[2] Mount Pinatubo's volcanic activity has followed a cycle: centuries of repose terminated by a caldera-forming eruption with large pyroclastic flows; a post-eruption aftermath of rain-triggered lahars in surrounding drainages and dome-building that fills the caldera; and then another long quiescent period.

Experts had feared the weight of the water could have breached the crater walls and flooded the homes of up to 40,000 people in and around the small coastal town of Botolan, located 25 miles from the volcano.

[citation needed] In September 2001, residents of Botolan and nearby areas were sent to evacuation centers as a precaution from a possible deluge of mud and water.

In 2002, accumulated rainwater in the lake rose to dangerous levels during the rainy monsoon season, breached the artificial drainage canal, and triggered mild lahar flows in the area.

Eventually, a trail called the Skyway was made that allows 4 wheel drive vehicles a shorter route to a drop off point to trek to the crater.