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e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
May 18, 1980, the day Mount St. Helens exploded: an amazing
story of destruction and recovery process of the environment
Arun KumarArun KumarArun KumarArun Kumar
“At exactly 8:33:00.5 a.m. on May 18, 1980, the north face of
Mount St. Helens fell away.” (Corcoran, 2005). This sentence
indicates as if some one was monitoring the time when this
volcano will erupt. Well, it was being monitored by David
Johnston, a geologist from the United States Geological Survey
(USGS), who sacrificed his life for the sake of enriching human
knowledge on volcanoes. David and 56 others perished under a
massive avalanche caused by an earthquake shortly after 8.32
a.m. (Corcoran, 2005). The Johnston Ridge Observatory near
this volcano is named after him. The enhanced intensity and
frequency of harmonic tremors around a volcano gives a clear
signal that it is going to erupt.
Mount St. Helens is located on the southern part of the Washington State in the USA. It is a
stratovolcano formed by several layers of ash, pumice and lava ejected by this volcano throughout its
history. This was a symmetrical volcano before May 18, 1980 (Figure 1) but became asymmetrical after
violent eruptions and massive land slide of the north flank (Figure 2). The current statistical details on its
morphology and subsequent changes during various volcanic activities are shown in Figure 3 and Table-
1.
May 18, 1980 Eruption of Mount St. Helens
On March 20, 1980 a 4.1 M earthquake shook Mount St. Helens, and a week later on March 27 a
column of steam and ash rose from its ice covered summit to a height of 7,000 feet with a loud bang.
The eruption and avalanches continued for days and a second crater appeared on the north flank that
later enlarged and merged with the original crater. By April 22 ash and steam eruptions had generally
stopped but harmonic tremors indicating the movement of the molten rock under the volcano continued.
The sound of cracking ground on the north flank was heard due to a “bulge” that was gradually forming.
By the end of April, 1980, this “bulge” grew to 1.25 mile long, 1.0 mile wide and 400 feet high, and it
was growing at the rate of around 5 feet per day. Thus, the north flank became more unstable by May 12
and a 5.0 M earthquake triggered a rock and ice avalanche that ran up to half a mile down. On May 18,
by 7.00 a.m. Mr. Johnston, who was located at the observation point Coldwater II, six miles northwest
of Mount St. Helens’ peak, had taken several measurements on the growing “bulge”. At about 8.32 a.m.
two geologists were flying over the volcano when a 5.1 M earthquake shook that created the massive
land slide. The already unstable north flank suddenly broke loose and skid downhill as a massive rock
avalanche. Ash rich eruption plumes rose from mid slope and from the summit crater. The two flying
geologists witnessed the erupted mass of hot gas, rock, ash and ice and safely landed but Mr. Johnston
could not escape incoming avalanche and perished under it. The following are some facts about this
eruption as described in Corcoran, 2005 and Volcano Review of April, 2007.
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
Figure 1: Mount St. Helens before May 18, 1980 from Spirit Lake on the north side. United States Forest Service
Photograph by Jim Nieland.
(http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/Images/MSH80_st_helens_spirit_lake_before_may_18_1980_med.jpg)
Figure 2: Mount St. Helens in June, 2010. Northern flank was removed on May 18, 1980. The author with his granddaughter
Shreya in the foreground.
1. In less than 10 minutes, the eruption leveled 230 squire miles of forest.
2. The mountain lost 1300 feet height and 0.67 3
miles of rock volume.
3. The area of new crater became 1.2 x 2.4 miles and 2,000 feet deep.
4. The eruption began with massive landslide (debris avalanche) that buried 14 miles of river valley
to an average depth of 150 feet.
5. The landslide released trapped magma and gas, producing a sideways explosion (lateral blast) of
hot rock and ash killing trees up to 17 miles north of the volcano.
6. Cement-like slurries of glacial melt water and boulders called lahars scoured and buried streams
draining the volcano.
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
7. A vertical ash eruption rose to a height of 15 miles above the crater and continued for nine hours.
Ash drifted to the east and northeast and traveled at least 950 miles.
