1. Nevado Del Ruiz Eruption 1985

2. Andean Volcanic Belt Most northern Volcano on Andean Volcanic Belt
Plate boundaries:
Nazca plate,
Antarctic plate,
South American plate

3. 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.

4. 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

5. Signs of Volcanic Activity
Nov 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
Example Fumardes
An Italian volcanological mission
analyzed gas samples from fumaroles.
They reported the risk of lahars to be very high

6. 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

7. 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.
Example of Plinian Eruption
pumice

8. Armero in Colombia after the 1985 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

9. 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

10. 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

11. 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

12. Impact continued 2nd deadliest volcanic disaster in the 20th century
The estimated cost of the disaster is $1,000,000,000

13. Sources http://www.geology.sdsu.edu/how_volcanoes_work/Nevado.html
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