Issue 9.5: October/November 2006

Lava Mixing

story by John Dvorak
photo by G. Brad Lewis


It is the most popular attraction in the Hawaiian Islands, out-drawing the USS Arizona Memorial almost two to one. The current eruption of Kilauea volcano, which began more than twenty years ago, has poured out nearly a cubic mile of lava, creating several hundred acres of new land. But what has been learned from this activity?


One major topic of research is how magma moves through the volcano. Before 1983, when Kilauea’s current eruption phase began, it was known that magma—that is, molten rock as it exists deep within the Earth—rose from below into a shallow storage chamber beneath the summit. From there, a small amount might erupt in the summit area, but most entered a conduit and flowed away from this chamber beneath one of two rift zones, from where it might later erupt.

That simple picture has been greatly amplified now that more than a thousand lava samples from the ongoing eruption have been analyzed.

Today, scientists know that new magma rising from below the earth’s mantle mixes with molten rock that is already stored—and partly cooled—inside the volcano. But the volcano only has so much capacity: Current estimates place the final mixing of new and old magma to have occurred by early 1985. Since then, all new magma has been flowing through Kilauea’s plumbing system, which begs an obvious question: How much longer can this eruption last?

No one knows. Scientists are much better at recognizing the signs of the beginning of an eruption than the end, and the continued flow of new, hotter magma through Kilauea has only made the whole plumbing system that much more efficient: More than half the volume of lava that has erupted from Kilauea in the last 160 years has been produced since 1983. Perhaps a major earthquake will end the current eruption; or the mantle source will be temporarily depleted; or it will be choked off, and a new eruption will start elsewhere on the volcano. But those events may not happen for decades, and the current eruption could outlive us all.

Hawaiian Volcano Observatory