In the last two decades we saw the disasters brought about by three major volcanic eruptions, Mt. St. Helens in 1980, Divino del Ruiz in 1983 and Mt. Pinatubo in 1991.There are lessons to be learned from these so we may be better prepared for Mt. Ranier.

Mt. St. Helens

Mt. St Helens is an active stratovolcano in Skamania County, Washington in the Pacific Northwest of the United States. The volcano is part of the Cascade Range which forms part of the Cascade Volcanic Arc (Mount St. Helens, (2008), para. 6-7). The Cascade Volcanic Arc is part of the Pacific Ring of Fire. The tectonic settings involved with Mt. St. Helens are the Juan de Fuca Plate, Pacific Plate and North American Plate (Howe and Kramer, (n.d.), illn.2).

Mt. St. Helens has had four major and catastrophic eruptions from the late 15th century to the present. The 1480 and 1482 eruptions were of greater magnitude compared to the May 18, 1980 destructive eruption. A third major eruption occurred in 1800. Several smaller eruptions documented are the November 22, 1842 eruption that emitted ash fall in the surrounding areas and those in 1898, 1903 and 1921 which emitted steam, small explosions and huge rockfall (Mount St. Helens, (2008), para. 31-33).

The catastrophic May 18, 1980 eruption of Mt. St. Helens begun with intense volcanic activity consisting of a series of earthquakes, steam explosions and the swelling of its north flank beginning in late March 1980. At 8:32 in the morning, a 5.1 magnitude earthquake rocked the area setting off the calamitous nine-hour continuous eruption. Seconds after the earthquake, the entire north flank of the volcano collapsed into a fast-travelling landslide bringing with it an explosion of hot gas, steam and large rocks. Snow that melted due to the heat from the volcano brought gushes of water and rocks to the lowlands. Ash spewed out by Mt. St. Helens reached a 57,000 square km. radius of Western United States and traces of it were felt around the world. Sporadic eruptions continued for the next three days (Mount St. Helens, (2008), para. 34-39).

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Major volcanic hazards from the 1980 Mt. St. Helens explosive eruption were earthquakes, fine volcanic ash, ash fall, lahar, pyroclastic flows, debris avalanches, landslides, direct blasts and pyroclastic surges (Riley, (n.d.), para. 2-5).

The 1980 eruption of Mt. St. Helens, the worst in U.S. history, was disastrous to the area. It devastated several hundreds of miles of timber, recreation and private land due to volume of volcanic debris and ash fall.  It destroyed several species of plant life and killed numerous animals. Almost sixty persons were found dead or are missing. Lahar flow rendered the shipping channel of the Columbia River impassable. The ash fall greatly interrupted and hampered travel and brought about widespread economic loss. The threat of floods increased with the erosion of stream beds due to the volcanic deposits (Howe and Kramer, (n.d.), para 4-6).

Nevado del Ruiz

Nevado del Ruiz is an active stratovolcano located on the border of Caldas and Tolima in Columbia. It lies within the Pacific Ring of Fire and is one of the volcanoes in the Andean Volcanic Chain of Western America. The tectonic settings for Nevado del Ruiz are the Nazca oceanic plate and the South American continental plate (How Volcanoes Works, (n.d.), para. 1-3).

Nevado del Ruiz is the second most active volcano in Columbia with several small eruptions in the past 700 years and three major eruptions occurring on1585, 1845 and 1985 (How Volcanoes Works, (n.d.), para. 1-3).  

The 1985 explosive eruption of Nevado del Ruiz is South America’s deadliest eruption.  Seismic unrest began in November 1984 with earthquakes and small eruptions. At 3:05 p.m. on November 13, 1985 there was a strong explosion of steam from the volcano. At 9:08 p.m. of the same day, a major eruption occurred bringing with it volcanic hazards such as ash fall, hot, fast moving pyroclastic flows and surge, lahar and mudslides down to surrounding rivers and six major valleys (Topinka, (2009), para. 3-5). In less than four hours, lahar flow into Armero killed three-fourths of its population. (Deadly Lahars from Nevado del Ruiz, 2009, para. 2-9).

The 1985 eruption of Divino del Ruiz was indeed a major disaster as it resulted in catastrophic loss of life and property. In its aftermath were buried towns, more than 23,000 dead in Armero alone, 15,000 livestock destroyed, a large number  of the population were injured and homeless.  The estimated damage brought about this disaster was One Billion US Dollars (How Volcanoes Works, (n.d.), para. 7-8).

Mt. Pinatubo

Mt. Pinatubo is an active stratovolcano located at the boundaries of the Pampanga, Tarlac and Zambales in Southern Luzon in the Philippines. Mt. Pinatubo is part of the Pacific Ring of Fire and the Philippine Fault Zone. It is part of the Luzon Volcanic Arc. The tectonic setting of Mt. Pinatubo is the Western Bataan Lineament (Topinka, (2009), para. 1-5).

