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Colima volcano (Mexico): July 2015 Montitlán pyroclastic flow deposit a year later

On 11 July 2015, a large dome collapse triggered the second largest block and ash pyroclastic flow of the 21st century (surpassed by Merapi in 2010 only), filling and devastating the Montitlán river valley on Colima's south side to a length of about 10 km.
We visited the deposit approx. 16 months later, in Nov 2016 (compare these to photos taken few days after it was deposited). This fresh, the deposit is a fantastic geologic showcase. It provides extremely interesting insights into the dynamics of this kind of pyroclastic density currents and its origin:
The pyroclastic flow deposit at the exit of the Montitlán ravine; its surface is still barren, but small fluvial channels have started to form. (Photo: Tom Pfeiffer)
The pyroclastic flow deposit at the exit of the Montitlán ravine; its surface is still barren, but s... [info]
(242 visti)
Large, partially burnt or charred tree trunks abound in the deposit, witness of the destructive power of the flow. (Photo: Tom Pfeiffer)
Large, partially burnt or charred tree trunks abound in the deposit, witness of the destructive powe... [info]
(236 visti)
View towards the volcano in the background, mostly hidden beneath its afternoon cloud (Photo: Tom Pfeiffer)
View towards the volcano in the background, mostly hidden beneath its afternoon cloud (Photo: Tom Pf... [info]
(195 visti)
View upstream of the flow deposit; Livio gives a scale. (Photo: Tom Pfeiffer)
View upstream of the flow deposit; Livio gives a scale. (Photo: Tom Pfeiffer) [info]
(198 visti)
After reaching the exit of the narrow gorge, the flow widened, surpassed the banks of the valley and inundated the flatter areas. Where the green bushes stand, a narrow stretch of surface was spared. (Photo: Tom Pfeiffer)
After reaching the exit of the narrow gorge, the flow widened, surpassed the banks of the valley and... [info]
(170 visti)
During transportation within the turbulent block and ash flow, the blocks constantly bounce against each other, leaving impressive scratch marks, sometimes deep dents several centimeters long. (Photo: Tom Pfeiffer)
During transportation within the turbulent block and ash flow, the blocks constantly bounce against ... [info]
(168 visti)
New life often starts at the dead wood pieces. (Photo: Tom Pfeiffer)
New life often starts at the dead wood pieces. (Photo: Tom Pfeiffer) [info]
(178 visti)
Heike, Ingrid and Livio examine the rocks left by the flow. (Photo: Tom Pfeiffer)
Heike, Ingrid and Livio examine the rocks left by the flow. (Photo: Tom Pfeiffer) [info]
(159 visti)
First plants manage to grow on the deposit after more than a year. (Photo: Tom Pfeiffer)
First plants manage to grow on the deposit after more than a year. (Photo: Tom Pfeiffer) [info]
(135 visti)
Close-up of a rock sample: a block of juvenile magma (from the dome or lava flow) made of blackish, glassy lava with a xenolith of lighter, more feldspar-rich lava which is presumably from an older batch of magma that had mingled with the younger (black) one; possibly a clue to the dynamics of the eruption? (Photo: Tom Pfeiffer)
Close-up of a rock sample: a block of juvenile magma (from the dome or lava flow) made of blackish, ... [info]
(144 visti)
As we visit the deposit, smaller rockfalls occur on the active lava flow from the volcano behind; their trajectory would be the same as past year, but fortunately, the volume and extrusion rate during Nov 2016 are much smaller and it seems unlikely (but not impossible) that a similar event occurs while we visit the area. Still, we're a little bit concerned. (Photo: Tom Pfeiffer)
As we visit the deposit, smaller rockfalls occur on the active lava flow from the volcano behind; th... [info]
(150 visti)
In the lower part of the deposit, where the flow was about to loose its energy, parts of the old ground of the previous river banks survived. (Photo: Tom Pfeiffer)
In the lower part of the deposit, where the flow was about to loose its energy, parts of the old gro... [info]
(128 visti)
The latest erosion allows to study fresh cross-sections of the pyroclastic flow deposit. (Photo: Tom Pfeiffer)
The latest erosion allows to study fresh cross-sections of the pyroclastic flow deposit. (Photo: Tom... [info]
(148 visti)
Livio standing on top of the deposit viewed from the new river channel. (Photo: Tom Pfeiffer)
Livio standing on top of the deposit viewed from the new river channel. (Photo: Tom Pfeiffer) [info]
(136 visti)
View of the fine-grained base layer of the block and ash flow (upper portion of section). (Photo: Tom Pfeiffer)
View of the fine-grained base layer of the block and ash flow (upper portion of section). (Photo: To... [info]
(136 visti)
The deposit is a chaotic mixture of fine gray ash with blocks and burned wood pieces. (Photo: Tom Pfeiffer)
The deposit is a chaotic mixture of fine gray ash with blocks and burned wood pieces. (Photo: Tom Pf... [info]
(136 visti)
 

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