Arenal Volcano

Arenal erupted continuously for 42 years (1968–2010), making it one of the longest-duration eruptions in the Western Hemisphere during that period.

The 1968 eruption killed 87 people and destroyed three villages — Tabacón, Pueblo Nuevo, and San Luis — within minutes of the initial blasts.

Before the 1968 eruption, Arenal was not recognized as a significant volcanic threat and was referred to locally as 'Cerro Arenal' (Arenal Hill) or 'Pan de Azúcar' (Sugarloaf).

Arenal is the youngest stratovolcano in Costa Rica, with its first known eruptions dating to only approximately 7,000 years ago.

The volcano has produced at least ten VEI 4 explosive eruptions over 7,000 years, occurring at remarkably regular intervals of roughly 300–500 years.

Lake Arenal, immediately west of the volcano, is Costa Rica's largest lake and generates approximately 12% of the country's electricity through the Arenal hydroelectric dam.

During the 1968–2010 eruption, Arenal's nighttime Strombolian displays — incandescent lava fountains visible from La Fortuna — transformed the region into Costa Rica's top tourism destination.

The town of La Fortuna, just 6 km from the summit, grew from a small agricultural village to a bustling tourist hub of approximately 20,000 residents during Arenal's active decades.

Cerro Chato, Arenal's extinct predecessor volcano located 3 km to the southeast, last erupted approximately 3,500 years ago and now contains a lake-filled summit crater.

The cumulative lava output during the 42-year eruption was approximately 0.6 km³ — enough to substantially rebuild the volcano's western flank.

Arenal sits within a volcanic chain that has migrated northwestward over time: from the extinct Los Perdidos domes, through Cerro Chato, to the modern Arenal cone.

The Tabacón Hot Springs on the volcano's northern flank are heated by residual volcanic activity and maintain temperatures up to 65°C (149°F).