The Nevado del Ruiz volcano in Colombia hasn’t erupted in over 20 years, but there are signs that point that it’s entering a more active phase. INGEOMINAS scientists did a flyover with the Colombian Air Force and discovered ash on the glacier, near the crater rim, and more ash on the eastern flank.
This has likely come from an explosion on February 22nd. The steam plume on that day was about 1.4km high (4,500 feet). There was also a signal of a seismic tremor with multiple small ash emissions along with an increase in sulfur dioxide emissions. The summit at Ruiz is heating up and there will likely be some phreatic explosions. The increase in sulfur suggests that there is new magma in the volcano. Shots of the summit clearly show steam emanating from the crater, though there has been no new material in the crater itself.
Photos of the entire summit show ash on some of the snow-covered areas as well. The last time that Nevado del Ruiz erupted was back in 1985 and it killed over 23,000 people. A small eruption at the summit created a lahar that melted an abundance of ice and snow. There is plenty of snow and ice to make new lahars, so Ruiz is expected to be a real hazard if it enters a new period of eruption.