Billy Mitchell is a

pyroclastic shield 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 basalt ...

, an uncommon type of volcano in the central part of the island of Bougainville, just north-east of the Bagana Volcano in

Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

. It is a small

truncated by a 2 km wide

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

filled by a

crater lake Crater Lake ( Klamath: ) is a volcanic crater lake in south-central Oregon in the Western United States. It is the main feature of Crater Lake National Park and is a tourist attraction for its deep blue color and water clarity. T ...

. It is generally thought to be named after

Billy Mitchell William Lendrum Mitchell (December 29, 1879 – February 19, 1936) was a United States Army officer who had a major role in the creation of the United States Air Force. Mitchell served in France during World War I and, by the conflict's end, ...

, a 20th-century

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

Army An army, ground force or land force is an armed force that fights primarily on land. In the broadest sense, it is the land-based military branch, service branch or armed service of a nation or country. It may also include aviation assets by ...

general who is sometimes regarded as the father of the

United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...

, although the exact origin of this claim is not known.

Background

The last two major eruptions were in 1580 AD ± 20 years and about 1030 AD. They were among the largest

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

eruptions in Papua New Guinea. Both were

explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...

s with a

Volcanic Explosivity Index The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982. Volume of products, eruption c ...

of at least 5. The 1580 AD ± 20 years eruption produced

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...

s and probably formed its

. The second of these eruptions likely had an effect on worldwide temperature, lowering it by 0.2-0.3 degrees celsius for a year or two after the event. The

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...

deposit from that eruption, which had a VEI of 6, extends from the caldera to the coast, and its volume is around . The volcano is considered dormant as its last eruption was over 350 years ago.

Caldera lake

Billy Mitchell caldera lake is about 1,013 m above sea level, has a total surface area of , and the maximum depth approximately 88.3 m. The only fish species in the lake is the eel Anguilla megastoma. Robert Schabetsberger, Ursula Sichrowsky, Alexander Scheck, Michael Schagerl, Barbara Mähnert, Bettina Sonntag, Karin Pal
First Limnological Characterization of Crater Lake Billy Mitchell (Bougainville Island, Papua New Guinea)
Pacific Science, 71(1):29-44 (2017). Billy Mitchell lake drains into the Tekan River.

References

External links

Photo of the Billy Mitchell Crater Lake
* {{cite gvp, vn=255011, name=Billy Mitchell, accessdate=2011-11-08 Mountains of Papua New Guinea Volcanoes of Bougainville Island Lakes of Papua New Guinea Pyroclastic shields Volcanic crater lakes VEI-6 volcanoes 16th-century volcanic events Shield volcanoes of Papua New Guinea

Background

Caldera lake

See also

References

External links