8. Fiery avalanches of pumice and hot gases (pyroclastic flows) flowed into the valley north of the
crater.
9. 235 squire miles of land north of this volcano was devastated by hot volcanic debris.
10. Many miles of roads and number of bridges were destroyed.
11. A total of 57 people including the USGS geologist Mr. David Johnston died along with countless
numbers of wild animals.
Since May, 1980 the following volcanic activities and eruptions were recorded from Mount St.
Helens (modified from Volcano Review; April, 2007).
1980-1986: Episodic extrusions of lava built a large dome with in the crater.
September 23 - October 5, 2004: Large numbers of earthquakes occurred and after 18 years of quiet
period this volcano erupts once again. Steam and ash exploded and lava extrudes from crater floor at the
rate of one dump truck load per second and builds a new lava dome.
October 6, 2004 – March 31, 2005: Lava dome growth continues (half of a dump truck load per
second), small steam and dust eruptions.
October, 2006: Seven massive lava spines have been extruded (114 million cubic yards). At nearly
1400 feet, the top of the new lava dome is taller than the Empire State Building of New York (Figure 3).
May, 2007: Lava extrusion decreases (a small pickup truck load every two seconds). No explosive
eruption in a year. Dome rock falls and produced some small ash plumes.
Figure 3: Topographic profiles along a N-S axis through Mount St. Helens' crater. Profiles show geometry of new lava
dome relative to south crater rim, 1980 crater floor, 1980-1986 lava dome, and 2000 glacier surface. USGS Fact Sheet 2005-
3036; April, 2005. (http://pubs.usgs.gov/fs/2005/3036/fs2005-3036.html)
Origin of Mount St. Helens, the Cascade Range and the Pacific Ring of Fire
Mount St. Helens is one of several volcanoes of the Cascade Mountain Range. This range lies
100-150 miles east from the Pacific coast (Figure 4) and stretches for over 700 miles from Lassen Peak
in northern California and runs through Oregon and Washington in the USA and further north to the
Fraser River in southern British Columbia in Canada. Eruption history of the Cascade Range volcanoes
during past 4,000 years is given in figure 4 which shows that Mount St Helens has been the most active
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
volcano of this range. The volcanoes of the Cascades are called the High Cascades often standing twice
the height of the nearby mountains. Cascade Mountains began to rise seven million years ago in the
Pliocene. The Columbia River Gorge breaks this mountain range. This gorge was formed due to down
cutting of the rising mountain by the Columbia River. This is 4,000 Feet deep, is located along the
Washington-Oregon border and exposes uplifted and warped layers of basalt from the Columbia River
Basalt Plateau. Because of the range's proximity to the Pacific Ocean substantial amount of rain falls on
the western slopes than eastern side.
Figure 4: The volcanoes of the Cascade range and their eruption history for the past 4 K yr. St. Helens has been the most
active volcano of this region. (http://en.wikipedia.org/wiki/File:Cascade_eruptions_in_the_last_4000_years.png)
Figure 5: Distribution of tectonic plates on Earth. These plates are of different sizes and shapes. Red arrows indicate their
relative movement. Note the location of a small Juan de Fuca plate off west coast of North America.
(http://en.wikipedia.org/wiki/Pacific_Ring_of_Fire)
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
The origin of Mount St. Helens, like other volcanoes of the Cascade Range is related to the
constant movement of several large and small tectonic plates that cover the Earth (Figure 5) and the
geodynamic processes that control the movement of these plates is known among geologists as “Plate
Tectonics”. These are lithospheric plates (the outer layer of the earth) and ride on the asthenosphere.
There are three types of plate boundaries defined by their motion in relation to each other. First the
“divergent boundary”, where plates are moving away from each other like the boundary between the
North American Plate and the Eurasian Plate making the Mid Atlantic Ridge. Second the “convergent
boundary”, where two plates are moving towards each other and one subducts under the other forming
mountain ranges and volcanic arcs, for example, the boundary between the Indian plate and the Eurasian
plate where Indian plate has subducted under the Eurasian plate forming the Himalayan Mountain
ranges. Third the “transform boundary” when two plates move laterally against each other like San
Andreas fault of California (Figure 5). Earthquakes, volcanic activity, mountain-building, and oceanic
trenches form along the plate boundaries. The lateral relative movement of the plates varies typically
ranging from no movement to 100 mm annually. These plates move because the Earth's lithosphere has
lower density than the underlying asthenosphere and are driven by the motion of hot material in the
mantle and lateral density variations that result in convection.
