Arenal to left and Cerro Chato to right. The barren region in foreground was rainforest until destroyed in 1968 by a directed blast from Arenal
Before 1968 Arenal was a symmetrical cone. Since the 1968 eruption, the first in recorded history, the volcano has continuously produced lava flows, making a huge lava field. A new cone, displaced to the south has made Arenal a complex cone. You can trace the old slope of Arenal in this picture and see the the huge, dark grey lava field that has grown just since 1968. A strombolian explosion has just risen from the active vent.