Recent Activity at Ol Doinyo Lengai

The most recent account of activity occurring at Ol Doinyo Lengai is from January 14, 2008.  A group of visitors were approximately 50 meters from the summit when the volcano experienced a mild eruption[1].  A large shower of stones rained down upon the group, forcing them to flee.  Reports indicate that some stones were as large as footballs[2].  Although a guide reported a lava flow, it is likely that he merely feared lava, because no lava flows were actually seen[3].  Moderate ash eruptions were also reported in the week after the eruption[4].  The eruption was most likely a 0 on the VEI index because the eruption was very small.  While the explosion did propel large lithics at least 50 meters from the summit, the eruption did not even produce any lava flows.  Since the lava of Ol Doinyo Lengai is the least viscous in the world, having a similar viscosity to water, the eruption could not have been very powerful.  Ol Doinyo Lengai is an anomaly, and thus does not fit into a classic Mercalli eruption style.  Because the volcano erupts frequently and emits effusive lava with low viscosity, the closest classification would be Hawaiian.  However, Ol Doinyo Lengai is a stratovolcano, having a drastically different topography than the shield volcanoes of normal Hawaiian eruptions.  Thus, Ol Doinyo Lengai defies the classifications of Mercalli, but if it must be grouped on that scale, then the volcano is closest to a Hawaiian eruption.