This photograph, taken from the International Space Station in 2015, looks eastward: Java is in the foreground, Bali and Lombok are near the center, and smaller islands trail off toward the horizon. The brightest reflection of the Sun off the sea surface silhouettes Surabaya, Indonesia’s second-largest city of almost 3 million. Against this background of glint as well as regional smoke, a line of volcanoes appears in sharp detail. Volcanoes are the backbone of the islands, which have been formed by the collision of the Australian tectonic plate (right) with the Asian plate (left). The name of each volcano appears in italics. White plumes – each about 80 km (50 mi) long – show that at least six volcanoes appeared to be emitting steam and smoke. The plumes are strikingly parallel, aligned with winds from the northeast. Image courtesy of NASA.