Figure 6: Detailed structure and movement along the
eastern and western boundary of the Juan de Fuca Plate.
The cross section along the points A and B shows how
this plate is subducting under the North American Plate
which melts and forms magma that erupts as volcanoes
and this movement is also responsible for the formation
of Casacade Range.
(http://en.wikipedia.org/wiki/File:Cascade_Range_related
_plate_tectonics-en.svg)
Figure 7: Plate tectonic relationship showing relative
movement of the Pacific Plate, Juan de Fuca Plate resulting in
generation of Earthquakes and volcanoes of the Cascadia
Range.
(http://en.wikipedia.org/wiki/File:Cascadia_earthquake_source
s.png)
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
Juan de Fuca is a small plate on the western margin of the North American continent (Figure 5,
6). On its eastern margin it is subducting under the North American Plate (Cascadia Subduction Zone)
causing the rise of the Cascade Mountain ranges, responsible for all its volcanic activities and
earthquakes in the region (Figures 4, 7). The western margin of the plate is a faulted divergent boundary
(Juan de Fuca Spreading Zone) forming a spreading center. Thus it is pushing westward in the Pacific
Plate and subducting eastward under the North American Plate (Figures 6, 7).
The Cascadia Range is part of the ‘Pacific Ring of Fire’. It is a series of geotectonic features like
mountains, valleys, volcanoes, oceanic trenches and volcanic arcs that encircles the Pacific Ocean
(Figure 8). In the scientific literature this feature is also known as ‘circum-Pacific seismic belt’, is
around 40,000 km long and has over 452 (over 75 % of all volcanoes) active or dormant volcanoes of
the Earth. The regions covered by the ‘Pacific Ring of Fire’ are seismically very active where about 80
% of world’s largest earthquakes occur.
Figure 8: The “Ring of Fire” showing the location of Mount St. Helens and several trenches.
(http://en.wikipedia.org/wiki/File:Pacific_Ring_of_Fire.svg)
Figure 9: Hazards associated with stratovolcano eruptions. Not all hazards shown will accompany a single eruption,
although a single eruption can produce more than one type of hazard at the same time.
(http://gsc.nrcan.gc.ca/volcanoes/images/fig32_e.jpg)
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
Environmental Destruction and Recovery
Figure 9 shows the types of hazards a volcanic eruption poses to the environment, although a
single event might not cause all the hazards shown in the figure but in most cases few such hazards can
result from a single eruption. The May 18, 1980 eruption destroyed over 200 2 miles of forest in a 180
0
north of the volcano. Prior to the May 18, 1980 catastrophic event this area was thickly forested by
hemlock, and evergreen trees like Pacific silver fir, Douglas fir and many more species of plants (Figure
1). In these forests lived black-tailed deer, and Roosevelt elk, mountain goats and black bears. A lot of
species of small animals, bees and birds also inhabited these forests. Streams and rives of the area had
abundant ocean-migrating salmon and resident trout, likewise lakes and ponds too were teaming with
diverse forms of life including fishes and frogs. The May 18 event destroyed almost all of this, although
the degree of destruction varied depending on the distance from the volcano and direction of the
movement of pyroclastic flow, north-facing orientation, remaining snow pack, and sheltering ridges and
hills. Figure 10 show the logs of dead trees some of which have been cut probably for local use only.
Figure 10: Massive loss or forests after May 18, 1980
eruption of Mount St. Helens. Several dead trees have been
cut. Photograph by Paresh Maisuraia.
Figure 11: Massive loss or forests after May 18,1980
eruption of Mount St. Helens. See dead trees all over the
hills. This image shows regeneration of new trees in the area.
Photograph by Paresh Maisuria.
