Volcanoes in Costa Rica

Costa Rica has 10 Holocene volcanoes arrayed along the Central American Volcanic Arc, a chain of more than 100 volcanic centers that stretches from Guatemala to Panama above the Cocos–Caribbean subduction zone. Despite occupying just 51,100 km² — roughly the size of Slovakia — the country contains some of Central America's most frequently active and most closely monitored volcanoes. [[volcano:poas|Poás]], which erupted most recently in 2025, has recorded over 60 eruptions since approximately 7920 BCE, making it one of the most prolific eruptors in the Western Hemisphere. [[volcano:arenal|Arenal]], a near-perfect conical [[special:types-of-volcanoes|stratovolcano]], maintained almost continuous activity from 1968 to 2010 and became one of the world's best-studied volcanoes during that period. Costa Rica's volcanic backbone runs northwest to southeast through the Cordillera Central and the Cordillera de Guanacaste, with summits reaching from about 1,659 m at Orosí to 3,436 m (11,273 ft) at [[volcano:irazu|Irazú]], the country's tallest volcano.

The proximity of these volcanoes to the densely populated Central Valley — home to San José and roughly 60% of Costa Rica's 5.2 million people — makes volcanic hazard management a national priority. Costa Rica's National Seismological Network (RSN) and the Volcanological and Seismological Observatory of Costa Rica (OVSICORI) jointly monitor all active centers. The country also harnesses its volcanic geology for geothermal energy, with the Miravalles Geothermal Plant alone generating approximately 163 MW, about 15% of Costa Rica's electricity.

Volcanism has shaped Costa Rica's identity as a global ecotourism destination, with volcanic national parks drawing more than 1.5 million visitors annually.

Costa Rica's volcanism is driven entirely by the subduction of the Cocos Plate beneath the Caribbean Plate along the Middle America Trench, approximately 100 km off the Pacific coast. The Cocos Plate converges at roughly 72–85 mm per year — one of the faster subduction rates on Earth — with the slab descending at angles between 30° and 60° beneath the continental crust. As the plate descends to depths of approximately 100–150 km, hydrated minerals in the slab release water into the overlying mantle wedge, lowering its melting point and generating andesite-to-basaltic-andesite magmas that ascend to feed the volcanic arc.

The volcanic front in Costa Rica is divided into two distinct segments: the Cordillera de Guanacaste in the northwest, which hosts Orosí, Rincón de la Vieja, Miravalles, and Tenorio; and the Cordillera Central in the heart of the country, containing Platanar, Poás, Barva, Irazú, and Turrialba. Arenal sits at the transition between these two segments. A notable feature is the 'Arenal gap' — a zone of reduced volcanic activity that separates the two cordilleras, possibly linked to a change in the angle of the subducting slab.

Unlike the [[special:ring-of-fire|Ring of Fire]]'s Pacific island arcs, Costa Rica's volcanic arc sits on thickened continental crust exceeding 25 km, which influences magma composition and eruption style. The dominant rock types across all Costa Rican volcanoes are andesite and basaltic andesite, consistent with typical subduction-zone magmatism. Compared to its neighbor [[country:nicaragua|Nicaragua]], whose thinner crust produces more basaltic volcanism, Costa Rica tends toward more explosive eruption styles.

**Irazú** — At 3,436 m (11,273 ft), [[volcano:irazu|Irazú]] is Costa Rica's tallest volcano and one of the most massive, covering approximately 500 km². Its broad summit hosts multiple craters, including the well-known green-hued Diego de la Haya crater lake. Irazú's most significant recent eruption occurred from 1963 to 1965, coinciding memorably with U.S. President John F.

Kennedy's state visit to Costa Rica in March 1963. That eruption deposited ashfall across the Central Valley, damaging agriculture and causing lahars that destroyed portions of Cartago. With 24 confirmed eruptions and a VEI maximum of 3, Irazú remains a closely watched threat to the 2.5 million people living within 35 km of its summit.

**Poás** — [[volcano:poas|Poás]] (2,697 m / 8,848 ft) is one of the most active volcanoes in Costa Rica, with 63 confirmed eruptions spanning nearly 10,000 years. Its summit features Laguna Caliente, one of the world's most acidic natural lakes (pH near zero), which occupies the northern active crater. Poás erupts primarily through phreatic and phreatomagmatic explosions — geyser-like ejections of superheated crater-lake water that can reach hundreds of meters high.

A significant eruption in April 2017 forced the closure of Poás Volcano National Park for over a year and destroyed the crater lake temporarily. The volcano has continued episodic activity through 2025.

