At roughly 7:30 a.m. on Monday July 29, 1968–after having lain relatively dormant of over 400 years–Arenal Volcano erupted with violence and fury. Extreme eruptions and volcanic activity continued for several days, killing some 87 persons and burying over 15 square kilometers in rock, lava and ash. In total, the eruptions affected over 232 square kilometers in the surrounding area to varying degrees, with damage to crops, property, livestock and forests.

At the height of this activity the volcano was throwing out massive amounts of lava and ash and tossing giant rocks for distances of up to a mile at speeds of some 600 meters per second.

The explosions formed three new and active craters.

Since that time, Arenal Volcano has maintained nearly constant activity that ranges from soundless explosions with large mushroom-shaped clouds of ash overhead to booming explosions that send hot rocks nearly a kilometer into the air to pyroclastic explosions highlighted by the rush and flow of lava and gasses down the side of the volcano.

Arenal Volcano rises to approximately 1633 meters at its summit, although the exact summit height changes frequently due to the volcanic activity.

The last major eruptions occurred on May 8, 1998 and gave rise to temporary evacuations from area hotels, although the danger quickly passed and no one was injured.