During this #First100Days post we show photography of how the land is still shaping from the May 18, 1980 eruption. Please share and enjoy todays post! May 21, 1980 3 days after the eruption Eruptive and seismic activity have continued to decline at Mount St. Helens, following the trend reported yesterday morning. Eruptive activity at the crater vent is now sporadic, and much of the emission appears to be condensed steam. It appears that the debris flow that rushed down the drainage of the North Toutle River on Sunday morning, immediately after the initial northward-directed blast, was relatively cool. It probably represents the remnant of the volcanos north flank that disappeared after the blast; the sporadic warm areas in it probably represent warmer parts of the volcanos interior before its disruption. This debris-flow deposit also contains blocks of ice from the north-flank glaciers that disappeared with that part of the volcano; some of the blocks have melted in place and leave holes in the hummocky surface of the debris flow. Temperatures were measured in secondary pyroclastic flows that formed from the ash of the initial blast deposit and are now as high as 295?F at depths of about 2 feet. The large fumaroles and secondary explosions that have disrupted the debris flow and younger pumiceous pyroclastic flows in the upper drainage of the North Toutle River may have their heat source in the hot ash of the initial blast deposit. Seismicity has declined dramatically and is lower than any time since March 22. There have been no earthquakes of magnitudes greater than 3 since 7:22 a.m. on Monday morning. All of the earthquakes of magnitudes greater than 1.5 are now occurring from depths greater than 6 miles. The principal immediate hazard potential remains the possible overflow of Spirit Lake, which could cause further mudflows and flooding the valley of the North Toutle. The best data available from observations and from radar imagery, although they are incomplete, do not suggest that the lake level is rising rapidly. From May 21 to May 25 the Yakima wastewater-treatment plant was out of operation due to ash plugging and damaging the pumps and filters. During this period the system was bypassed, and all sewage was divested directly to the Yakima River. Direct damage cost to the system was over $1 million.
Posted on: Wed, 21 May 2014 23:12:00 +0000
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