It's worth remembering that Meru is a dormant volcano. The last recorded eruption was over a century ago, in 1910. It was moderate, ejecting stones and ash several kilometers high. Since then, there have been no signs of activity. Major eruptions occurred tens of thousands of years ago. In 2015, there were reports of ash ejection, but it turned out to be false – the smoke cloud above Meru was due to forest fires on the mountain.
Currently, scientists do not record any signs of possible volcanic activity. Upon reaching the crater rim, you'll be able to see the ash cone in Mt Meru's giant caldera.