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

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. Example of Plinian Eruption pumice

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

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/