Saturday, November 24, 2012

More from the Sampling and Structural Mapping Ground Team

by Fabian Wadsworth
16th November 2012

We’ve returned from those first three nights among the domes of Santiaguito volcano. The November expedition was divided into a summit and a ground team. While the summit team camped at Santa Maria’s peak, peering cameras over the edge to look down on the Caliente vent, the ground teams hiked to the base of the domes and looked up. Those on the ground had many objectives, however, our contingent of the ground group was focussed on sample collection and structural mapping of the dome tops.
Yan Lavallée (University of Liverpool, U.K.) and Ben Kennedy (University of Canterbury, New Zealand) coordinated a sampling campaign with a two-fold focus. Yan and student, Adrian Hornby, aimed to collect homogenous material from the active Caliente vent to use for a variety of experimental applications such as high-velocity friction experiments, high-temperature rheology characterisation, and crack-propagation and healing. Ben and student Emma Rhodes were interested in mapping the volcano’s structural information among the spines of the three ancestral vents. Yan and Ben’s interests converge on the careful description and sampling of shear zones at the spine margins. It’s in these most-deformed areas that they find the field equivalent to the experimental products from the lab including evidence for both brittle and ductile deformation mechanisms and foamy inflation. Combined, these two complementary physical studies aim to constrain the evolution of Santiaguito’s magma properties over the course of the volcano’s activity; information that feeds into the deformation models used by the monitoring ground-team.
Students Adrian and Emma are resting in Xela city for now before rejoining the hunt for spines and bombs in the coming three weeks. Their task is a big one, not least because it takes the best part of a day to hike down to the dome valley floor and it’s a demanding job to mount and descend each dome, carrying equipment, water and food each time through the isolated valleys. Armando Pineda, the volcano-guide of Guatemala, will be an invaluable aid in their field research.
Corrado Cimarelli (LMU, Germany), a Santiaguito veteran from the January excursion, collected ash samples from individual explosions at the Caliente vent. He and his group in Munich will characterise variations and try to differentiate juvenile ash from fragmented dome ash, providing a window into conduit processes at Santiaguito. The multitude of tent tops made ideal ash-capture funnels for the frequent explosions and Corrado is now expert in gentle ash-sweeping actions using his personal make-up brush.  
The walk out from the domes was punctuated by a torrential downpour on the valleys surrounding the domes which mobilised rivers and lahars down the dome-flanks and over the trail. We stood at the top of the ascent out of the valley and saw our camp of the night before flooded before it disappeared in dense rain clouds.
We all relished our time at the domes and are grateful to the wider team for accommodating us. The interdisciplinary, international focus on Santiaguito volcano is a mighty undertaking that has such a broad, ambitious scope that I am sure it will yield collaborative research connections that continue over the coming years.
Thanks everyone.

Wednesday, November 21, 2012

Old School Volcanology

by Ben Kennedy and Emma Rhodes

We are oldschool physical volcanologists complete with hammers, compasses and maps, and we loved bashing rocks and getting covered in ash at Santiaguito. It felt a little like being trapped between the devil and deep blue sea with Santa Maria shedding rock falls on one side and Santiaguito chucking out pyroclastic flows on the other but we wouldn't have it any other way.  Emma will spend the next month climbing all over the Santiaguito dome to map the surface geological structures and internal textures of the lava. This should allow us to contrast the textures associated with lava, when it overtops the crater as a lava flow with when it pushes up a vertical spine of mostly solid lava. It is important to understand this transition in activity as vertical spines of lava are more likely to collapse to form large hazardous pyroclastic flows than long fluidal lava flows. Emma hopes to apply what she has learnt at Santiaguito to a lava flow from the recently active Te Maari vent at Tongariro, New Zealand. In addition, Ben collected bubbly bombs that he will cook in an oven at 1000°C to cause bubbles to grow and collapse in the molten rock. This growth and collapse of bubbles in magma is a possible explanation for some of the inflation and deflation events that other members of the team observe and record.