Mt. Pinatubo has only had two known major catastrophic eruptions. One was about 35,000 years ago. Mt. Pinatubo then remained dormant for more than 500 years. The second devastating eruption was on June 15, 1991 making it the second most violent and destructive volcanic eruption in the 20th century (Rosenberg, (n.d.), para. 1).

The 7.7 magnitude earthquake of July 1990, with epicenter just 80 km. north-northeast of Mt. Pinatubo, appears to have awoken the long slumbering Mt. Pinatubo. In March 1991 a series of earthquakes, increasing in intensity and frequency, were felt on one side of the volcano. In April 1991, Mt. Pinatubo woke up with small eruptions causing ash fall and earthquakes in the surrounding areas. On June 7, 1991, Mt. Pinatubo spewed out lava and large amounts of ash. A series of explosive and violent eruptions began on June 12 and continued until June 14, 1991. On June 15, 1991 the most violent of these eruptions occurred at about 1:42 p.m. and continued for the next nine hours, sending out a massive amount of ash and sulphuric gas. Practically the entire Luzon was in darkness due to the ash fall. Together with this eruption, Typhoon Yunya added to the calamitous amount of tephra which increased the death toll (Rosenberg, (n.d.) para. 1-9).

The major volcanic hazards brought about by the 1991 eruption of Mt. Pinatubo were massive amounts of lahar, sulphuric gas, tephra, pyroclastic flows and earthquakes (Topinka, (2009), para. 4-10).

The 1991 Mt. Pinatubo eruption was seen as the most violent, destructive and devastating volcanic disaster of the 20th century. More than 800 people were dead, more than 100,000 homeless due to lahar flow and tephra which buried their homes. The 9-hour eruption caused an irreparable cooling effect to the earth by emitting a large amount of aerosols into the atmosphere, lowering the earth’s temperature by at least 1%. Billions in infrastructure, agriculture, livestock and property were destroyed. Air travel was severely hampered due to the heavy tephra which reached as far as Russia and North America. The health of millions of people was endangered due to the harmful effect of the ash fall. Staggering economic and social effects were felt by millions of people (Rosenberg, (n.d.) para. 8-13).

Mount Ranier

Mt. Ranier, a massive active stratovolcano, is located in the Mt. Ranier National Park, Pierce County in Washington U.S.A, southwest of Seattle-Tacoma. It belongs to the Cascade Volcanic Arc.  The tectonic setting for Mt. Ranier is between the Juan de Fuca and North American plates (Hoblitt et al, (1995), pp. 1).

Mt. Ranier is considered one of the most dangerous volcanoes in the world due to the large population in the areas surrounding it. The first eruption of this volcano is said to have occurred 500 million years ago. The latest eruption is said to have happened in 1894. Volcanic hazards known to be brought about by these eruptions were large amounts of lahar, pyroclastic flow and tephra (Hoblitt et al, (1995), pp. 1-6).

The nearness of Mt. Ranier to the suburbs of Seattle and Tacoma and the fact that it borders six counties makes it a significant danger in the region. In Pierce County alone, several organizations employing several thousands of people are located. The Port of Tacoma, the sixth largest container port in the U.S. located in Pierce County. Three military installations are found in Pierce County, Fort Lewis, McChord Air Force Base and Madigan army Medical Center.  Boing Company and Intel Corporation are also situated here. Millions of people’s lives will be in danger.  Mt. Ranier National Park, where Mt. Ranier is situated, is a popular recreational destination that receives almost 2 million visitors a year. So these densely populated areas make a major eruption of Mt. Ranier an extremely hazardous situation. Volcanic ash would pose damaging effects to health and agriculture.  Pyroclastic flow is estimated to affect all that is within park boundaries. The weightiest hazard is lahar flow that can cause extensive damage to human structures that will have major economic and social effects.

Washington disaster planning officials have been formulating a comprehensive strategy to prevent a major disaster from occurring in the event of a major Mt. Ranier eruption.  They have formulated and set up an alert warning system, through the  five permanent seismographic stations along the volcano, and evacuation plans; emergency response preparation-before, during and after volcanic hazards take place; extensive public education on disaster preparedness for volcanic activity and hazard maps, evacuations and hazards; appropriate alleviation procedures; and plans for post-incident recovery. They have limited property development in identified mountain hazard areas in and around the surrounding counties. Shelters have been identified. Effective communication equipment and a system of communication between local and federal agencies have been set up (Mt. Ranier: Volcanic Hazards Response Plan.

It is evident through the extensive plans and strategies formulated by the disaster planning officials of Washington, that careful examination of the signs, actual events and effects of the destructive eruptions of Mt. St Helens, Divino del Ruiz and Mt. Pinatubo were taken into serious consideration. The disaster preparedness plan they have come up with covers the major effects of volcanic hazards that occurred in these eruptions relative to that of Mt. Ranier.  They even have an automated lahar warning system, as lahar is the biggest threat to population and property in and around the area.  Heavy lahar flow may occur at any time even without an eruption due to the possible collapse of weakened parts of Mt. Ranier.

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