English: The Republic of Vanuatu consists of a group of mostly small, steep islands of volcanic origin. Located in the South Pacific Ocean, about three-quarters of the way between Hawaii and Australia, Vanuatu sits squarely atop the Pacific Ring of Fire – an area of high seismic and volcanic activity. There are nine active volcanoes within this small archipelago, seven of which are on land and two under the ocean waters.

On April 11, 2018, NASA’s Terra satellite flew over Vanuatu, allowing the Moderate Resolution Imaging Spectroradiometer (MODIS) on board to acquire a true-color image of activity at two active volcanoes: Ambrym and Aoba.

The northern-most volcano, Aoba, was actively erupting, sending a thick gray column of ash and gas into the sky. The ash rose underneath a layer of streaky gray-white clouds, masking the extent of the ash plume somewhat. After a lull in eruptive activity since the summer of 2011, activity resumed in autumn 2017. A brief period of quiet followed, but by mid-March 2018, Aoba volcano resumed active eruption, dropping ash across the island.

By April 14 the Wellington Volcanic Ash Advisory Center (VAAC) reported that the eruption at Aoba had ceased. South of Aoba’s ash plume, a gray streak crossed the sky from Ambrym volcano – a large basaltic volcano that is one of the most active volcanoes in the world. It has several active calderas, many of which contain small lava lakes. In late March, the Vanuatu Geohazards Observatory reported that the lava lakes in two of Ambrym’s craters continued to be active, producing gas-and-steam emissions. It is likely that the gray plume seen in the sky near Ambrym contains little, if any, ash but is made up of volcanic gas and steam.