Beyond La Playona to Paradise

by Benjamin Phillips

The efforts of the dome teams, detailed in subsequent posts, were facilitated this trip by a new home base and campsite proximal to Caliente. Thanks to scouting by Jeff and Armando during a brief February reconnaissance, a team set course the morning of Sunday, November 11, for a veritable Paradise, as coined by Armando - a haven with a reliable source of fresh water nestled up against a stable portion of the Santa Maria scarp, and a mere few hundred meters from the base of the dome.

It is an arduous hike, especially when lugging heavy gear, that takes one through several phases and associated micro-environments - an initial ascent on open terrain past locals hauling large bundles of firewood that make one cringe; a short traverse to an overlook called Mirador and the first view of the older domes; the initial steep descent through a thicket of brush known as La Cicuta, overgrown to the point that being tall is a notable disadvantage; further descent of the smoothly polished lava of the Canaleta, where footing is always treacherous; successful arrival at the primary lahar channel of Santiaguito where climbing begins again, this time through a section along the margins of the domes aptly nicknamed the "Khumbu Rockfall"; arrival at La Playona, the moonscape at the foot of Caliente otherwise known as "The Moat," and site to January's seismo-acoustic-tilt stations; and finally the new traverse across two barrancas (drainage channels from Santa Maria) to Paradise. This sequence took the entire group about 8 hours. Not your typical work day.

A couple of highlights before I turn over the text to accounts from other participants. One was what a number of members of the team characterized as their most geophysically active hour ever. During a break in the shelter of one of the bus-sized boulders of La Playona, Caliente was as active as ever with explosions roughly every 20 minutes. One of these was accompanied by a large pyroclastic flow, a first for many of us. At 22:15 UTC (4:15 PM local time), a magnitude 6.5 aftershock to the November 7 M7.4 offshore Guatemala thrust event let loose about 30 km off the coast and rumbled through our rest stop, setting off an amplified barrage of rockfall down the scarp of Santa Maria. This was the largest quake since the primary rupture. Following this flurry of activity, the 45 minute traverse to Paradise, setting up camp, and enjoying a good meal, the team settled in for the night. There we were, camped in a rocky wasteland below the glowing inferno of Caliente, a setting that the non-enlightened might mistake for the other end of the world from paradise. But, this was clearly our own slice of heaven. The idyllic sound of the waterfall behind camp, punctuated by the regular rockfalls down Santa Maria and Caliente, was topped only by the deep roar of yet another eruption. What better to lull one's aching body to sleep!

Saturday, November 10, 2012

Return to Santiaguito, November 2012

by Benjamin Phillips

A new field campaign on Santiaguito begins tomorrow. A subset of the January team is back, supplemented by new faces. We were greeted in Xela today by a fiesta, including a death metal concert immediately outside the Hotel Modelo. Luckily, as of the writing of this post at 10pm the celebration has taken on a more subdued nature.

The focus this week is on imaging, sample collection, and mapping. Some will head first into the domes for two nights to test cameras and collect samples from below, while a small team will head straight to the summit to commence photogrammetry efforts. Look for an update later in the week.

November 2012 Santiaguito Team members:

Organized by
PI Jeffrey Johnson, Boise State, with student Brian Terbush

Dome imaging and sampling team
Corrado Cimarelli and Fabian Wadsworth, LMU Munich
Yan Lavallee, U. Liverpool, with student Adrian Hornby
Ben Kennedy, U. Canterbury, with student Emma Rhodes
Jake Anderson, New Mexico Tech
Danny Bowman, U. North Carolina
Lee Liberty, Boise State

Summit photogrammetry team
Ben Andrews, Smithsonian Institution, with student Ryan (U.T. Austin)

Documentation (and assisting with photogrammetry from the domes)
Ben Phillips, U.S. DOE / SRA Intl.

Logistical credit to
Armando Pineda, Mountain Guide