Indonesia’s Mount Sinabung has been sporadically active since 2010, following four centuries of quiet. On February 19, 2018, the stratovolcano on the island of Sumatra erupted violently, spewing ash at least 5 to 7 kilometers (16,000 to 23,000 feet) into the air over Indonesia. At 11:10 a.m. local time (04:10 Universal Time) on February 19, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured a natural-color image of the eruption, just a few hours after it began.

According to reporting from the Associated Press, the erupting lava dome obliterated a chunk of the peak as it erupted. Plumes of hot gas and ash rode down the volcano’s summit and spread out in a 5-kilometer (3 mile) diameter, while ash falls were recorded as far away as the town of Lhokseumawe, some 260 kilometers (160 miles) to the north.

Villages were coated in ash, and airline pilots were given the highest alert for the region. Government officials handed out face masks to the citizens of the island and advised them to stay indoors due to the potentially dangerous air quality. As volcanologist and blogger Erik Klemetti put it: “breathing volcanic ash is a significant health hazard—the ash is really small shards of glass, so it can abrade your lungs and form a ‘cement.’”

The volcanic plume also contained sulfur dioxide (SO 2 ), which can irritate the human nose and throat when breathed in. The gas reacts with water vapor in the atmosphere to produce acid rain, and it also can react with other gases to form aerosol particles that cause haze and, in extreme events, climate cooling. The map above shows concentrations of SO 2 as detected at 1:20 p.m. local time (06:20 Universal Time) on February 19 by the Ozone Mapper Profiler Suite (OMPS) on the Suomi-NPP satellite. Maximum gas concentrations reached 140 Dobson Units.

Other sensors on NASA satellites have also been monitoring Sinabung. According to data from CALIPSO, some debris and gas from the eruption appear to have risen 15 to 18 kilometers in the atmosphere. (Click here and look at the data near 3° North and 98° East.) Volcanologist Simon Carn of Michigan Tech also noted via Twitter that the OMI instrument on the Aura satellite had recently detected rising SO 2 emissions around Sinabung, a sign that fresh magma was approaching the surface.

Click here to see video of the dramatic first moments of the eruption.

NASA Earth Observatory images by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC), and MODIS data from LANCE/EOSDIS Rapid Response. Story by Mike Carlowicz.