30 Years After Mt. St. Helens Eruption, Active Volcanoes Still Threaten US

Mt. St Helens 188 years to the day after it was first seen by George Vancouver and one day before it blew apart

Numerous Active Volcanoes Along Northwest Coast of North America

On This Date in History:  When one thinks of volcanoes, typically one might have a vision of an island such as Hawaii or Iceland on which a mountain blows its top and all sorts of lava, steam and debris rises.  In the United States, most people are familiar with one of Hawaii’s volcanoes or perhaps a more astute observer would recognize Alaska’s numerous volcanic mountains.  Either way, we think of them as being far removed from most of America.  Yet, the Cascade Mountains feature a number of volcanoes.  Mt. Hood in Oregon makes the news most frequently as a peak on which hikers get stuck in blizzards every year with often tragic results.  But, it is an active volcano.  Mt. Baker in Washington is one of the snowiest locations on earth.  In fact, in 2005, Mt. Baker set the all time record for the most snowfall on record for any single point in recorded earth’s history.  It is an active volcano.  So are Mt. Adams and Glacier PeakMt. Ranier towers over Seattle providing a landscape on a clear day.  Mt. Ranier is an active volcano.  Perhaps the least known of the Cascade volcanoes is Glacier Peak.  The most well known Cascade Volcano is Mt. St. Helens.

Baron St. Helens

St. Helens got its name from HMS Discovery Commander George Vancouver who was on a survey mission of the Northern Pacific Coast from 1792 to 1794.  He named the mountain for British diplomat Alleyne Fitzherbert whose royal title was Baron St. Helens.  Indians in the region had told early explorers of a fiery peak that the Native Americans called Louwala-Clough, which means “smoking mountain.”  The story told was that the mountain was once a beautiful maiden named Louwit.  The Great Spirit Sahale had two sons who both fell in love with Louwit and she could not choose between them.  So, the two men did what men do when they both have their eye on the same girl: they fought.  Wyeast and Klickitat fought one another and buried villages and wiped out forests in the process.  Sahale got pretty miffed at the whole thing and struck down the love triangle.  Since Louwit was the most beautiful, she became a mountain with a symmetrical cone dressed in white.  Wyeast was transformed into a mountain that showed him lifting his head in pride.  Klickitat had wept when he saw Louwit wrapped in white and so he became a mountain with a bended head gazing longingly at Louwit.  These three mountains were St. Helens, Mt. Hood and Mt Adams respectively.  The legend says that both Klickitat and Wyeast continued to battle over Louwit even as mountains by tossing fiery rocks at one another and causing great earthquakes. 

St Helens Erupted Many Times in the 19th Century But Probably Nothing like that of the late 20th Century

On May 19, 1792 Louwit was first observed by George Vancouver while he was mapping out the Puget Sound inlets at Point Lawton.  Just 8 years later, an eruption of Mt. St. Helens was reported to explorers, missionaries and traders by numerous peoples, including the Sanpoil and Spokane Indians.  The Spokane chief told of the effects of the ash fallout.  Lewis and Clark spied the mountain from the Columbia River in 1805 and 1806, reporting no volcanic activity nor any evidence that suggested that there had been a major eruption in 1800.  But, the observations of quicksand and channel conditions they found at the mouth of the Sandy River indicates that there probably had been an eruption of Mt. Hood sometime in the previous 20 years.  Observations by several different people over time suggest that perhaps St. Helens erupted 1831, 1835 and 1842.  In 1847, a vent about half way down the north slope of Mt. St. Helens may have erupted.  This vent was the site of much activity and became known as Goat Rocks dome.  Other observations have led modern vulcanologists to believe that there were several small eruptions through 1857.   Other eruptions occured in 1898, 1903 and 1921, though these are thought to have been steam emmissions, large rockfalls or small explosions because deposits from these events were never found.

Biggest Landslide In Recorded History Cost St. Helens Over 1300 Feet of Height and Resulted in a lateral blast 1000 times more powerful than Hiroshima Atomic Bomb

For two months in 1980, earthquakes  and other seismic events suggested that the mountain was on the verge of another eruption.  In that time frame, 10,000 earthquakes were recorded as well as hundreds of steam blast explosions.  The north side of the mountain also bulged outward by about 80 meters(262 feet).  At 8:32AM on this date in 1980 the volcano was rocked by a  5.1 magnitude earthquake.  The shaking beneath the mountain caused the north face of the mountain to slide away in the largest landslide ever in recorded history. (Video of eruption) The loss of the north side of the mountain resulted in a devastating lateral blast of hot steam and ash to blow across the landscape at about 1100 kilometers per hour, or 682 miles per hour.  Temperatures soared to 300 degrees Celsius or about 572 degrees Fahrenheit.  At sea-level, the speed of sound is 761 mph.  But, the speed of sound is not a fixed constant but instead varies with temperature and altitude.  At an altitude of 10,000 feet and an air temperature of -4.8 C, the speed of sound is about 735 mph.  Now, if one considers that, prior to the eruption, St. Helens stood tall at 9677 feet above sea level, we might surmise that the speed of sound from the altitude of the blast was about 740 mph.  Hence, the explosion rocketed rock debris, ash, steam and just about anything else laterally at Mach .92.  It didn’ t need to break the sound barrier to cause utter destruction.  The shock wave flattened everything for miles.  A vulcanologist observer was standing on a ridge five miles from the summit.  His name was David A. Johnston.  188 years and one day after George Vancouver first observed Mt. St. Helens from Puget Sound, other observers heard Johnston cry out on his radio, “Vancouver! Vancouver! This is It!”  His moment of exhileration lasted but an instant as Johnston was blasted out of existence  at 8:32 AM on May 18, 1980.

