Returning to Sta. Juliana
photo by Storm Crypt on Flickr
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This ain't no martian terrain, nor something out of the natural arches landscape in the western United States. This is close to the starting point of the Mt. Pinatubo Trail, within the borders of the municipality of Sta. Juliana, Tarlac Province, Philippines.
Mt. Pinatubo Trail
Sta. Juliana, Tarlac
Philippines
A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.
Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "Plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core-mantle boundary, 3,000 km deep in the Earth.
Mount Pinatubo is an active stratovolcano located on the island of Luzon, near the tripoint of the Philippine provinces of Zambales, Tarlac, and Pampanga. It is located in the Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is 42 km (26 mi) west of the dormant and solitary Mount Arayat. Before 1991, the mountain has no recorded historical eruptions. It was heavily eroded, inconspicuous and obscured from view. It was covered with dense forest which supported a population of several thousand indigenous people, the Aeta, who had fled to the mountains from the lowlands during the Spanish conquest of the Philippines.
The volcano's Plinian / Ultra-Plinian eruption on June 15, 1991 produced the second largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in the Alaska Peninsula. The colossal 1991 eruption had a Volcanic Explosivity Index (VEI) of 6, and came some 450–500 years after the volcano's last known eruptive activity (estimated as VEI 5, the level of the 1980 eruption of Mount St. Helens), and some 1000 years after previous VEI 6 eruptive activity. A VEI of 6 corresponds to 10 to 100 cubic km of released material (Pinatubo released an estimated 6 to 16 cubic km of ash). Successful predictions of the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later by lahars caused by rainwater remobilizing earlier volcanic deposits; thousands of houses and other buildings were destroyed.
The Philippines i/ˈfɪlɨpiːnz/ (Filipino: Pilipinas [ˌpɪlɪˈpinɐs]), officially known as the Republic of the Philippines (Filipino: Republika ng Pilipinas), is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam. The Sulu Sea to the southwest lies between the country and the island of Borneo, and to the south the Celebes Sea separates it from other islands of Indonesia. It is bounded on the east by the Philippine Sea. Its location on the Pacific Ring of Fire and its tropical climate make the Philippines prone to earthquakes and typhoons but have also endowed the country with natural resources and made it one of the richest areas of biodiversity in the world. An archipelago comprising 7,107 islands, the Philippines is categorized broadly into three main geographical divisions: Luzon, Visayas, and Mindanao. Its capital city is Manila.
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