**Arenal** — [[volcano:arenal|Arenal]] (1,670 m / 5,479 ft) is Costa Rica's youngest and most iconic stratovolcano. A catastrophic eruption on July 29, 1968 — after approximately 500 years of dormancy — killed 87 people and destroyed the villages of Tabacón, Pueblo Nuevo, and San Luis with pyroclastic flows and ballistic projectiles. From 1968 to 2010, Arenal maintained near-continuous Strombolian and Vulcanian activity, producing lava flows, ash plumes, and incandescent rockfalls visible from the popular tourist town of La Fortuna.

With 27 confirmed eruptions and a VEI max of 4, Arenal is one of the most thoroughly studied volcanoes in Latin America.

**Turrialba** — [[volcano:turrialba|Turrialba]] (3,340 m / 10,958 ft) is the easternmost of Costa Rica's Holocene volcanoes and sits across a broad saddle northeast of Irazú. After 130 years of quiet following eruptions in 1853–1866, Turrialba reawakened in 2010 with increased fumarolic activity. By 2014–2015, full phreatomagmatic eruptions returned, producing ash columns up to 4 km high that reached San José's Juan Santamaría International Airport and forced temporary flight cancellations.

Turrialba has 21 confirmed eruptions and a VEI max of 4, recorded around 40 CE.

**Rincón de la Vieja** — Known as the 'Colossus of Guanacaste,' [[volcano:rincon-de-la-vieja|Rincón de la Vieja]] (1,729 m / 5,673 ft) is a complex volcanic massif with 12 craters and cones spread along a 20-km arcuate ridge within the 15-km-wide Guachipelín caldera. It is the most active volcano in northwestern Costa Rica, with 30 confirmed eruptions since approximately 1820 BCE. The volcano produces frequent phreatic explosions from its acidic summit crater lake, and its eruptions pose lahar hazards to surrounding communities.

Activity in 2024 included multiple phreatic blasts.

**Miravalles** — [[volcano:miravalles|Miravalles]] (2,028 m / 6,654 ft) is a large stratovolcano in the Cordillera de Guanacaste that hosts Costa Rica's most important geothermal energy complex. With only two confirmed eruptions (most recently in 1946, VEI 1), it is among the quieter volcanoes, but its extensive hydrothermal system — including hot springs, fumaroles, and mud pots — indicates an active magmatic system at depth.

**Tenorio** — Volcán Tenorio (1,916 m / 6,286 ft) lacks confirmed historical eruptions but is notable for the Río Celeste, a strikingly turquoise river produced by the mixing of volcanic mineral-laden waters. Tenorio Volcano National Park is a major ecotourism destination in the Cordillera de Guanacaste.

Costa Rica's volcanoes have a combined record of approximately 185 eruptions spanning the last 10,000 years, with at least 159 confirmed events documented across six active volcanic centers. The eruption record is dominated by Poás (63 confirmed), Rincón de la Vieja (30), Arenal (27), Irazú (24), and Turrialba (21). Eruption frequency has accelerated in the modern instrumental period: between 2010 and 2025, five of Costa Rica's six historically active volcanoes produced eruptions, sometimes simultaneously.

The most destructive eruption in Costa Rica's modern history was Arenal's 1968 event, which killed 87 people — the only eruption to cause fatalities in the country during the 20th century. The Irazú eruption of 1963–1965 caused the greatest economic damage, with ashfall destroying coffee crops across the Central Valley and lahars devastating infrastructure in the Reventazón and Sarapiquí river valleys. Looking further back, the prehistoric record reveals powerful events: Arenal produced at least 15 eruptions of VEI 4 magnitude between 5060 BCE and 1525 CE, and Turrialba and Barva each produced VEI 4 events thousands of years ago.

The most powerful eruption in Costa Rica's Holocene record belongs to Rincón de la Vieja, which generated a VEI 4 event around 1820 BCE. In the 21st century, the pattern has shifted toward frequent, moderate phreatic eruptions at Poás, Turrialba, and Rincón de la Vieja — a reflection of both increased monitoring sensitivity and genuinely heightened activity across the arc.

Costa Rica faces a distinctive combination of volcanic hazards amplified by high population density, steep terrain, and abundant rainfall. The primary hazard types include ashfall, lahars (volcanic mudflows), pyroclastic flows, lava flows, volcanic gases, and ballistic projectiles. Ashfall is the most widespread hazard: the Irazú 1963–1965 eruption deposited centimeters of ash across the Central Valley, clogging waterways, collapsing roofs, and disrupting San José's water supply.

