Mt. St. Helens blows again


  • Anonymous


Mt. St. Helens Volcano, Cascade Range, southern Washington (46.20°N, 122.18°W). All times are local (GMT−8h). The first explosive eruption from Mt. St. Helens in 17 months ejected a tephra cloud that briefly rose to more than 13.5-km altitude on March 19. A directed blast from near the base of the lava dome spawned a multilobate avalanche that flowed several kilometers down the volcano's north flank. A mudflow moved down the north fork of the Toutle River but caused only minor damage. Clouds produced by explosions March 20–21 were much smaller and contained only a little tephra. Lava extrusion began March 21, adding a new lobe to the southeast side of the crater's composite dome. The eruption had been predicted by the USGS (see our report in last week's Eos) and no injuries resulted from it.