San Martin

Geography & Climate

San Martin is located in Mexico, within the Trans-Mexican Volcanic Arc of the broader Middle America-Caribbean Volcanic Regions. Situated at 18.57° N, 95.20° W in the Northern Hemisphere, the volcano lies within a tropical climate zone. With a summit elevation of 1,650 meters above sea level, San Martin is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

San Martin sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Mexico near San Martin, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is trachybasalt / tephrite basanite, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

San Martin has 16 recorded eruptions in the geological database, spanning from 3440 BCE to 1932 CE. The most powerful recorded event was a cataclysmic eruption with ash columns reaching the stratosphere in 1793 CE, reaching VEI 4 on the Volcanic Explosivity Index. Notable eruptions include 1793 CE (VEI 4), 1664 CE (VEI 3). This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. The most recent eruption in 1932 CE places this volcano within the modern era of volcanological observation.

Significance

With a maximum recorded VEI of 4, San Martin has demonstrated the capacity for significant explosive eruptions that can impact regional aviation, agriculture, and communities tens of kilometers from the summit. VEI 4 eruptions produce ash columns reaching 15-25 kilometers into the atmosphere. With 16 recorded eruptions, San Martin has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the Middle America-Caribbean Volcanic Regions region.

GVP Reference Summary

Volcán de San Martín, part of the Tuxtla volcanic field, is a broad alkaline shield volcano that rises above the Gulf of Mexico. The massive volcano, also known as San Martín Tuxtla, is elongated NW-SE and is capped by a 1-km-wide summit crater. The upper part of the volcano is covered with dense tropical rain forests. The summit and flanks contain more than 250 pyroclastic cones and maars. Well-preserved cinder cones are abundant between the summit and Laguna Catemaco on the SE flank. Holocene cones in this area produced ash deposits that buried stone pyramids. The two largest recorded eruptions took place in 1664 and 1793. The 1793 eruption occurred from two cinder cones in the summit crater and produced widespread ashfall and lava flows that extended 3.5 km down the NE flank.

— Smithsonian Institution, Global Volcanism Program