Santa Rosa National Park, Santa Elena Peninsula, Costa Rica
After a night of travel, we arrived to a beautiful sunny morning in Isla Murcielago (“Bat Island,” although no bats were in evidence) in Santa Rosa National Park on the Santa Elena Peninsula. This whole peninsula is a section of ocean floor material that has been disconnected from a subducting plate and attached to the overriding Caribbean Plate. As such, it contains a good deal of peridotite (rock rich in olivine, or “peridot”), and in some places also contains the top section of ocean floor material, pillow basalts, which we were lucky enough to see right on the beach this morning. These basalts occur in rounded shapes, and have a black glassy (obsidian) rind with a coarser interior, which weathers reddish due to the iron contained in the rock. In addition, just a few feet away was a natural concrete material, made of basalt, sand, and shells all cemented together by calcite into what geologists would call a limestone conglomerate. While some were examining the geology, a set of intrepid souls braved a strenuous hike up to the top of the ridge of Isla Murcielago, where they were rewarded with spectacular views of the surrounding area. When they rejoined the beach group, many partook of the excellent swimming and snorkeling, spotting (among many others) trumpet fish up to about six feet long in the great (more than 30 feet) visibility.
In the afternoon, we made our way southeast around the peninsula to Bahia Huevos (“Bay of Eggs,” but no eggs here, either). While some of us went snorkeling again (not as good as the morning, but still enjoyable), a number of us toured a waterway through a mangrove forest, in both zodiacs and kayaks. Although the trip began with a sprinkling of rain, it progressed to a refreshing shower, and by the time the last of us in the kayaks came to the pickup spot, was a downpour. However, our wet journey afforded us some amazing sights and sounds, including trees full of nesting pelicans and the call of the howler monkey near the beginning of the shower.
