OVSICORI-UNA reported that occasionally during early mornings in July web-camera images showed a plume rising from Arenal that drifted SE and S. Scientists that conducted fieldwork during 29-30 July observed plumes rising from the last cone that formed in the NE part of Crater C.

3 August 2011            Back to Top

OVSICORI-UNA reported that occasionally during early mornings in July web-camera images showed a plume rising from Arenal that drifted SE and S. Scientists that conducted fieldwork during 29-30 July observed plumes rising from the last cone that formed in the NE part of Crater C.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

15 December 2010            Back to Top

OVSICORI-UNA reported that during November, activity originating from Arenal's Crater C was at a low level and consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. Residents to the N, W, and S observed a decrease in gas emissions and nighttime incandescence from the crater. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

6 October 2010            Back to Top

OVSICORI-UNA reported that during September, activity originating from Arenal's Crater C was at a low level and consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. Residents to the N observed material ejected from Strombolian explosions descending the N flank. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

8 September 2010            Back to Top

OVSICORI-UNA reported that during August activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. Some of the Strombolian eruptions caused glass to vibrate in buildings located 6.5 km NE. Block avalanches descended the N and NE flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

30 June 2010            Back to Top

OVSICORI-UNA reported that during June activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. Some of the Strombolian eruptions caused glass to vibrate in buildings located 4 km N. A lava flow that began in mid-January remained active on the S flank. Avalanches from edges of the lava flow and from the N and NE crater rim descended multiple flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Small explosions of gas and occasionally ash originated from a vent N of Crater C, while Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

26 May 2010            Back to Top

OVSICORI-UNA reported that on 24 May a series of incandescent flows descended the W flank, towards the lake, reaching the forest. An ash plume drifted N. Arenal National Park was closed briefly due to the activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

19 May 2010            Back to Top

According to news articles, an eruption from Arenal on 24 May produced gas and ash emissions as well as multiple lava flows, prompting the evacuation of Arenal National Park.

Sources: Agence France-Presse (AFP)

12 May 2010            Back to Top

OVSICORI-UNA reported that during April activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, infrequent ash emissions, and occasional avalanches. A lava flow that began in mid-January remained active on the S flank. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Avalanches from the crater and from lava-flow fronts traveled down the SW, S, and SE flanks, occasionally igniting vegetation. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

7 April 2010            Back to Top

OVSICORI-UNA reported that during March activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. A lava flow that began in mid-January remained active on the S flank. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Avalanches from the crater and from lava-flow fronts traveled down the SW, S, and SE flanks, occasionally igniting vegetation. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

3 March 2010            Back to Top

OVSICORI-UNA reported that during February activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. A lava flow traveled down the SW flank. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Avalanches from the crater and from lava-flow fronts traveled down the SW, S, and SE flanks, occasionally igniting vegetation. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

13 January 2010            Back to Top

OVSICORI-UNA reported that during December activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches that traveled down the W and SW flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Avalanches from lava-flow fronts traveled down the SW flanks. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

11 November 2009            Back to Top

OVSICORI-UNA reported that during October activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches that traveled down the W and SW flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Avalanches from lava-flow fronts traveled down the SW flanks. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

7 October 2009            Back to Top

OVSICORI-UNA reported that during September activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches that traveled down the W flank. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Avalanches from lava-flow fronts traveled down the SW flanks. Crater D produced only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

24 June 2009            Back to Top

OVSICORI-UNA reported that during May activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches that traveled down the SW, S, and N flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Small avalanches traveled down several ravines. Crater D produced only fumarolic activity.

A small eruption on 16 June was verified by field observations on 17 June. The eruption caused avalanches that descended the S flank to an 800-m elevation a.s.l. An ash plume drifted W.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

17 June 2009            Back to Top

Three strong eruptions on 16 June resulted in pyroclastic flows. The National Park was evacuated as a precaution, but reopened the next day. Increased degassing the previous week had prompted an elevation of the hazard status to Level 3 (on a scale of 1-4).

