The tectonic setting of our research area is at the northernmost edge of the plate boundary between the South American continent and the oceanic plate to the west of South America, known as the Nazca Plate. The Nazca Plate is sinking below the South American continent through a process known as subduction. The shape of the downgoing Nazca plate below South American is somewhat wavy - in some places, the slab dips more steeply, in others, it sinks to about 100 km depth and then flattens out, forming what we call "flat slab" regions. Learn more about this plate boundary and flat slab subduction in the video below:
Colombia is at the far northern edge of this plate boundary. It also lies along the boundary with the Caribbean plate. Prior to 15 million years ago, North and South America were separated by the Central American Seaway - part of the Caribbean Sea that extended between what are now Panama and Colombia. Approximately 15 million years ago, Panama - along with a strip of land that is now the northwestern coast of Colombia (the Choco Block) - first made contact with northwestern South America, effectively closing the Central American Seaway. Over the course of a few million years, the Choco block became attached along the western margin of Colombia, as the Caribbean Sea was pinched out from South to North. After that, the Caribbean plate continued to subduct along the northernmost edge of Colombia, while the Nazca plate subducts along the western margin.