Deformation (volcanology) in the context of "Mauna Loa"

The 1991 eruption of Mount Pinatubo in the Philippines' Luzon Volcanic Arc was the second-largest volcanic eruption of the 20th century, behind only the 1912 eruption of Novarupta in Alaska. Eruptive activity began on April 2 as a series of phreatic explosions from a fissure that opened on the north side of Mount Pinatubo. Seismographs were set up and began monitoring the volcano for earthquakes. In late May, the number of seismic events under the volcano fluctuated from day-to-day. Beginning June 6, a swarm of progressively shallower earthquakes accompanied by inflationary tilt on the upper east flank of the mountain, culminated in the extrusion of a small lava dome.

On June 12, the volcano's first spectacular eruption sent an ash column 19 km (12 mi) into the atmosphere. Additional explosions occurred overnight and the morning of June 13. Seismic activity during this period became intense. When even more highly gas-charged magma reached Pinatubo's surface on June 15, the volcano exploded, sending an ash cloud 40 km (25 mi) into the atmosphere. Volcanic ash and pumice blanketed the countryside. Huge pyroclastic flows roared down the flanks of Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as 200 m (660 ft) thick. The eruption removed so much magma and rock from beneath the volcano that the summit collapsed to form a small caldera 2.5 km (1.6 mi) across.

The 2018 lower Puna eruption was a volcanic event on the island of Hawaiʻi, on Kīlauea volcano's East Rift Zone that began on May 3, 2018. It is related to the larger eruption of Kīlauea that began on January 3, 1983, though some volcanologists and USGS scientists have discussed whether to classify it as a new eruption. Outbreaks of lava fountains up to 300 feet (90 m) high, lava flows, and volcanic gas in the Leilani Estates subdivision were preceded by earthquakes and ground deformation that created cracks in the roads.

On May 4, a 6.9 magnitude earthquake hit Puna. By May 27, 2018, 24 fissures had erupted lava in and near the Leilani Estates and Lanipuna Gardens subdivisions. The eruption forced the evacuation of approximately two thousand residents. The Puna Geothermal Venture, which provided one-quarter of the island's electricity, was forced to shut down and was later damaged by lava. The fissures had sent lava rivers that buried part of Hawaii Route 137 on May 19, and began flowing into the ocean.

A sector collapse or lateral collapse is the structural failure and subsequent collapse of a minimum volume of 1 km (0.24 cu mi) of a volcano. Unlike smaller flank collapses, a sector collapse can involve the central volcanic pipe and historically this term had been restricted by some writers to such events in arc stratovolcanoes, but is now used for large events in any volcano. Sector collapses are one of the most hazardous volcanic events, often resulting in lateral blasts, landslides, and changes in volcanic eruptive behavior. Sector collapse can be caused by earthquakes, volcanic eruptions, gradual volcanic deformation, and other processes. Sector collapse events can occur on volcanoes at convergent and divergent plate boundaries. Sector collapses are generally very sudden; however, some attempts have been made to predict collapse events.