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Debris Flows

When creating this map, I used several different sources, including the preexisting, real hazard map released by the Observatorio Vulcanológico18 responsible for Colima, academic articles on Colima's behavior, and my own observations and conclusions, especially when determining where to place the lahar and pyroclastic flow-prone zones, as they were recognizable on Google Earth (as valleys). Cities were a little trickier to locate, and some have probably inadvertently been omitted, but the visible ones that were in obvious proximity to danger zones have been included, yet not identified.     Lahars – “A general term for a volcanic debris flow or, more generally, any rapidly flowing water-saturated mixture of rock debris and water from a volcano.” 11 How to make a lahar Tephra Mechanically weak rocks Water source Gravitational potential energy.15 Lahar is a fancy, foreign term for jokulhlaup, which is another fancy, unpronounceable, foreign term for rocks and ash and other volcanic material moving down a slope or through a valley or river.  Usually "lahar" is used to refer to the wet version of this event, and is thus commonly known as a mudflow.  The most common method of lahar production is rain. Lots and lots of rain. This can be a problem at Colima during the rainy season from June to October, as heavy rainfall can mobilized pyroclastic flow deposits down the volcano slopes and into rivers and valleys, traveling long distances, damaging infrastructures and affecting small villages along the banks or within valley walls.10 Lahars can also be produced by crater lake ruptures, temporary volcanic dams, and glacial water outburts. 10 Lahars are capable of moving swiftly, at varying speeds depending on their sediment and clast concentration in proportion to water, producing consistencies that could be as liquid as water or as thick as concrete. And not only do they carry fine particles of ash, but huge, meter-sized boulders may also be transported astonishing distances. According to N. Davila, et al. the greatest Potential for damage caused by this remobilization is at San Marcos, San Antonio, La Becerrera. 10   Pyroclastic Flows/Block-and-Ash Flows Glowing clouds, or nuees ardentes, just seems so much more pleasant than "pyroclastic flow" or "pyroclastic density current." Yet there isn't anything even remotely pleasant or romantic about a pyroclastic flow toppling over, scorching and/or incinerating every doomed structure, person, piece of vegetation, or hapless head of cattle in its path. These super-hot, super-fast flows of super-scariness can be formed by three mechanisms: Merapi Soufriere Column collapse12 And as we all know, a picture is worth a thousand words:   Fig. 4.4 Generation of pyroclastic flows The Basics: These flows generally follow topography, sticking to the valleys and ravines, so their potential paths are easy to predict. This means that particularly vulnerable areas include the ravines of Montegrande, La Lumbre, Cordobán, and La Arena 12 Block-and-ash deposits at Colima have been emplaced in drainages up to 6 kilometers from the vent due to the collapse of vulcanian eruptive columns, of summit domes, and of lava flow fronts 10. Pyroclastic flows typically flow less than 5 kilometers from the crater at Colima, but in October 2004, the longest flow partially filled La Lumbre over 6 kilometers 10.  Areas threatened by pyroclastic flows include: La Yerbabuena, La Becerrera, San Antonio, El Naranjal, Atenguillo, El Fresnal, San Marcos, Tonila, and Queseria12. Fig 4.5 Pyroclastic flow on Colima   Side-effects may include... Pyroclastic Surges – "Dilute and turbulent clouds capable of surmounting topographic barriers" approximately 500 meters from parent pyroclastic flow.  However, surges resulting from flows caused by avalanches could extend up to 1 km12. In other words, don't think you're safe and protected from hazards just because you're not in a valley or standing next to the crater.