Sources: Inside Costa Rica , Tico Times

6 May 2009            Back to Top

OVSICORI-UNA reported that during April activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches that traveled down the SW, S, and N flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

8 April 2009            Back to Top

OVSICORI-UNA reported that during March activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from the fronts of lava flows that traveled down the SW flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

11 March 2009            Back to Top

OVSICORI-UNA reported that during February, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts that traveled down the SW flanks. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

11 February 2009            Back to Top

OVSICORI-UNA reported that during January, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts that traveled down the SW flanks. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

24 September 2008            Back to Top

OVSICORI-UNA reported that changes in morphology and the health of vegetation at Arenal were documented during approximately 14-20 September. Fine ashfall produced at the summit by an active lava flow impacted and burned vegetation along the upper and lower E and NE flanks. The impact on the vegetation was more severe near the summit. By mid September, additional material moving down the SW flank had filled the 6 June collapse scar and built an 800-m-high levee. Occasional incandescent blocks roll down the top of the levee. Material accumulated on both sides of the levee and at the distal end, creating a 200-m-wide fan. A mass of material also accumulated at the SW edge of the summit, causing blocks to occasionally roll down the N flank.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

10 September 2008            Back to Top

OVSICORI-UNA reported that during August, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts that traveled down the SW flanks. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

4 June 2008            Back to Top

OVSICORI-UNA reported that an incandescent avalanche descended Arenal's SW flank on 6 June producing an 800-m-long scar and depositing a wide debris fan at the base of the volcano. A plume of dust, ash, and gas drifted W and NW, depositing fine ash in a small area downwind. The plume panicked tourists and park rangers 2 km away to the W. The park was immediately closed for the day and the tourists were evacuated. According to a news article, another incandescent avalanche descended the SW flank on 10 June and generated an ash plume. Authorities evacuated people in the area.

Sources: La Nacion , Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

16 April 2008            Back to Top

In March, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts that traveled down the SW flanks. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

6 February 2008            Back to Top

In January, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts that traveled down the S flanks. Blocks from the lava-flow fronts periodically reached vegetation and started small fires. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

9 January 2008            Back to Top

In December, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts that traveled down the SW flank. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

5 December 2007            Back to Top

In November, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling down the S flank, and occasional avalanches from lava-flow fronts. Blocks from near the edge of the crater rolled down the SE and SW flanks. Volcanic activity was at relatively low levels and few eruptions occurred. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

19 September 2007            Back to Top

Based on initial observations from park visitors and resort personnel, OVSICORI-UNA reported that a pyroclastic flow from Arenal traveled W on 18 September. The event was recorded by a local seismic station.

Based on field observations, a scientist from Instituto Costarricense de Electricidad (ICE) reported that multiple pyroclastic flows traveled S an approximate distance of 1 km on 18 September. Explosions occurred that occasionally produced ash. Small avalanches were noted and one larger avalanche on the S flank was incandescent. Avalanche activity continued on 19 September.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) , Instituto Costarricense de Electricidad (ICE)

5 September 2007            Back to Top

In August, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling down the SW and S flanks, and occasional avalanches from lava-flow fronts. Volcanic activity was at relatively low levels and few eruptions occurred. Blocks from the lava-flow fronts periodically reached vegetation and started small fires. Acid rain and small amounts of ejected pyroclastic material affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Pyroclastic cones on the NE and SW flanks continued to grow. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

8 August 2007            Back to Top

In July, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling SW and S, and occasional avalanches from lava-flow fronts. Blocks from the lava-flow fronts periodically reached vegetation and started small fires. Volcanic activity was at relatively low levels and few eruptions occurred. Small amounts of pyroclastic material were ejected and affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Ash and acid rain fell on the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

20 June 2007            Back to Top

In May, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling SW, and occasional avalanches from lava-flow fronts. Blocks from the lava-flow fronts periodically reached vegetation and started small fires. Volcanic activity was at relatively low levels and few eruptions occurred. Small amounts of pyroclastic material were ejected and affected the NE and SE flanks. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Ash and acid rain fell on the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

7 March 2007            Back to Top

In February, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling N, and occasional avalanches from lava-flow fronts. Blocks from the lava-flow fronts traveled N, NE, and NW, periodically reaching vegetation where they started small fires. Volcanic activity was at relatively low levels, however, with few eruptions occurring and a small amount of pyroclastic material ejected. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Ash and acid rain fell on the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

18 October 2006            Back to Top

In September, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling N, and occasional avalanches from lava-flow fronts. Blocks from the lava-flow fronts traveled N, NE, and NW, periodically reaching vegetation where they produced small fires. Volcanic activity was at relatively low levels, however, with few eruptions occurring and a small amount of pyroclastic material ejected. Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Ash and acid rain fell on the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

6 September 2006            Back to Top

In August, activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, lava flows traveling N, and occasional avalanches from lava-flow fronts. Volcanic activity was at relatively low levels, however, with few eruptions occurring and a small amount of pyroclastic material ejected. Eruptions produced ash plumes that rose ~500 m above the crater (~7,100 ft a.s.l.). Ash and acid rain fell on the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. Crater D showed only fumarolic activity.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