The "Colorful" Harry Truman was Buried in Tons of Debris 90 seconds after St. Helens Blew Its Top

With all of the signs of an iminent eruption, authorities had ordered the evacuation of everyone around the mountain except for a few scientists.  Johnston was the closest.  But also there was an old man by the name of Harry Truman.  He was not the former president but instead was a local who lived on nearby Spirit Lake.  The media turned him into a folk hero with numerous reports focusing on his refusal to leave his home.  Presumably, the body of Harry Truman is forever entombed in his lodge below 150 feet of volcanic debris.  Spirit Lake was filled with felled trees.  In fact, trees were felled everywhere like pick up sticks from the blast while others were swept away when the snow almost instantaneous melted and a pyroclastic flow  of water, earth and rock raced down the mountain at about 600 mph.  Within minutes, a plume of ash rose to a height of 19 kilometers or 80,000 feet and carried 540 million tons of ash over 57,000 square kilometers of the Western US.  Contour maps would have to be changed because the 9764 foot mountain some called America’s Mount Fuji had been reduced to just 8364 feet.   The crater was 2100 feet deep. 

Giant Rockslab Protruding From Crater of Mt. St. Helens

Today, 30 years later, the mountain still smokes and steams now and again. Small earthquakes still rattle the region on a fairly regular basis.  When Snow White and I went there in 2005, there was a very tall protrusion from the center of the crater.  The Park Ranger told me that it was a rockslab column that grew many feet each day.  On that particular afternoon, she estimated that it was about 400 feet in height but was sure to soon break, only to be repeat the process of rising and breakage again over the next 24 to 48 hours.  I asked her if the dark material I could see from the Johnston Observatory, so named because of its location on the same ridge occupied by David Johnston when the volcano blew, was a bunch of old lava.  She said that it was in fact a glacier that had formed inside the crater that had turned black due to debris spewed out from time to time from small eruptions.  You see, St. Helens really didnt have much lava. 

Blast Zone of Devastation From Mount St. Helens

In about 180 seconds, Mt. St. Helens had flattened millions of douglas fir trees, killed 57 people and over 7000 big game animals as well as countless fish and birds.  3.7 billion tons of rock and soil was hurled over 230 square miles of pristine forest.  The Pacific Northwest is a subduction zone where a plate on the ocean floor sinks down underneath the North American plate.  As the ocean floor is forced down under the North American plate, magma rises to the surface, thus forming the Cascade Mountain Range.  Typically, this magma is filled with gas; much more gas than is often found in island chain volcanoes which is why the actual lava from St. Helens was minimal.  The rocks at the surface are very hard and not very pourous.   Expanding gas and magma built up below the mountain and went toward the path of least resistence.  That would be crevices and outlets carved out by previous eruptions.  I speculate that the weak point was the old Goat Rocks dome.  Scientists think that the stage may have been set from previous eruptions in the mid 1800’s.  When the earthquake occured, the weak point on the north face gave way releasing every bit of the built up pressure in one instant.   

Ash From St. Helens Fell on a large chunk of the US

In March of 1980 there was very little in the way of seismic activity.  It’s a bit unusual for a volcano to come to life in such a short period of time but, perhaps, rapid build up of pressure with very little in the way of release is what led to such a devastating eruption.  While there were 57 regrettable, but probaby preventable, loss of human life the eruption provided the science community and unique opportunity to try and study and understand volcanoes.  Mt. St. Helens eruption statistics can be mind boggling.  The wildlife loss was also heartbreaking but, within months, what had become a moonscape that people (the media) speculated would be lifeless for years actually began a rebirth.  Today, the forest is slowly regenerating.  About a quarter mile of the mountain was sheered away but it too is slowly rising again.  Someday, Mt. Ranier will explode and so will Mt. Hood.  Seattle would be devastated if Ranier were to suddenly awaken in a rage.  Should the brave Wyeast decide to throw a jealous fit, Mt. Hood could make a violent eruption that would threaten Portland. 

Small Eruptions Continue From Time to Time

And keep in mind that, while Mt. St. Helens was an explosion of epic proportions with an energy release of about 24 megatons (Hiroshima was about 10 to 20 kilotons) it is nowhere near the largest estimated volcanic explosion.  While the explosion of Mt. St. Helens was about 1000 times greater than the atomic bomb dropped on Hiroshima, the eruption of Krakatoa (Krakatau)  in 1883 produced an energy release of 200 megatons of TNT, or 10,000 times greater than Hiroshima and 10 times greater than that of St. Helens. 

Go see Seattle while you can and, when you do, go see St. Helens.  It is mesmerizing.

30 Day Rain Total Through May 16, 2010

Weather Bottom Line:  The period of unsettled weather will persist through the end of the week.  But, just in time for the weekend, we improve markedly with a lot of sunshine and temperatures soaring to the mid 80’s.  So, be patient…not much longer.  From the map above, one can tell that Kentucky and Tennessee has had enough rain for awhile over the past month.  At this point, however, more rain can be expected over the next 3 days with the severe threat very limited.


3 Responses

  1. put more things about mt st helens on here its so boring

  2. Scary.

  3. thanks!

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