Mount St. Helens Volcano Updates:
August 18-23, 1982
Excerpt from:
Tilling, Topinka, Swanson, 1990,
Eruptions of Mount St. Helens: Past, Present, and Future:
USGS Special Interest Publication
|
|
Throughout the 1980s, the ability of scientists at
CVO and the University of Washington to provide
warnings for dome-building eruptive episodes has
been exceptional. Indeed, for all episodes (except
for one small event) since May 1980, scientists-
using data from seismic, ground deformation, and
volcanic gas monitoring-have provided reliable
forecasts from several hours to several days, even
weeks, in advance of these events. The table
gives a typical example of the timely information for
one 1982 eruption given to government officials
charged with emergency management and to the
general public via news releases.
At Mount St. Helens, the track record for predicting
eruptions, especially dome-building ones, is
better than any previously accomplished for any
volcano in the world. Our improving predictive ability,
however, has not been tested by any large explosive eruptions.
|
Mount St. Helens Volcano Updates: August 18-23, 1982
|
| Type of Notice and When Issued
|
Excerpt
|
| Extended Outlook Advisory: 1 p.m. July 30
|
"an eruption will probably begin within the next 3 weeks."
"...the eruption will consist primarily of dome growth."
|
| Advisory Update: 11:30 a.m., August 16
|
"eruption will begin within the next 4 days, possibly within 2 days ... the
eruption will consist primarily of dome growth, but as with all dome
growth, minor explosive activity is also possible."
|
| Eruption Alert: 6:55 a.m., August 17
|
"Seismicity and rates of deformation in the crater have accelerated sharply
... the expected eruption will probably begin within the next 24 hours."
|
| Updated Eruption Alert: 7:45 a.m. August 18
|
"The dome is already growing internally, but we have not seen any discrete
event yet, for example, an explosion, a change in the character of
seismicity or deformation ... or gas emissions, that in other eruptions
has signaled the onset of ... eruptions. We still expect lava to eventually
work its way through the dome and to be extruded as a new lobe on the
surface of the dome."
|
| Eruption Update: 7:15 p.m. August 18
|
"Lava finally broke through to the top of the dome this morning, and a
new lobe is flowing slowly onto the western and southern sides of the dome."
|
| End-of-eruption Advisory: 8:45 p.m., August 23
|
"Deformation and gas emissions have returned to their background levels,
so this eruption is essentially over. Minor sagging and spreading of the
new lobe may continue for a few days, accompanied by occasional rockfalls
and dust plumes."
|
|
