Wednesday, March 31, 2010

Pre-Eruption St Helens Chronology

From the NW, March 30, 1980 (USGS photo archive), showing the summit graben, the north-side bulge, and an on-going steam eruption. Note the dark gray pulverized rock falling on the south side of the mountain. Below, an annotated version of the photo: north and west sides of the mountain are marked; a curved arrow shows the continuing movement of the the north side bulge; dotted lines show the approximate edges of the summit graben; double-headed arrow illustrates extension across the graben.I actually was not intending to post one of these retrospectives today, but I found a great resource I just have to share with anyone else who might be interested: The Mount St. Helens National Volcanic Monument has a terrific day-by-day chronology of the events leading up to the May 18 eruption... sort of like what I was aiming to do with these pieces, but better researched! Here's the front page, here's the section with today's entry, and here's today's entry:
March 31 - Both craters enlarged as explosions continued. A change in wind direction brought ash to the Kelso-Longview area by noon. To date none of the ash from these explosions has come from new magma, but rather pulverized bits of older rocks that make up the summit.

The frequency of earthquakes has decreased but the number of larger earthquakes has increased, so the total energy release remained about the same. Among these were two earthquakes of magnitude 4.6. Explosions and earthquakes triggered two avalanches of snow and rock near the Goat Rocks dome.

Cowlitz County Commisioners declared a state of emergency in an attempt to obtain assistance from the Washington National Guard in staffing roadblocks. According to a report in the Longview Daily News, Colonel Val E. McCreary (commander of the WA National Guard) announced that 300 troops, 50 trucks and 3 helicopters were on standby in case Governor Ray ordered evacuations.

The Washington Department of Emergency Services (WADES) pressed the Clark County Amateur Radio Club into service as a backup communications network should the primary network maintained by the USFS fail.

Public response to the activity varied. The Vancouver Columbian reported that USFS personnel had fielded calls from frustrated citizens who could not access their cabins within closed areas while members of the press had been allowed in.

Other calls ranged from gamblers requesting the number of explosions in the previous 24 hours to those blaming the volcano's restlessness on the desecration of Indian graves in the area.

Harry Truman began his climb to media folk-hero status due to extensive coverage in newspapers and television. He is the only person who has refused to leave his home on the south shore of Spirit Lake.

A Longview Daily News article quoted Harry as saying, "I think the whole damn thing is overexaggerated ... Spirit Lake and Mount St. Helens are my life ... You couldn't pull me out with a mule team."

I did and do have very mixed feelings about Harry Truman, but I'll save them for another post. I was trying to figure out when the first juvenile lava was detected in an eruption, as opposed to pre-existing powdered rocks. I seem to remember that brand new lava was detected before the big eruption, though I haven't found confirmation of that yet. It may very well be noted in the chronology above, but I was so thrilled to find it that I've only read the block quoted section above.

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