La Pasarela is the result of multiple, voluminous lava flows that flooded the Rio Grande, forming a natural dam that impounded the waters of this river. Over time, the river waters made their way through this basalt, forming what we see today at the site.

The Rio Grande Valley was filled with lava from the eruptions, reaching a thickness of about 100 m. The multiple lava units near the Rio Grande Valley also provide an interesting opportunity to study the complexity of these lava fields.