Costa Rica Field Module - GSC 491L/499
Costa Rica Pacific Margin: Geomorphology and Tectonics
Dr.
Jeff Marshall & Dr. Jon Nourse
Geological Sciences Department
Required Assignments – Spring 2008
3. Volcán Poás Exercise
During our trip to Volcán Poás, we will visit
the active summit crater and walk along a trail to the paleo-crater of Laguna
Botos. In your field notebook, you should make detailed sketches of the main
crater and its deposits as viewed from the observation platform. We will
provide a topographic map and a geologic map of the summit area to aid in your
interpretation. Compare your observations and sketches to the maps. For this
assignment, you will construct a topographic profile and geologic cross section
across the crater using the topo map, geologic map, and your sketch. You will
submit your first drafts of these illustrations (field version) for grading
while we are in Costa Rica. Final drafts (office version) will be submitted
with your complete field module report due in early Spring Quarter.
a.
Draft Topographic Profile and Cross Section — (10 pts)
(Due in Costa Rica - March 30, 8 am)
Each student shall submit professionally drawn “first
drafts” of: 1) a geologic cross section of the Volcán Poás main crater (along
line A-A’ on the geologic map); and 2) a topographic profile across the summit
of Volcán Poás (along line B-B’ indicated by the instructors). Be sure to
include all pertinent data related to geologic units, vertical and horizontal
scale, section azimuth, map location, etc.
b.
Final Volcán Poás Illustrations and Report — (10 pts)
(Due as part of Final Field Module Report – Monday,
April 21, 5 pm)
a. Produce a final geologic cross-section
(with no vertical exaggeration) along line A-A' indicated on the geologic map
of the Poás main crater. Pay close attention to the age relationships between
the units, and the mode of deposition. Also note the outcrop pattern all the
way around the crater. For example, recognize that the crater-lake deposits fill
the crater depression, and that later tephra/ash deposits will drape across
prior topography. Be sure to include all standard information on your cross
section regarding scale, azimuth, unit symbols, etc.
b. Produce a final topographic profile
along line B-B' across the Volcán Poás summit. In addition to standard information, label all
significant features including the active and paleo craters.
c. Write a succinct
one-page report on your field observations at Volcán Poás and your
interpretations from the cross section and topographic profile.