Water and hot rocks and magma are not a good combination -- they create steam, and steam causes explosions. Such explosions can release tall clouds of ash and toxic gas and throw rocks -- so-called "ballistic blocks" -- as far as eight football field lengths.
This concern led to the latest warning from the Hawaii Volcano Observatory about the risk of explosions at the summit.
It's happened before. In April and May of 1924, the lava lake filling Halema'uma'u crater drained. The draining followed an intense sequence of earthquakes, suggesting that the magma was moving away from the summit reservoir. Once the lake fell below the height of the local water table, steam-driven explosions began.
Photographs from that time show the ash cloud rising miles into the sky. In fact, it was tall enough to reach the jet stream, which propelled the ash more than 10 miles away from the crater. The Hawaii Volcano Observatory website has a wonderful summary of the 1924 explosions, including magnificent historic photos.
Rocks thrown up by a steam explosion are a big hazard. Some weigh as much as 8 tons! (That's about 4 pickup trucks). Back in 1924, one person was hit and killed by a ballistic rock. Even the superintendent of the park at the time, Thomas Boles, was injured as he tried to escape one of these lava bombs.
In addition to rocks, ash is very hazardous to human health, as it can be a serious irritant to the eyes, skin, and the respiratory system.
Therefore, in the coming weeks it will be critical to follow the updates from the USGS and Civil Defense regarding the status of Kilauea, not only at the lava flow field down at Leilani Estates, but also at the summit. Once again, nature has provided us with a demonstration of its forces. We should seize this opportunity to learn from it as much as we can, together.
Continue reading at CNN.com