Four Lava Flows

Capulin Volcano eruptions produced two types of volcanic products:

• cinders (frothy volcanic rocks)
• lava flows

The eruption began with a northwest-oriented fissure vent. From this vent, molten rock, magma, exploded thousands of feet into the air. The rock cooled as it fell back to earth. Small bits of lava rock, called cinders, and larger chunks called volcanic bombs, piled up around the vent to build the Capulin cinder cone. During this eruption, the first lava flow oozed through the cinders, flowing to the east.
After the gas in the magma was depleted, the explosive eruptions ended. Lava then oozed out of a fissure on the west side of the cinder cone. These flows moved at least partly in lava tubes, from this fissure, later called the "Boca" which is Spanish for "mouth". This second lava flow went south, the third to the southwest, and finally the fourth to the northeast and north, covering almost 16 square miles. Ripple marks or pressure ridges on the surface of the lava are perpendicular to the direction of the flow, and formed as the crust cooled but lava continued to flow underneath. Lava mounds called tumuli (squeeze-ups) formed where the lava crust broke and lava spewed out under pressure.