Nevado del Ruiz, Columbia 1985
The Nevado del Ruiz is an active volcano in Columbia that is known for creating lahars. This is largely due the amount of snow on top of the mountain that is often melted in the event of an eruption. The melted snow creates lahars which move quickly down the mountain to devastating effect. In November 1984 geologists began noticing more seismic activity around the mountain. Then on September 11th, 1985 there was an ash ejection which was the biggest sign of an impending eruption. A study on October 22nd 1985 found the that risk of lahars from an eruption was very high and local authorities performed some preparedness techniques.
On November 13th, 1985 Nevado del Ruiz started to erupt and ejected 35 million tons of material, including magma. The pyroclastic flow rushed over the landscape and melted the glaciers and snow at the summit. This created four very large and thick lahars that began racing down the river valleys at the back of the volcano at a speed of 60km per hour. The lahars consisted of ice, water, pumice, rocks and clay and they eroded soil and dislodged rocks as they traveled. Once they reached the river valleys that led away from the volcano the lahars quadrupled in size with one reaching a width of 50 meters.
One lahar was particularly devastating to the town of Armero which was located in the Lagunilla River valley. The entire town was erased and three quarters of the town’s 28,700 residents perished. There was nothing left of the town. Another lahar hit the town of Chinchina and killed 1,800 people and destroying 400 homes. In total from all of the lahars more than 23,000 people died, 5,000 were wounded and more than 5,000 homes were destroyed. The lahar is the deadliest of recorded history, the worst natural disaster in Columbia’s history and the fourth deadliest volcanic eruption in recorded history.