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Andean Volcanic Belt
• Most northern Volcano on Andean Volcanic Belt
• Plate boundaries: – Nazca plate, – Antarctic plate, – South American
plate
Volcanic Belt
• Nazca Plate Subducts under S.A. Plate and Antarctic plate
• Contains active and dormant volcanoes
• High level of activity provides power and hot water to homes in the area.
Nevado Del Ruiz Volcano
• Stratovolcano• Active for nearly 2
million years• Composed of layered
lava – Alternating with hardend
volcanic ash and other pyroclastic rock
• Explosive eruption, high silica lava
Nevado Del Ruiz Mountain peak
Signs of Volcanic Activity
• Nov. 1984 signs of small earth quakes
• Fumarole that spew steam and gas were detected near the summit
• Sept 11, 1985 large ejection of ash from the peak of the volcano
• Nov 10, 1985 signs of magma movement and tremors
An Italian volcanological mission analyzed gas samples from fumaroles.They reported the risk of lahars to be very high
Example Fumardes
No Warning, No evacuation• Clear signs of an Active
Volcano – there was no evaluation
• Authorities would not take costly preventative measures to evacuate
• Last eruption over 140 years ago, – people thought there was
no danger• Armero's mayor and a
priest reassure city after an ash eruption– On the afternoon of
November 13•
Plinian eruption
• Type of Eruption that was produced on 1985
• Columns of volcanic ash and gas
• Ejection of pumice• Causes Lahars • Caused most of the damage
and death 1985 eruption.
pumice
Example of Plinian Eruption
Lahar
• Land flow or land slide, composed of pyroclastic material and water
• Buried the city• Caused by a small eruption• Deadliest lahar in recorded
history• Over 23,000 deaths
Armero in Colombia after the 1985 eruption
Eruption
• At 9:09 pm, on November 13, 1985• Total mass ejected: 35 million tons
– relatively small (3% of amount ejected from Mount St. Helens.)
Nevado Del Ruiz Caldera
Eruption continued
• Pyroclastic flow melted snow and glacier ice – Happened near summit, causing the Lahar
• virtually erased the small town of Armero, in the Lagunilla River valley
Impact to Armero
• At the time Armero's population was 28,700
• Over 23,000 were killed
• 5,000 were injured• 5,000 homes
destroyed
Aftermath Of Armero
Impact continued
• 2nd deadliest volcanic disaster in the 20th century
• The estimated cost of the disaster is $1,000,000,000
Sources
• http://www.geology.sdsu.edu/how_volcanoes_work/Nevado.html
• http://www.csmonitor.com/1985/1119/acolum.html
• http://vulcan.wr.usgs.gov/Volcanoes/Colombia/Ruiz/description_eruption_lahar_1985.html
• http://en.wikipedia.org/wiki/Nevado_del_Ruiz• Link to blog: http://armero1985.wordpress.com/