created
a hazard map of Hawai'i to illustrate the
the Hawai'ian hazard map, zone '1' is the most hazardous, '9' the