Nevado Del Ruiz Eruption 1985

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/