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]
(254 Éxitos)
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]
(247 Éxitos)
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]
(203 Éxitos)
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]
(200 Éxitos)
A smaller part of the flow traveled through a parallel side valley. (Photo: Tom Pfeiffer)
A smaller part of the flow traveled through a parallel side valley. (Photo: Tom Pfeiffer) [info]
(184 Éxitos)
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]
(175 Éxitos)
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]
(178 Éxitos)
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]
(183 Éxitos)
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]
(165 Éxitos)
Some of the blocks are several meters accross,- once pieces of the lava dome on top of the volcano. (Photo: Tom Pfeiffer)
Some of the blocks are several meters accross,- once pieces of the lava dome on top of the volcano. ... [info]
(158 Éxitos)
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]
(138 Éxitos)
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]
(155 Éxitos)
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]
(158 Éxitos)
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]
(137 Éxitos)
Rainfalls, in particular heavy ones, have started to re-excavate the river valley in more or less the same place as before. (Photo: Tom Pfeiffer)
Rainfalls, in particular heavy ones, have started to re-excavate the river valley in more or less th... [info]
(145 Éxitos)
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]
(158 Éxitos)
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]
(141 Éxitos)
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]
(141 Éxitos)
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]
(141 Éxitos)
The furthest tongue of the flow, at approx. 10 km distance from its source. (Photo: Tom Pfeiffer)
The furthest tongue of the flow, at approx. 10 km distance from its source. (Photo: Tom Pfeiffer) [info]
(138 Éxitos)
A large pine tree fell victim as it stood at the very edge of the flow. (Photo: Tom Pfeiffer)
A large pine tree fell victim as it stood at the very edge of the flow. (Photo: Tom Pfeiffer) [info]
(145 Éxitos)
Despite the intense heat of the ash at the moment it arrived (several hundred C), the tree didn't burn, but the heat dried it out completely, killing all life inside. (Photo: Tom Pfeiffer)
Despite the intense heat of the ash at the moment it arrived (several hundred C), the tree didn't bu... [info]
(131 Éxitos)
Dried-out pine cones still hang in on the dead branches. (Photo: Tom Pfeiffer)
Dried-out pine cones still hang in on the dead branches. (Photo: Tom Pfeiffer) [info]
(125 Éxitos)
The death of the tree became source of life in turn: its needles and hundreds of pine cones fell on the surface of the ash, providing the small extra layer of nutrients and protection to speed up re-growth of new vegetation considerably in this place, compared to the barren surface around. (Photo: Tom Pfeiffer)
The death of the tree became source of life in turn: its needles and hundreds of pine cones fell on ... [info]
(143 Éxitos)
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