With our trip coming to its last days (!!!!), our class took to the field for the penultimate time. Previously we had characterized the lithologies of pyroclastic flows and ash deposits from our time with Costa Rican Geologist Guillermo Alvarado. Combined, these rock units span a period of 5 million years across as many as 10 different members from the Liberia and Bagaces formations. Our previous day of mapping gave the now potentially false assumption that our units were nearly laid out in their original stratigraphic order. However on a new road with new outcrops, our confidence about the nature of our mapped units quickly turned into confusion, as what we observed slowly began to contradict our previous assumptions. After many observations, a creek crossing, and one casual warning about road safety later, we’re still confused—but excitement remains high as we slowly uncover the geologic treasures of an unmapped area!

Looking forward, we are left with a final day on the beach looking at volcaniclastic conglomerates, but then the possibly daunting task of putting our field maps into greater geologic context. Are all units stratigraphically unaltered? If not, to what degree has our field area been under the influence of tectonics or local changes in stratigraphic order? Are some units simply not as far reaching as others? Will Andrew ever brush his teeth before leaving for the field?

We’re not done mapping.

             – final haiku by Matt Barr (17.5)