Many times, the volcanoes that have eruptions that last decades are ones like Kīlauea in Hawai'i, Yasur in Vanuatu or Erebus in Antarctica, where hot, runny basalt continuously erupts in lava lakes. However, when you look at the Global Volcanism Program's list of current eruptions, a few more explosive volcanoes jump out -- in particular, Shiveluch in eastern Russia.
Since 1999, the volcano has been producing frequent lava domes that then are spectacularly destroyed in massive explosions. In a bit of a "lather-rinse-repeat" pattern, Shiveluch just keeps on going decade after decade. You can see the before and during eruption on November 7-8 in the Terra and Aqua images above. Brown and grey ash is covering much of the peninsula to the east of the volcano. Another image (below) taken by Sentinel-2 (false color) shows some of the fresh ash fall and pyroclastic material as well as the dome itself.
