Hawaii's Oahu Used to Be a Bigger Island

Sinton et al. (2014), GSA Bulletin

ScienceShot: Express Elevator From Hell

Molten rock spewing forth in volcanic eruptions may have risen dozens of kilometers through Earth’s crust in a few months rather than over millennia, a new study suggests. When researchers looked at crystals of the mineral olivine (inset) extracted from lavas erupted from Costa Rica’s Irazú volcano during a 2-year eruption that began in 1963, they found that about 15%  contained thin layers with higher-than-normal concentrations of nickel, an element found more commonly in Earth’s mantle than in the overlying crust. The chemical composition of each successive layer represents the environmental conditions that the growing olivine crystals experienced as they rose toward Earth’s surface, and the fact that nickel hadn’t diffused evenly throughout the mineral indicates that crystal-filled magma had risen from the mantle in a short period of time. Indeed, the scientists estimate that those layered crystals had risen through the estimated 35 kilometers of crust below Irazú volcano in as little as 4 months, they report online today in Nature. On average, though, magma migrated upward at about 80 meters per day, or more than 3 meters per hour, the team notes. It’s also in the same range of speeds seen beneath other peaks where networks of seismic instruments have detected deep earthquakes associated with the rapid movement of magma. But alas, deep quakes beneath a volcano may not serve as an infallible sign of an impending blowout (as seen in Italy’s Stromboli volcano, main image), the scientists say: Some peaks with deep quakes didn’t end up erupting, and many that did erupt didn’t show seismic signs of deep magma movement. For now, the signals that betray when and whether a peak will erupt remain elusive.