9 August 2006            Back to Top

In July, activity from Arenal's Crater C consisted of lava flows traveling N, gas emission, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts. Volcanic activity was at low levels, with few eruptions occurring and a small amount of pyroclastic material ejected. Eruptions produced ash plumes that rose ~500 m above the crater (or 7,100 ft a.s.l.). Ash and acid rain fell on the NE and SE flanks. Small avalanches of volcanic material traveled down several ravines. There was only fumarolic activity at Crater D.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

10 May 2006            Back to Top

On 10 May around 1000, a pyroclastic flow traveled down Arenal's N flank. An ash-and-gas cloud was produced that drifted SW.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

29 March 2006            Back to Top

OVSICORI reported that on 2 April around 1000 a small pyroclastic flow traveled down Arenal's W flank.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

8 March 2006            Back to Top

In February, activity at Arenal's Crater C consisted of lava flows traveling SW and W, gas emission, sporadic Strombolian eruptions, and occasional avalanches from lava-flow fronts. Volcanic activity was at low levels, with few eruptions occurring and a small amount of pyroclastic material ejected. Eruptions produced ash plumes that rose ~500 m above the crater (or 7,100 ft a.s.l.). Ash and acid rain fell on the NE, E, and SE flanks. Small avalanches of volcanic material traveled down several ravines. There was only fumarolic activity at Crater D.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

2 November 2005            Back to Top

Explosive activity began at Arenal on 2 November at 1454. A pyroclastic flow was generated at 1502 and movement continued for ~10 minutes. During a visit to the volcano the next day, OVISICORI-UNA scientists found that the mid-sized pyroclastic flow traveled down the volcano's W flank, producing an ash cloud that drifted SE. An area was impacted that extended from the volcano's summit to about 1,000 m a.s.l. on Arenal's W flank. The pyroclastic flow occurred in an area that is closed to visitors. During the previous several months lava flows on the volcano's SW flank had been growing rapidly.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

7 July 2004            Back to Top

Since an eruption during the evening of 6 July sent an avalanche of lava cascading down the side of Arenal volcano, no subsequent activity has been reported. According to news reports, on 7 July, Costa Rica's National Emergency Commission (CNE) issued an alert and prohibited people from approaching the volcano.

Sources: Agence France-Presse (AFP)

3 September 2003            Back to Top

A sequence of pyroclastic flows began at Arenal on 5 September at 1055. Seismographs recorded eight signals within 2 hours after the activity began. Lava flows descended to 800 m down the volcano's N and NE flanks. Ash drifted towards the W and NW. No injuries or deaths were reported and the main effects were limited to the National Park boundaries.

Sources: Associated Press , Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) , Reuters

8 January 2003            Back to Top

During December activity at Arenal consisted of continuous gas emissions, lava flows towards the W flank, and sporadic Strombolian eruptions. In addition, fumarolic activity occurred at Crater D.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

28 March 2001            Back to Top

On 29 March OVSICORI-UNA personnel visited the area affected by pyroclastic flows that traveled down the flanks of Arenal on 24, 25, and 26 March. The pyroclastic-flow deposits were located on the N and NE flanks of the volcano. The ash clouds produced from the pyroclastic flows drifted towards the W and SW, depositing ash on an area up to 10 km2 including two towns. Some of the block-and-ash deposits were several meters thick and the debris fan was up to 250 m wide. There were no reports of injuries or damage to buildings.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

21 March 2001            Back to Top

OVSICORI-UNA reported on 26 March that at least three pyroclastic-flow episodes occurred on 24 March between 1234 and 1342. Unlike previous pyroclastic flows, these descended the W flank. National Park guards observed the resulting ash clouds moving SW. There were no reports of injuries or damage.

Sources: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

Below is a summary of eruption dates and Volcanic Explosivity Indices (VEI).

The following references are the sources used for data regarding this volcano. References are linked directly to our volcano data file. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title. Additional discussion of data sources can be found under Volcano Data Criteria.

