In early August 2006, Merapi Volcano and Semeru Volcano acted up simultaneously. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard NASA’s Terra satellite took this picture of the volcanoes on August 2, 2006. In this image, Merapi is emitting a steady stream of ash and/or steam. Seremu’s plume (in the east) shows discrete bursts of activity that appear as puffballs of ash and/or steam, connected by a very thin stream. Semeru’s plume appears to shift direction, first blowing to the west, then to the south. Each volcano is topped by a hotspot, outlined in red, where the satellite sensor detected ground surface temperatures much hotter than the surroundings. In fact, numerous hotspots dot the island of Java in the top image. Thermal hotspots can result both from volcanoes and fires.
NASA image created by Jesse Allen, Earth Observatory, using data provided courtesy of the MODIS Rapid Response team.
Mount Merapi was gearing up for an eruption in late April 2006. It erupted in early May, sending searing gas down its slopes. The volcano followed this eruption with more emissions of steam and ash in the summer of 2006.