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Figure 1. Extent of the Markagunt gravity slide
• The role of magmatic intrusions in inflation of volcanic fields
and slope destabilization;
• Gravitational basement spreading of volcanic fields prior to
catastrophic failure;
• Comparison of structural features of the MGS with those of
low-angle normal faults;
• The use of analog and numerical modeling techniques in simu-
lating the growth of volcanic fields and sector collapse; and
• The possible importance of monitoring radial spreading of
modern volcanic fields to aid hazard assessment of potentially
catastrophic collapse, not just of individual volcanic cones, but
of entire sectors of active volcanic fields.
The subject of large-scale catastrophic failure of volcanic fields ramp fault; catastrophic versus tectonic mechanisms.
will bring together researchers and students—specialists in struc-
tural geology, rock mechanics, landslides, volcanology, petrog-
raphy, tectonics, geochronology, geophysics, sedimentology, and
modeling—using different approaches that collectively may yield
a better understanding of these rare but complex catastrophic
events. The field-based format of this forum will allow for lively
discussions, integration of ideas, and development of future
research and collaborations. Our goal is to assemble a diverse
group willing to look at the MGS from multiple angles. We see
(MGS), which moved as a single, gigantic, cata-
strophic slide, despite being larger than Rhode
Island. The ramp fault is where the slide mass
moved southward up and over the former land sur-
face at least 35 km. The Rubys Inn thrust faults
resulted from gravitational spreading of the volca-
nic field prior to MGS emplacement. The southern
margin of the newly discovered Sevier gravity slide
(SGS, which forms much of the Sevier Plateau),
possibly triggered by inflation of the 23 Ma Monroe
Peak caldera, is also shown. SLC—Salt lake City.
significant opportunities for collaborative, cross-disciplinary GSA TODAY | www.geosociety.org/gsatoday
research not only in our effort to characterize the MGS, but to
understand how it relates to other large terrestrial landslides and
volcanic provinces throughout the world.
PRELIMINARY AGENDA
The Field Forum will be based out of hotels in Cedar City and
Bryce Canyon City, Utah. Some critical outcrops will require
off-trail hiking of 1 or 2 km over locally steep slopes. Elevations
are between 1800 and 3400 m.
16 Sept.: Evening ice breaker.
17 Sept., Day 1: Half day of invited and volunteered presentations,
then a field introduction to local volcanic stratigraphy.
18 Sept., Day 2: Former land surface segment; age constraints;
mechanics of basal breccia formation.
19 Sept., Day 3: MGS breakaway area and western slide margin;
20 Sept., Day 4: Bedding-plane segment and features diagnostic of
slide margins and catastrophic emplacement.
continued on p. 24
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