The Maui News - Hawaiian Volcano Observatory geophysicists last week surveyed a dozen Global Positioning System sites atop Haleakala as part of a routine check on what is still considered an active volcano. According to the U.S. Geological Survey, the 10,000-foot volcano last erupted about 400 years ago. It was thought that the volcano last spewed lava around 1790, a date based largely on comparisons of maps made during the voyages in the late 18th century by French explorer Jean Francois de Galaup, Compte de La Perouse and British Capt. George Vancouver. But recent carbon dating of lava flows at Haleakala put the date of the last eruption in the 1600s, according to the USGS.

Jim Kauahikaua, scientist in charge at the Hawaiian Volcano Observatory, said there have been no signs so far of anything that would indicate that Haleakala could erupt any time soon. Scientists take measurements at the sites atop Haleakala—some of which need to be reached by helicopter—and compare those readings with data taken earlier. The last measurements for Haleakala were done in 2005. The scientists are looking for ground movements that might indicate a change in activity of the volcano. When magma accumulates beneath a volcano, it inflates, much like a balloon, and scientists measure the deformation to estimate the depth and amount of magma underneath.