Irazu: A Deep Dive into Costa Rica's Highest Volcano
Irazu is the highest volcano in Costa Rica, a massive presence looming over the Central Valley where most of the country's population lives. From its summit on a clear day, visitors can reportedly glimpse both the Pacific and the Caribbean, an extraordinary panorama from a single peak. But Irazu is best remembered for a prolonged eruption in the 1960s that buried the capital, San Jose, under repeated falls of ash and reshaped the region's relationship with its towering neighbour.
The roof of Costa Rica
Irazu reaches about 3,432 metres, making it the highest volcano in the country. It is a broad, complex stratovolcano with several craters at its summit, including a striking main crater that has at times held a coloured lake. Its great height and proximity to the densely populated Central Valley give it a commanding presence over the heart of Costa Rica.
A view of two oceans
One of Irazu's most celebrated features is the claim that, on exceptionally clear days, both the Pacific Ocean and the Caribbean Sea can be seen from its summit. Such days are rare, as the high peak is often shrouded in cloud, but the possibility has long drawn visitors to the summit, reachable by road within Irazu Volcano National Park.
The 1963-1965 eruption
Irazu's defining modern event was a long eruption that began in 1963, coinciding with a visit by the President of the United States, and continued for about two years. The volcano repeatedly showered ash across the Central Valley, including the capital San Jose, disrupting daily life, damaging agriculture, and clogging waterways. The prolonged ashfall and subsequent lahars caused significant hardship across the region.
Living beneath the ash
The 1963-1965 eruption left a lasting mark on Costa Rica. For two years, residents of the Central Valley contended with ash that coated streets, roofs, and crops, and the heavy deposits later combined with rain to produce destructive mudflows. The experience shaped the country's awareness of volcanic hazards and contributed to the development of its volcano monitoring and disaster response capabilities.
The summit craters
Irazu's summit is a stark, barren landscape of grey volcanic terrain, in striking contrast to the green farmland on its lower slopes. The main crater is a deep, steep-walled pit that has at times held a small lake whose colour varies with the volcano's chemistry. Walking among the craters offers visitors a vivid sense of the volcano's raw, active character.
Fertile slopes and agriculture
Despite the hazards, Irazu's slopes are intensively farmed, their volcanic soils supporting dairy farming and vegetable cultivation that help feed the Central Valley. This is the familiar paradox of volcanic regions: the same volcano that threatens with ash and lahars also enriches the land, drawing people to live and work close to its base.
Monitoring the giant
Costa Rica's volcanological and seismological institute monitors Irazu as part of the national network watching the country's active volcanoes. Although Irazu has been relatively quiet since the 1960s, it is not extinct, and continuous monitoring of its seismicity and gas emissions remains essential given its height and its proximity to so much of the country's population.
Explore on the map
Irazu stands among Costa Rica's chain of volcanoes, alongside Arenal, Poas, and Turrialba. Explore it on the interactive map — filter by country to see Irazu among Costa Rica's volcanoes and to place this towering peak within the volcanic arc of Central America.