Famous Volcanoes in the World_Study on Mount Pinatubo

Mount Pinatubo is an active stratovolcano in the Zambales Mountains, situated on the tripoint border of the Philippine provinces of Zambales, Tarlac, and Pampanga, all of which are in Central Luzon on the northern island of Luzon.  Most people were unaware of its eruptive history until the pre-eruption volcano activity in early 1991. Pinatubo had been badly eroded and was hidden from view by lush trees that housed a community of several hundred indigenous Aetas.

Pinatubo is well known for its VEI-6 eruption on June 15, 1991, which was the second-largest land eruption of the twentieth century after the Novarupta eruption in Alaska in 1912. Eruption was followed by  typhoon Yunya , delivering a fatal mix of ash and rain to towns and cities near the volcano, complicating the eruption. Predictions of the epic eruption’s commencement resulted in the escape of people from the surrounding areas, sparing countless lives. Tephra surges badly impact surrounding regions, pyroclastic falls, and, later, flooding lahars produced by precipitation remobilisation of older volcanic deposits. This resulted in massive infrastructure devastation and modified waterways for years following the eruption. Minor dome-forming eruptions within the caldera lasted from 1992 until 1993.

The Volcanic Event

Pinatubo erupted on June 15 at around 1:42 p.m. local time, the greatest volcanic eruption since Alaska’s Novarupta in 1912. Its ash cloud included 5 cubic kilometres of material and rose to a height of 40 kilometres. Because a passing typhoon delivered torrential rainfall at the same time, fast-moving streams of ash, mud and volcanic ash known as lahars surged down the volcano, destroying communities, crashing through forests and drowning farmlands and sugarcane plantations. The falling ash mingled with the water, forming a cement-like consistency, and several buildings fell in due to the weight. During the eruption, over 350 people died, the majority as a result of falling roofs.

Pinatubo’s effects did not cease on that day 25 years ago. For the next year, the ash plume’s gas disrupted weather patterns and muted the impacts of global warming. More than a decade later, lahars, which may rush down the mountain after rainstorms, posed a threat to local residents. The explosion of Mount Pinatubo broke new ground, both physically and metaphorically. 

The eruption’s timeline

• On June 12, a tiny boom at 03:41 PST signalled the start of a new, more intense phase of an eruption. 
• A few hours later, enormous explosions lasting about half an hour formed gigantic eruption columns that swiftly reached heights of about 19 kilometres (62,000 feet) and caused significant pyroclastic surges that extended up to four kilometres (2.5 miles) from the summit in certain river basins. 
• A 15-minute outburst 14 hours later propelled volcanic materials to heights of 24 km (15 mi). Volcanic lightning erupted as a result of friction in the speeding ash column.
• After an intensive two-hour swarm of minor earthquakes, a third big eruption erupted at 08:41 on June 13. 
• It lasted around 5 minutes, as the eruption column reached 24 km again (15 mi). After three hours of inactivity, seismic activity resumed and intensified over the next twenty-four hours, culminating in a three-minute eruptive outburst that formed a 21 km (13 mi) high explosion column at 13:09 on June 14.
• Tephra fall from such four big eruptions was widespread to the volcano’s southwest. 2 hours after the last of these 4 explosions, a sequence of eruptions began that lasted twenty-four hours, producing significantly greater pyroclastic flows and surges that travelled several kilometres into river basins on the volcano’s flanks.
• In such eruptions and the subsequent climactic event, dacite was the main igneous rock that made up the tephra. 
• The most frequent phenocryst minerals were hornblende and plagioclase, although an unusual phenocryst mineral named anhydrite was also found. 
• The dacite magma was more oxidised than other magmas, and the sulphur-rich eruption was most likely caused by the redox condition.
• The massive eruption of Mount Pinatubo was seen from Japan’s GMS-4 meteorological satellite
• Mount Pinatubo’s final and climactic eruption began on June 15 at 13:42 PST. The collapse of the top and the formation of a caldera 2.5 km (1.6 mi) in diameter produced multiple significant earthquakes, decreasing the peak from 1,745 m (5,725 ft) to 1,485 m. (4,872 ft).

 Conclusion:

Pinatubo triggered high-speed pyroclastic flow avalanches and clouds of volcanic ash hundreds of miles broad. Meanwhile, when Typhoon Yunya passed within 75 kilometres of the volcano during the eruption’s peak activity, it brought cascading dangers such as floods and fast-moving lahars.