Definition
Lahars also called mudflows contain fusion of water and consolidated particles of gravel, ice, wood, and other fragments that flow from volcanoes are distinct, prompt, and gravity-induced outflows of drenched, high-consolidation mixtures.(Vallance, 2000)
Types
Primary lahars
These are generated amidst outbursts by numerous eruption-related activities. Such lahars wiped out almost 37,451 people all over the world between AD 1600 and 2010. The Nevado del Ruiz disaster in 1985 caused death of 23,080 people .(Witham,2005;Aucker et al,2013)
Secondary Lahars
These are most commonly generated by post-outburst erosion and entrapment of rock fragments during heavy precipitation. It wiped out additional 6,801 people. (Aucker et al,2013)
Characteristics …show more content…
Hyperconcentrated flows: These have the consistency of flowy semi liquid mixtures of mostly mud and sand that look like motor oil.
Speed: Large lahars mostly achieve speeds of 20 m/s on the lower sides of volcanoes and more than 10 m/s for areas 50 km away from the source when restricted to narrowed canyons. (Cummans, 1981; Pierson, 1985; Pierson et al, 1990)
Temperature: lahar reaches the temperature of 100 degree Celsius and then dries out like concrete.
Effects:
Buildings, bridges, roads, farm lands or anything that comes in the way of lahar gets buried under lahar which dries out into cement like debris layer. Many fresh lahars remain flowy like quicksand for weeks which then complicate rescue operations.
People get trapped in areas where lahars are too deep, too soft or too hot. (Pierson et al, 2014)
Causes:
Most of the lahars are generated amidst or soon after volcanic eruptions, they can also start off by noneruptive events like gravitational collapse of weak volcanic structures, high intensity earthquakes, lake outbreaks, or extreme precipitation without any prior warning. (Pierson et al, 2015)
Mitigation
Lahars also called mudflows contain fusion of water and consolidated particles of gravel, ice, wood, and other fragments that flow from volcanoes are distinct, prompt, and gravity-induced outflows of drenched, high-consolidation mixtures.(Vallance, 2000)
Types
Primary lahars
These are generated amidst outbursts by numerous eruption-related activities. Such lahars wiped out almost 37,451 people all over the world between AD 1600 and 2010. The Nevado del Ruiz disaster in 1985 caused death of 23,080 people .(Witham,2005;Aucker et al,2013)
Secondary Lahars
These are most commonly generated by post-outburst erosion and entrapment of rock fragments during heavy precipitation. It wiped out additional 6,801 people. (Aucker et al,2013)
Characteristics …show more content…
Hyperconcentrated flows: These have the consistency of flowy semi liquid mixtures of mostly mud and sand that look like motor oil.
Speed: Large lahars mostly achieve speeds of 20 m/s on the lower sides of volcanoes and more than 10 m/s for areas 50 km away from the source when restricted to narrowed canyons. (Cummans, 1981; Pierson, 1985; Pierson et al, 1990)
Temperature: lahar reaches the temperature of 100 degree Celsius and then dries out like concrete.
Effects:
Buildings, bridges, roads, farm lands or anything that comes in the way of lahar gets buried under lahar which dries out into cement like debris layer. Many fresh lahars remain flowy like quicksand for weeks which then complicate rescue operations.
People get trapped in areas where lahars are too deep, too soft or too hot. (Pierson et al, 2014)
Causes:
Most of the lahars are generated amidst or soon after volcanic eruptions, they can also start off by noneruptive events like gravitational collapse of weak volcanic structures, high intensity earthquakes, lake outbreaks, or extreme precipitation without any prior warning. (Pierson et al, 2015)
Mitigation