After 600 years of silence, suddenly in 1991, with only minimal warnings, the volcano erupted in all its fury throwing ashes and pyroclastic materials as much as 50,000 ft. into the atmosphere. Now considered the biggest eruption of the 20th century, Mt. Pinatubo has fallen back to sleep, having left spectacular lahar formations. You may choose either to hike up to the crater lake (3 hrs one way) or use the 4x4 jeep nearly all the way up and hike up and down the last 40 minutes only (one way).