Lahars — triggered when eruptions interact with crater lakes or heavy tropical rainfall on loose volcanic deposits — pose the greatest threat to populated valleys. Rincón de la Vieja's phreatic eruptions frequently trigger small lahars down its northern drainages, and Irazú's 1963 lahars killed at least 20 people. Pyroclastic flows, though less frequent, produced the deadliest event in modern Costa Rican volcanic history when Arenal's 1968 eruption sent high-speed flows 5 km from the summit.

Volcanic gas emissions — particularly sulfur dioxide and hydrogen sulfide — are a chronic hazard at Poás and Turrialba, periodically reaching populated areas downwind. The proximity of Costa Rica's volcanic centers to the Central Valley, where over 3 million people reside, and to Juan Santamaría International Airport makes ashfall and gas emissions national-level threats. OVSICORI and the RSN maintain real-time monitoring networks with seismometers, GPS stations, gas analyzers, and webcams at all active volcanoes.

Costa Rica's National Emergency Commission (CNE) coordinates evacuation planning and hazard zone mapping.

Costa Rica's 10 Holocene volcanoes are distributed along two parallel mountain ranges running from northwest to southeast, forming the backbone of the country. The Cordillera de Guanacaste in the northwest contains four volcanoes: Orosí (1,659 m) at the Nicaraguan border, Rincón de la Vieja (1,729 m), Miravalles (2,028 m), and Tenorio (1,916 m). This segment trends northwest–southeast and sits roughly 170 km from the Middle America Trench.

Further southeast, the Cordillera Central contains five volcanoes in close succession: Platanar (2,267 m), Poás (2,697 m), Barva (2,906 m), Irazú (3,436 m), and Turrialba (3,340 m). These are the tallest volcanoes in the country and sit directly above the Central Valley, the population and economic heart of Costa Rica. Arenal (1,670 m) occupies the transition zone between the two cordilleras, offset slightly to the north.

All 10 volcanoes lie within a band approximately 250 km long and 30 km wide, parallel to the Pacific coast. The volcanic front is situated roughly 150–200 km inland from the Middle America Trench, above the zone where the Cocos slab reaches depths of 100–150 km — the typical depth range for arc magma generation.

Volcanism is central to Costa Rica's national identity, economy, and global reputation. The country's volcanic soils support its world-renowned coffee industry — beans grown on the flanks of Poás, Irazú, and Barva in the Central Valley are prized for their acidity and complexity. Costa Rica leverages its volcanic landscape for geothermal energy: the Miravalles Geothermal Plant and the Las Pailas Plant (also on Rincón de la Vieja's flanks) contribute approximately 15% of national electricity generation, supporting Costa Rica's goal of carbon neutrality.

Ecotourism, the country's largest foreign-exchange earner, is heavily anchored in volcanic attractions. Arenal Volcano National Park, Poás Volcano National Park, and Irazú Volcano National Park are among the most visited destinations in the country, drawing both international and domestic tourists to crater-rim viewpoints, hot springs, hanging bridges, and cloud forest reserves. The mineral-rich Río Celeste near Tenorio and the hot springs surrounding Arenal have become iconic images of Costa Rican tourism marketing.

Culturally, the Irazú eruption of 1963 is etched into national memory — it occurred during President Kennedy's visit and symbolizes the precarious coexistence of Costa Ricans with their volcanic landscape. The national motto of 'Pura Vida' extends to an embrace of the country's geological dynamism.

Costa Rica offers some of the most accessible volcanic tourism in the world. [[volcano:poas|Poás Volcano National Park]], just 50 km from San José, allows visitors to peer into the active crater and its turquoise acid lake from a paved viewpoint — one of the easiest volcano summit experiences on Earth, though access is subject to closure during heightened activity. [[volcano:irazu|Irazú Volcano National Park]] can be reached by vehicle almost to the 3,436-m summit, where visitors look into the green Diego de la Haya crater lake on clear mornings (clouds typically roll in by midday). [[volcano:arenal|Arenal]] in La Fortuna is Costa Rica's most popular volcano tourism hub, offering hot springs resorts, hanging bridge tours, and hiking on lava flow trails — though the volcano itself has been quiet since 2010. Rincón de la Vieja National Park provides hot springs, mud pools, and waterfall hikes on the flanks of the active complex. Tenorio Volcano National Park features the ethereal Río Celeste, rated among the world's most beautiful rivers.

The best time to visit is the dry season (December–April), though volcanic conditions can change any day. Entry fees are typically $15–$18 USD for international visitors. Always check OVSICORI bulletins before visiting active volcanoes, as parks close during eruption episodes.