mow na loa isjust over 190 miles from the hawaiian state capital honolulu. the lava flow is mostly contained within the summit, but nearby residents have been placed on alert. scientists are warning the situation is volatile and could change rapidly. here s howard johnson. red warning. as mauna loa began spewing lava, the united states geological survey, or usgs, raised its alert level to the highest tier, indicating a major volcanic eruption is under way. it s the first time the world s largest active volcano has erupted since 1984. at the time, the lava came within eight kilometres of the city of hilo. but this time, it s not thought that the flow is life threatening. it s high on the flank of the volcano, so it s got a long way to travel before it reaches any population centres. and it s on one of the most gradual slopes.