Caldera CollapseCredit: USGSThe June 15 eruption created a 1.5-mile-wide (2.5 km) collapse caldera (shown here on June 22, 1991) and filled valleys around Pinatubo with pyroclastic-flow deposits. The new summit elevation of Mount Pinatubo dropped from its pre-eruption elevation of 5,725 feet (1,745 meters) above sea level to 4,872 feet (1,485 m).
On June 15, 1991- Mt. Pinatubo (in the Philippines) blew its top again, creating the 2nd. largest volcanic eruption of the 20th. century! The eruption was a VEI-6, & caused high-speed avalanches of hot ash & gas (pyroclastic flows), giant mudflows (lahars), & a cloud of volcanic ash that spanned hundreds of miles across.