Pyroclastic shield
shield volcano
In volcanology, a pyroclastic shield or ignimbrite shield is an uncommon type of shield volcano. Unlike most shield volcanoes, pyroclastic shields are formed mostly of pyroclastic and highly explosive eruptions rather than relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano.
They typically display low-angle flank slopes and often have a central caldera caused by large eruptions. Lava is commonly extruded after explosive activity has ended. The paucity of associated Plinian fall deposits indicates that pyroclastic shields are characterized by low Plinian columns.
Pyroclastic shields are commonly known to form in the Central Andes of South America, as well as in Melanesia (the island of Bougainville alone has two). There are also pyroclastic shields in Africa, such as Emi Koussi in Chad.
Examples
Ambrym, Vanuatu
Apoyeque, Nicaragua
Masaya, Nicaragua
Billy Mitchell, Bougainville, Papua New Guinea
Emi Koussi, Chad
Laguna Colorada, Bolivia
Loloru, Bougainville, Papua New Guinea
Cerro Panizos, Bolivia
Purico Complex, Chile
Rabaul Volcano, New Britain, Papua New Guinea
Sacabaya, Bolivia
Mount Shiribetsu, Hokkaido, Japan
Tata Sabaya, Bolivia
Taal Volcano, Philippines
Hofsjökull, Iceland - initially built from basaltic lava, but may have transitioned to highly viscous lava.
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