Alvarado G E, 1989. {Los Volcanes de Costa Rica}. San Jose, Costa Rica: Universidad Estatal a Distancia, 175 p

Alvarado G E, 2000. {Volcanes de Costa Rica: su geologia, historia y riqueza natural}. San Jose, Costa Rica: EUNED, 269 p

Alvarado G E, Soto G J, 2002. Pyroclastic flow generated by crater-wall collapse and outpouring of the lava pool of Arenal volcano, Costa Rica. {Bull Volc}, 63: 557-568

Alvarado G E, Soto G J, 2008. Volcanoes in the pre-Columbian life, legend, and archaeology of Costa Rica (Central America). {J Volc Geotherm Res}, 176: 356-362

Alvarado G E, Soto G J, Schmincke H-U, Blge L L, Sumita M, 2006. The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica. {J Volc Geotherm Res}, 157: 9-33

Alvarado-Induni G E, 2005. {Costa Rica, Land of Volcanoes}. San Jose, Costa Rica: EUNID, 306 p

Barquero-H J, Saenz-R R, 1987. Aparatos volcanicos de Costa Rica. {Heredia, Costa Rica: OVSICORI-UNA}, 1:750,000 map and volcano list

Bolge L L, Carr M J, Feigenson M D, Alvarado G E, 2006. Geochemical stratigraphy and magmatic evolution at Arenal volcano, Costa Rica. {J Volc Geotherm Res}, 157: 34-48

Bolge L L, Carr M J, Feigenson M D, Borgia A, 2004. Geochemistry and magmatic evolution of explosive tephras ET3 and ET4 from Arenal volcano, Costa Rica. {Rev Geol Amer Central}, 30: 127-135

Borgia A, Poore C, Carr M J, Melson W G, Alvarado G E, 1988. Structural, stratigraphic, and petrologic aspects of Arenal-Chato volcanic system, Costa Rica: evolution of a young stratovolcanic complex. {Bull Volc}, 50: 86-105

Carr M J, 1984. Symmetrical and segmented variation of physical and geochemical characterisitics of the Central American volcanic front. {J Volc Geotherm Res}, 20: 231-252

Chiesa S, 1987. La mayor erupcion pliniana del Volcan Arenal, Costa Rica. {Rev Geol Amer Central}, 6: 25-41

Cigolini C, Borgia A, Casertano L, 1984. Intra-crater activity, aa-block lava, viscosity and flow dynamics; Arenal Volcano, Costa Rica. {J Volc Geotherm Res}, 20: 155-176

Cole P D, Fernandez E, Duarte E, Duncan A M, 2005. Explosive activity and generation mechanisms of pyroclastic flows at Arenal volcano, Costa Rica between 1987 and 2001. {Bull Volc}, 67: 695-716

Fudali R F, Melson W G, 1972. Ejecta velocities, magma chamber pressure and kinetic energy associated with the 1968 eruption of Arenal volcano. {Bull Volc}, 35: 383-401

Ghigliotti M, Frullani A, Alvarado G E, Soto G J, 1991. Distribucion areal y caracteristics de los depositos de tefra mas recientes (1080-1968 dC). Bol Obs Vulc Arenal 4(8): 11-33

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. {IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior}.

Melson W G, 1984. Prehistoric eruptions of Arenal volcano, Costa Rica. {Vinculos}, 10: 34-59

Melson W G, 1994. The eruption of 1968 and tephra stratigraphy of Arenal Volcano. {In}: Sheets P D, McKee B R (eds) {Archaeology, Volcanism, and Remote Sensing in the Arenal Region, Costa Rica}, Austin, TX: Univ Texas Press, p 24-47

Melson W G, Saenz R, 1973. Volume, energy and cyclicity of eruptions of Arenal volcano, Costa Rica. {Bull Volc}, 37: 416-437

Oppenheim V, 1970. Eruption of Arenal, Costa Rica. {Texas J Sci}, 22: 88-90

Reagan M K, Gill J B, Malavassi E, Garcia M O, 1987. Changes in magma composition at Arenal Volcano, Costa Rica, 1968-1985; real-time monitoring of open-system differentiation. {Bull Volc}, 49: 415-434

Sheets P D, McKee B R, 1994. {Archaeology, volcanism, and remote sensing in the Arenal region, Costa Rica}. Austin, TX: Univ Texas Press, 350 p

Smithsonian Institution-GVN, 1990-. [Monthly event reports]. {Bull Global Volc Network}, v 15-33

Soto G J, Alvarado G E, 2006. Eruptive history of Arenal volcano, Costa Rica, 7 ka to present. {J Volc Geotherm Res}, 157: 254-269

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Soto G J, Alvarado G E, Madrigal L A, 1996. Las posibles erupciones del Volcan Arenal en 1915 y 1922. {Bol Obs Vulc Arenal}: 6: 45-52

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Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. Arenal's most recent eruptive period began with a major explosive eruption in 1968. Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank.