The Arenal Volcano is an andesitic stratovolcano located in north-central Costa Rica, approximately 90 kilometers northwest of the capital, San José. This conical mountain rises to 1,670 meters above sea level and is known for its strikingly symmetrical shape, making it an iconic national landmark. Geologically, it is considered a young volcano, with an estimated age of less than 7,500 years. Its prominent presence has shaped the surrounding landscape, ecology, and economy of the region.
Geological Significance and Scientific Study
The volcano’s geological history is defined by its dramatic reawakening on July 29, 1968, after centuries of dormancy, which fundamentally altered the area and placed Arenal on the global scientific map. This sudden vulcanian-style eruption lasted for several days, devastating over 15 square kilometers of land and destroying the villages of Tabacón and Pueblo Nuevo. The initial blast claimed 87 lives, primarily due to pyroclastic flows and ejected ballistic rocks.
This event marked the beginning of a period of almost continuous activity that lasted until 2010, characterized by Strombolian explosions, lava flows, and gas emissions. For over four decades, Arenal provided volcanologists with a unique “natural laboratory” to study the behavior of stratovolcanoes within the Central American Volcanic Arc. Scientists closely monitored its magma dynamics, gas emissions, and seismic activity.
The 1968 eruption and the subsequent effusive phase allowed researchers to analyze the evolution of the magma, which changed from andesite to basaltic andesite over time. This continuous activity offered invaluable data for risk assessment and developing better predictive models for future volcanic events worldwide. While the volcano has been dormant since 2010, the geological legacy of its 42-year eruption cycle remains a subject of intense scientific interest.
Economic Engine: Tourism and Local Development
The dramatic geological activity of the Arenal Volcano transformed the region from a quiet agricultural community into one of Costa Rica’s primary economic drivers. The constant, visible eruptions between 1968 and 2010 attracted hundreds of thousands of international visitors, creating a robust tourism industry centered on the spectacle. This influx of travelers led to the rapid development of infrastructure, particularly in the nearby town of La Fortuna.
La Fortuna has become the third most visited area in the country, attracting an estimated 1.5 million visitors annually. The area features numerous tourism developments, including over 38 thermal spring resorts that utilize the volcano’s geothermal heat for relaxation. The region also offers adventure sports and nature tours, which generate significant revenue and support thousands of local jobs.
More than 90 percent of the companies in the area are locally or nationally owned, meaning tourism revenue directly supports the regional economy and provides diverse employment opportunities. The success of the tourism sector has fostered a strong focus on ecotourism. This model recognizes the interdependence of environmental conservation and economic prosperity, creating a sustainable source of income for local residents.
The Role of Lake Arenal in National Hydropower
Lake Arenal is a man-made reservoir near the volcano that is a major component of Costa Rica’s energy infrastructure and commitment to renewable power. In the 1970s, the original natural lake was tripled in size to 85 square kilometers by the construction of the Presa Sangregado Dam to maximize hydroelectric power generation.
The reservoir’s water is channeled through the Arenal Hydroelectric Plant, a foundational element of the national energy grid. This single facility generates approximately 12 percent of the country’s total electrical power. This project allows Costa Rica to harness its high volume of annual rainfall, making hydroelectricity the largest source of clean energy.
The reliable energy output from Lake Arenal helps the country maintain an electrical grid powered almost entirely by renewable sources. Beyond electricity, the reservoir also supplies water for irrigating thousands of hectares of agricultural land, supporting regional economic stability and food production.
Ecological Diversity of the National Park
The Arenal Volcano National Park, established in 1991, covers a vast area that includes the volcano and its surrounding landscapes, protecting a remarkable concentration of biodiversity. The volcano’s presence creates distinct microclimates and sharp elevation gradients, facilitating the transition between dense rainforest and cloud forest ecosystems.
The park acts as a sanctuary for an impressive variety of species, contributing significantly to the region’s biological richness. Over 500 bird species have been identified within the park boundaries, accounting for approximately 53% of all bird species found in Costa Rica. This makes the area a globally significant destination for ornithology.
The fertile volcanic soil, enriched with minerals from past eruptions, supports a lush flora, including numerous species of orchids, heliconias, and bromeliads. The protected area is also home to diverse fauna, including three species of monkeys, tapirs, and ocelots. This unique environment underscores the volcano’s role in fostering and conserving ecological heritage.