On March 19, 2008, an explosion within Halema`ma`u Crater heralded the start of a new eruption, the first at Kilauea's summit since 1982. Surprisingly, this eruption was not preceded by traditional indicators, such as earthquakes and ground swelling. Also unusual, Kilauea's new summit eruption occurred without interrupting activity on the volcano's east rift zone, which has been erupting nearly nonstop since 1983. Although lava is frequently visible deep within the summit vent, it has not erupted significant amounts of ash or spatter. Instead, it has emitted great quantities of volcanic gas, creating a major impact on Hawai`i Island's air quality. On the second anniversary of this unique eruption, Hawaiian Volcano Observatory volcanologist Mike Poland explores its possible causes, and discusses how Kilauea's summit eruption might evolve in the months and years to come.