The summit eruption at Kilauea volcano has provided geologists with a unique opportunity to see into the underground plumbing structure of Kilauea. It was long debated, for example, whether there was a direct connection between the shallow magma chamber below Kilauea’s summit and the Pu’u ‘O’o vent on the East Rift Zone. Also, was the lava in the lava lake at Halema’uma’u the same lava that erupted at the summit in 1982?

Chemically, it seems the lava  that is erupting at Pu’u ‘O’o is the same lava that is erupting at the Halema’uma’u vent. The only difference between the lavas is in the crystallization of minerals in the lava. The lava at Halema’uma’u is very, very hot (2,140 degrees Fahrenheit) with only small-sized olivine crystals within the lava. The lava at Pu’u ‘O’o is slightly cooler (2,100 degrees Fahrenheit) and contains a greater diversity of crystals, including olivine and pyrozene. While both minerals exist in Hawaiian lavas, they crystallize at different temperatures.

The presence of these crystals suggest a complicated system of magma recharging beneath Kilauea, with the lava erupting being a mix of gas-rich, crystal-less newer magma and older magma that had already partially crystallized in Kilauea’s magma chamber.

A recent article from the Hawaiian Volcano Observatory’s Volcano Watch column explains this process and mystery much better than I ever could. It’s an interesting read for anyone interested in petrology and Kilauea’s internal plumbing system in general.