Butcher Ridge () is a large, mainly ice-free ridge near the polar plateau in the west part of the Cook Mountains. The ridge is in the form of an arc, extending northwest from Mount Ayres.Faure, G., and Mensing, T. M., 2010. ''The Transantarctic Mountains Rocks, Ice, Meteorites and Water.'' Germany, Heidelberg, Springer Dordrecht. 804 pp. The Ridge peaks at 2,003 meters (6,572 feet). It was named by the

Advisory Committee on Antarctic Names The Advisory Committee on Antarctic Names (ACAN or US-ACAN) is an advisory committee of the United States Board on Geographic Names responsible for recommending commemorative names for features in Antarctica. History The committee was established ...

for Commander H.K. Butcher,

U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Department of Defense. It is the world's most powerful navy with the largest displacement, at 4.5 million tons in 2021. It has the world's largest aircraft ...

, air operations officer on the Staff of the U.S. Naval Support Force, Antarctica, during U.S. Navy Operation Deepfreeze 1963 and 1964.

Geology

Butcher Ridge is a deeply eroded

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the g ...

igneous intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

. It consists of a

hypabyssal A subvolcanic rock, also known as a hypabyssal rock, is an intrusive igneous rock that is emplaced at depths less than within the crust, and has intermediate grain size and often porphyritic texture between that of volcanic rocks, which are extr ...

intrusion that contains rhythmically layered glassy rocks and

plutonic Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: Marc ...

rocks that vary in composition from

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

." U-Pb dating of

baddeleyite Baddeleyite is a rare zirconium oxide mineral (ZrO2 or zirconia), occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high Index of refraction, indices of refraction, and ranges from colorless to yel ...

from the Butcher Ridge yielded an age of about 182.4

Myr Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

. This age confirms that this igneous complex was emplaced contemporaneously with the Ferrar large igneous province.Nelson, D.A., Cottle, J.M. and Schoene, B., 2019. ''Butcher Ridge igneous complex: A glassy layered silicic magma distribution center in the Ferrar large igneous province, Antarctic.'' ''Antarctica. Bulletin'', 132(5-6), pp.1201-1216. Faure and Mensing argue that the glassy and "pseudo-

volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...

" rocks that compose the majority of the Butcher Ridge igneous complex are incompatible with it being a hypabyssal intrusion. Based on this and together with an associated strong

magnetic anomaly In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying ...

and other features, they concluded that the Butcher Ridge igneous complex should be seriously investigated as a possible

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

impact structure An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure. In contrast, an impact crater is the surface e ...

Features

Gjelsvik Spur

. A rock spur northwest of Mount Ayres on the Butcher Ridge, in the Cook Mountains. It was named after Per Gjelsvik of the

University of Wisconsin–Madison The University of Wisconsin–Madison (University of Wisconsin, Wisconsin, UW, UW–Madison, or simply Madison) is a public land-grant research university in Madison, Wisconsin, United States. It was founded in 1848 when Wisconsin achieved st ...

aeromagnetic project under John Behrendt, 1963–64. Working from

aircraft, Gjelsvik acquired aeromagnetic profiles over the

Transantarctic Mountains The Transantarctic Mountains (abbreviated TAM) comprise a mountain range of uplifted rock (primarily sedimentary) in Antarctica which extends, with some interruptions, across the continent from Cape Adare in northern Victoria Land to Coats L ...

bordering the

Ross Sea The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who ...

and

Ross Ice Shelf The Ross Ice Shelf is the largest ice shelf of Antarctica (, an area of roughly and about across: about the size of France). It is several hundred metres thick. The nearly vertical ice front to the open sea is more than long, and between high ...

McCafferty Spur

. A spur on the north face of Butcher Ridge, in the Cook Mountains of Antarctica, northwest of Mount Ayres. It was named after Anne McCafferty, a geophysicist with the

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

(USGS), who in 1991–92 worked on a USGS aeromagnetic survey over the

and, in a cooperative USGS–German project, participated in the first aeromagnetic flight across the Butcher Ridge and Cook Mountains.

References

Sources

* * Ridges of Oates Land {{OatesLand-geo-stub