After the devastation, it took few months for some forms of life to come back and initiate the
process of re-colonization of the region. As rainfall and melting snow and ice removed ash and pumice
exposing the rich pre-eruption soil, the process of plant re-growth began. Ferns, berries and flowers were
observed in the shelter of dead trees. Even the decaying carcasses of animals were supporting plant life.
The miraculous tenacity of life is exemplified by a bacterium called Archaean bacteria initially reported
from the deep volcanic vents on the sea floor of the Pacific Ocean, was observed in the steam vents and
thermal springs near the lava dome at Mount St. Helens. It is an extreme example of life that
successfully survives high pressures, boiling temperatures and anoxic environments.
As the time goes on lakes and streams have become clear enough to support fish, plants are
growing in most places and gradually transforming grey landscape to green (Figure 11). Since grasses
and other plants are re-colonizing, gradually animals too are coming back because food is available for
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
them. By this time most of animals native to this region are back and life is thriving once again though
no where close to the pre- 1980 eruption environment.
Table 1: Statistical summary of the volcano, lava dome and the glacier dimension 1980-2005 USGS
Fact Sheet 2005-3036; April, 2005. (http://pubs.usgs.gov/fs/2005/3036/fs2005-3036.html)
Summary of volcano, lava dome, and glacier dimensions 1980-2005
Volcano
Elevation of summit 9,677 feet before 1980; 8,363 after; 1,314 feet
removed
Volume removed by May 18, 1980, eruption 0.67 cubic miles (3.7 billion cubic yards)
Crater dimensions 1.2 miles (east-west); 1.8 miles (north-south);
2, 084 feet deep
Crater floor elevation 6,279 feet
Crater glacier area (September 2000) 0.4 square miles
Crater glacier ice volume (September 2000) 105 million cubic yards
Maximum glacier thickness (September 2000) 650 feet
1980-1986 Lava Dome
Elevation of top of dome 7,155 feet
Height 876 feet above 1980 crater floor
Diameter About 3,500 feet
Volume 97 million cubic yards
2004-2005 Lava Dome (as of February 1, 2005)
Elevation of top of dome 7,642 feet
Height 1,363 feet above 1980 crater floor; 700 feet
above 2000 glacier surface
Dimensions of "whaleback" About 1,550 feet long, 500 feet wide
Diameter of lava dome and welt deformed by magma
intrusion, excluding deformed east glacier arm
About 1,700 feet
Volume of lava dome and welt defomred by magma
intrusion, including deformed east glacier arm
50 million cubic yards
Approximate percentage of crater glacier ice
removed
5% to 10%
Acknowledgements: I thank my son Anshuman and his wife Smita of Ottawa and daughter Anita and her husband Paresh of
Seattle for taking me to British Columbia (Canada), Washington and Oregon (USA). This region probably is the most
beautiful part of the Earth. In June, 2010 we visited national parks, beaches, volcanoes, and water falls and hiked through
lovely temperate rain forests. My baby grand daughter Shreya made this trip especially memorable.
Suggested Readings:
General information written in this article was taken from the following publications.
Corcoran, T. 2005. Mount St. Helens: The Story behind the scenery. K C Publications, Inc.
Volcano Review, April 2007. A publication of the Northwest Interpretive Association in cooperation with the USDA Forest
service. About the Author
Dr. Arun Kumar is a Research Scientist and Professor at the Center for Petroleum and Minerals, Research Institute, King
Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia. He obtained his Ph.D. (Stratigraphic Palynology)
from Michigan State University, USA and a second Ph.D. (Environmental Micropalaeontology) from Carleton University,
Canada. Dr. Kumar taught geology at Kumaun University, Nainital, India, University of the West Indies, Kingston,
Jamaica, Carleton University and Concordia University (Montreal) in Canada. He also worked as a geologist and
e-Journal Earth Science India: www.earthscienceindia.info Popular Issue, October, 2010
palynologist with Oil and Natural Gas Corporation of India and Core Laboratories International (USA) in Singapore and
Jakarta, Indonesia. His new research interest is in natural hazards and environmental issues.