Pululahua

Geography & Climate

Pululahua is located in Ecuador, within the Northern Andean Volcanic Arc of the broader South America Volcanic Regions. Situated at 0.05° N, 78.49° W in the Northern Hemisphere, the volcano lies within a tropical climate zone. At 3,360 meters above sea level, Pululahua rises above the surrounding terrain into montane or subalpine conditions. The elevation creates distinct ecological zones along its flanks, from forested lower slopes to exposed rocky terrain near the summit. The volcanic landform is characterized as a caldera, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Pululahua 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 Ecuador near Pululahua, 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 dacite, an intermediate to silica-rich volcanic rock. This composition typically produces more viscous magma, leading to more explosive eruptions with ash columns and pyroclastic flows. Andesitic and dacitic magmas build pressure before erupting, which is why volcanoes with this rock chemistry are often associated with Plinian-style eruptions that can send ash tens of kilometers into the atmosphere and disrupt aviation across entire regions.

Eruption History Summary

Pululahua has 4 recorded eruptions in the geological database, spanning from 4800 BCE to 290 CE. The most powerful recorded event was a paroxysmal eruption with devastating regional consequences in 690 BCE, reaching VEI 5 on the Volcanic Explosivity Index. Notable eruptions include 450 BCE (VEI 4), 690 BCE (VEI 5). These eruptions span roughly 5,090 years of volcanic history.

Significance

With a maximum recorded VEI of 5, Pululahua has demonstrated the capacity for paroxysmal eruptions comparable to the 1980 eruption of Mount St. Helens. Eruptions of this scale can devastate areas within 20-30 kilometers and produce ash fall that disrupts aviation and agriculture across hundreds of kilometers.

GVP Reference Summary

Pululahua is a relatively low, forested volcano about 15 km N of Quito. The 5-km-wide summit caldera is narrowly breached to the west and partially filled by a group of dacitic lava domes. Pre-caldera lava domes of different ages are found outside the caldera to the E, SE, and S. Four post-caldera domes rise up to 450 m above the caldera floor. Large explosive eruptions producing pyroclastic flows took place during the late Pleistocene and Holocene. Caldera formation took place during a series of eruptions lasting 150-200 years beginning about 2,650 radiocarbon years ago. The latest dated eruption occurred from the post-caldera lava domes about 1,670 years ago and produced lava flows and pyroclastic flows.

— Smithsonian Institution, Global Volcanism Program