Current Research .....
Figure 1. Geographic locality of Lago de Atitlán.
2002-Present:
Graduate Research, Michigan Technological University, Houghton, MI
Field-hazard reconnaissance included geological hazard mapping of lahar,
pyroclastic flows and surges, lava, debris avalanche and tephra fall of
Atitlán Volcano. In conjunction with USGS Volcano Disaster
Assistance Program prepared a preliminary hazard report and the accompanying
maps.
Abstract of Current Hazard Research:
Volcanic Hazards at Atitlán Volcano, Guatemala
Atitlán Volcano is part of the Guatemalan Highlands, a west-northwest
trending chain of volcanoes parallel to the mid-American trench (Figure
1). The Atitlán caldera has erupted at least five times in the last
85,000 years. The largest caldera event (300 km3), 85,000 years ago,
formed tephra that has been located and identified from Florida's coast
to Ecuador [Drexler, et al., 1980] and formed a voluminous ignimbrite whose
deposits occur throughout much of the Guatemalan Highlands and Pacific
coastal plain. Since this major caldera-forming event, three stratovolcanoes
have formed within and near the caldera. Atitlán borders the
southern rim of the Atitlán caldera, while the other two stratovolcanoes,
Tolimán and San Pedro, are situated within the caldera. Geochemical
data suggests separate but contemporaneous magma bodies that travel through
the crust at different rates; Atitlán magma is processed more effectively
and at greater frequencies [Halsor, 1988]. The activity at Tolimán
and San Pedro produces thick lava flows or lava domes and some tephra (ash
and scoria) layers whereas Atitlán erupts more explosively to form
pyroclastic flows and widespread tehpras. Atitlan lava flows tend to be
thin and blocky.
The behavior of Atitlán Volcano is similar to that of Fuego Volcano
to the east, which has erupted several times in the past four decades.
Investigation of the analogy is important because Fuego's eruptions are
familiar by direct observations. Field exposures show that Atitlán
volcano has produced tephra, pyroclastic flows, lahars and some lava flows.
Around Atitlán volcano clastic material in the form of tephras and
pyroclastic flows is very prevalent. In the past ten thousand years
at least thirty tephras from Atitlán have blanketed the area.
Commonly, pyroclastic and lava flows have accompanied these eruptions.
Pyroclastic flows, by analogy with Fuego, probably result both from fragmentation
of lava flows descending steep slopes, and from explosive vertical eruptions
that reach to the stratospheric levels for periods of hours. Lahars
occur syn- and post-eruption from remoblized clastic material. Lahars
carry highest risk to great distances from the cone.
Atitlán's explosive nature, frequency of eruptions, and the prevalence
of agricultural development indicates the need for a volcano hazard evaluation.
Moreover, the thick jungles on Atitlán volcano are home to the national
bird, the quetzal, and one of the only remaining localities these native
animals still inhabit. Around the volcano, people live on plantations
(fincas) and in villages. These communities harvest coffee, rubber,
sugar cane, macadamia, tea, bananas and lumber, which are all-important
cash crops for Guatemala. Economic pressure has pushed the agricultural
activities higher up the slope of Atitlán, and closer to the source
of possible future volcanic activity.
Hazard
Poster from Cities on Volcanoes Meeting: Hawaii 2003
2003-Present:
Graduate Research, Michigan Technological University, Houghton, MI
Conducted field reconnaissance on the youngest large caldera-forming event
from Atitlán Caldera, "Los Chocoyos". Los Chocoyos produced
a voluminous ignimbrite whose deposits occur throughout much of the Guatemalan
Highlands and Pacific coastal plain and a widespread tephra whose deposits
occur from Florida's coast to Ecuador.
Proposal of Dissertation Research:
Physical Volcanology of Los Chocoyos, 84ka eruption
of Lago de Atitlán, Guatemala
Project Summary
The largest and most intensive eruptions on Earth frequently
show abrupt transitions between high, sustained convecting plumes and collapsing
columns, which produce regional devastation. These sudden changes may indicate
caldera collapse or decreases in mass discharge rates, both of which can
produce distinctive patterns in fallout distribution and composition. Although
these large events are rare, they have occurred repeatedly through history
and it is important to understand such events better before the next one
occurs. Studies of the physical volcanology of such eruptions are
rare, but provide essential data for modeling studies of eruption mechanisms
and for understanding the potential effects of these devastating events.
This proposal aims to identify and constrain the
eruption and fallout mechanisms for large explosive eruptions, through
intensive field and laboratory study of pyroclastic deposits of the 84-ka
eruption of Atitlán caldera in western Guatemala.
The Los Chocoyos Ash erupted from the Atitlán
caldera in Guatemala 84,000 years ago. This is one of the best-exposed
deposits of a large eruption in the world, and as such is an ideal example
from which to learn about the evolution of very large eruptions, and the
potential hazards such eruptions generate. Preliminary mapping of
the Los Chocoyos deposit and its transitional zones reveals numerous, well
exposed sites throughout the Guatamalan Highlands; there is also an extensive
deep-sea record of deposits.
The field mapping proposed here, combined with the
lab analyses, will establish compositional gradients of the deposit in
both time and space, which allows reconstruction of the eruption conditions.
The key aspects of the analyses are grain size, density, vesicularity,
petrology, chemistry, and age dating. Through detailed sampling and
careful analysis, vent and conduit geometry can be constrained; the timing
and extent of caldera collapse can be documented; magma volatile content,
ascent velocity, crystallization history, and temperature can be inferred;
and evaluation of the types and transitions of fall- and flow-deposit processes
can be determined.
The intellectual merits include:
-Extensive sampling, characterization and interpretation of perhaps
the best preserved pyroclastic fallout and surge deposits from a high-intensity,
high-volume eruption.
-Increased understanding of and physical constraints on the processes
involved in very large plinian eruptions. For example, the mechanisms that
drive major shifts from stable to collapsing plumes- and from steady, high
mass fluxes to unsteady, low mass fluxes, and the consequences for regional
deposition as a result of these shifts.
Outreach and broader impacts include:
-A better understanding of the potential regional hazards posed by
very large eruptions, which, although rare, will lead to a better assessment
of their potential impacts.
-Development of a framework for student-focused, multi-institutional
studies of volcanology. This project features strong collaboration
among the unique personnel and resources from MTU, University of Hawaii,
the U.S.G.S., and the Guatemalan hazard and geoscience agencies.
MY
RESEARCH
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