Lahars contribute to some of the worlds deadliest and worst natural disasters in history. A lahar destroys anything in it’s path and can have an extremely devastiating outcome.
A lahar is a volcanic mudslide or landslide that is made up of pyroclastic material and water. It usually occurs and travels along a river bank or valley. It can happen suddenly and without warning.
Pyroclastic material or tephra is compsoed of fragments o pr-existing rock, ash, lapilli, bombs, and shatterd country rock. Lapilli are little rocks of molten or semi-molten lava that was thrown form the pyroclastic material. Bombs are big rocks of lava.
Once the material mixes with water it begins to travel with speed and energy. Pyroclastic material can melt ice ans snow in large quantities in a few hours time which can generate a lahar. Lahars can travel for many kilometers at dozens of millimeters per second. Like many types of mudslides, lahare are highly destructive and kill.
Although a lahar could easily be caused by volcanic erupiton, it is a myth that volcanic activity need be present in order to create a lahar. Lahars can be formed as long as the atmosphere, such as after a large amont of rain falls, allow the collapse of mud and ash to mix with water and create mud flow. The mixure of the volacanic tephra and the water is equal to the characteristics of concrete mixture. When the mudflow stops, it hardens just as concrete would.
Lahars that are caused by volcanic eruption happen because lava flow can easily melt glaciers causing basal glacier melting. The melting of glaciers allow water to mix with the tephra causing enormous and very dangerous lahars.
The temperature of a lahar can vary. It can be hot or cold, and vary between the two depending on it’s original source or cause of the lahar. Lahars can reach temperatures of up to 100 degrees Centigrade, which is the temperature at which water begins to boil.
The deadliest most dangerous lahar occurred in 1985, after the eruption of the volcano Nevado del Ruiz. Also known as Mount Ruiz, which is located in Colombia. Armero is a small town that is located near the volcano and abou 80 miles West of Bogota.
Nevado del Ruiz was named “the Sleeping Lion” due to it’sinactivity for over 100 years. On November 3, 1985 at exactly 9:08 p.m. Nevado del ruiz erupted. This errution occurred because, long lasting earthquakes had occurred recently in just the previous hours before the eruption. The earthquake caused the eruption and the eruption caused a lahar.
The material that came out of the volcano was said to have had high amounts of sulfur dioxide. Four thick, six inch deep lahars that were 50 kilometer in length formed and flowed quickly down the river valleys. The mudslide had flowed more than 100 kilometers.
The town of Armero was completely engulfed by this horrendous mudslide. 13 other villages were also tragically destroyed by the overwhelming lahars. In the town or Armero, 21,000 people lost their lives that day due this unstopplable, unpredictable natural disaster.
With an estimated 23,000 deaths, 5,000 injured, and 5,000 homes and 14 towns destroyed, the “Sleeping Lion” had awaken and left it’s name in the record book for the deadliest lahar in world history, as well as the worst natural disaster Columbia has ever faced.