The Rincon de la Vieja Volcano, a massive active andesitic volcano, located 25 kilometers (15 miles) northeast of Liberia in northwestern Costa Rica. This complex includes at least nine different craters with its two well-known cones: the quiet, 6,286-foot Santa María (the highest point in the park) and the steaming Von Seebach crater within a three-mile-wide caldera with 1,640-foot-wide acid lake that is exposed on the southern side with most of its activity centered on its younger southeastern flanks. The active crater contains a steaming lake that has, from time to time, erupted, throwing volcanic ash and boiling mud flying into the air and down the numerous rivers in the park.
According to the Smithsonian’s Global Volcanism Program, its last major eruption occurred approximately 3,500 years ago but it has since remained highly active with some periods of smaller eruptions. Its most important one occurred from 1995 to 1998, predominantly between February and September 1998 that caused mountain-side residents to flee in those years.
In September 2011, Rincon de la Vieja experienced a couple mini eruptions sending large plumes of smoke in the air. (Hiking to the summit has not been permitted since).
In September 29th, 2017 the volcano had another significant eruption with a column that reached more than 1,000 meters over the crater. The column of gas and materials was easily visible from different areas in Guanacaste, and due to the lack of wind in the area there was mild dispersion of the same to the west. According to the Costa Rica National Emergency Committee, the area to the north of the volcano, was affected by lahars, (mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water).
In October 3rd, 2017 the Rincon de la Vieja Volcano registered an eruption that reached over 1,500 meters above the top of the crater, 3,416 meters above sea level (11,204.48 ft), this eruption, is considered by the National Seismology Network the biggest phreatic eruption this volcano had since 2011.
Although it has remained relatively quiet since then, it has maintained high activity, with a lot of fluid movement and high hydrothermal activity in main crater. Underneath, rivers of lava continue to boil beneath its external layers, which fuel the series of volcanic components with fumaroles, hot springs, mud pots, and geysers. It is often stated that the park is a smaller version of the Yellowstone National Park in the United States.