Narrator: The May 18,
1980 eruption of Mount St. Helens was a seminal moment for volcanology
On that fateful morning, an earthquake and giant landslide
uncorked a lateral blast that flattened 230 square miles...
in a matter of minutes.
For nine hours after that, a vigorous eruption column
billowed into the atmosphere coating everything downwind
with ash. Local rivers were inundated by mudflows and debris
flows that took out bridges and homes for miles downstream.
For two months prior to May 18, 1980 scientists with the
U.S. Geological Survey and the University of Washington’s
Pacific Northwest Seismographic Network were closely
monitoring Mount St. Helens.
C. Dan Miller: But it was truly
only the beginning of an eruptive episode that
lasted for over 6 years. So the first explosion occurred
on May 18 and then there were several sizeable explosions in
the summer of 1980 and they sort of trailed off until
October of 1980 and then for the next five years or five and
a half years there were a series of dome building eruptions
in which molten material came out, very viscous pasty lava
come out on the floor of the crater and piled up to form a
dome or a mound in the middle of the crater floor a feature
that’s now about 900 feet high sitting on the floor of the crater.
So, this episode at Mount St. Helens which began on May 18
actually culminated in October of 1986 when the last magma
came out of the ground.
Narrator The volcano
reawakened again in 2004 displaying another period of dome building and smaller explosive eruptions.
This resumed unrest was an opportunity for the scientists
to deploy new and improved monitoring equipment.
Dan Dzurisin Today we deployed
with a helicopter a multi-sensor instrument
package that was developed literally in the past week or at least
fabricated in the past week at the Cascades Volcano Observatory.
This was in response to what we’ve been learning at the volcano
over the past two and a half to three weeks. The first thing we
did was deploy ground deformation instruments
out on the outer flanks of the volcano and learned that
they weren’t moving. Then last week we deployed three GPS
instruments on the old part of the lava dome itself.
And discovered that it’s moving very little if at all at the
same time that the feature on the south crater floor is moving
by tens of meters and so we wanted to get instruments directly
on the part of the dome that’s moving so dramatically.
And so we very quickly put together a GPS sensor, a seismometer,
a tilt meter and a microphone, the microphone will record the
sound of explosions should they occur and that’s important if they
occur in the middle of night or in bad weather we’ll have some indication
that that’s what's happened and integrate that into our data stream.
We’d like to know for example is the deformation continuing?
Is the rate increasing or decreasing? How does the rate
correlate with seismic activity? When we’re having more
earthquakes is the ground deforming more rapidly or less
rapidly because it’s easier for magma to move up the pipe?
And therefore producing fewer earthquakes. We don’t know
such fundamental things. And understanding those kinds of
relationships is key to trying to interpret the processes that
are going on understanding where the volcano might be headed
and therefore mitigating any hazards associated with future activity.
Narrator: Volcano
science and volcano monitoring have developed
impressively since May 18, 1980. Technology such as GPS,
infrared imaging, acoustic flow sensors and Dopler Radar
are just a few of the new tools available to the scientists.
They are studying hazards from lava flows to explosive
eruptions, mud flows, debris flows, debris avalanches and
airborne volcanic ash. The realization that volcanic ash can
stall a jet engine adds urgency to monitoring explosive
eruptions and any ash clouds that may threaten aircraft.
In the US and its territories there are 169 volcanoes capable
of erupting. With responsibility for monitoring these
volcanoes the USGS now operates volcano observatories focused
on Hawaii, Alaska, The Cascades, Yellowstone and
Long Valley in California. One important aspect of this
operation is the Volcano Disaster Assistance Program (VDAP)...
a team of scientists with a cache of monitoring gear that
responds to volcanic unrest across the planet.
Among the VDAP success stories was the forecasting of the
1991 Mt. Pinatubo, Philippines eruption in time to save
thousands of lives and to evacuate planes and people from
US run Clark Air Base.
Awe inspiring, spectacular and scary all characterize the
eruption of Mount St. Helens on May 18, 1980.
The human response to this catastrophic event has laid the
groundwork for saving lives and better addressing future
volcanic eruptions wherever they might occur.