The Popigai impact structure is the eroded remnant of an

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

in northern

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...

, Russia. It is tied with the Manicouagan structure as the fourth largest verified

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 ...

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. A large

bolide A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large crater-forming body, or to one that explodes in the atmosphere. It can be a ...

impact created the diameter crater approximately 35 million years ago during the late

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

epoch (

Priabonian stage The Priabonian is, in the ICS's geologic timescale, the latest age or the upper stage of the Eocene Epoch or Series. It spans the time between . The Priabonian is preceded by the Bartonian and is followed by the Rupelian, the lowest stage of t ...

). It might be linked to the

Eocene–Oligocene extinction event The Eocene–Oligocene extinction event, also called the Eocene-Oligocene transition or ''Grande Coupure'', is the transition between the end of the Eocene and the beginning of the Oligocene, an extinction event and faunal turnover occurring betwe ...

. The structure is east from the outpost of Khatanga and northeast of the city of

Norilsk Norilsk ( rus, Нори́льск, p=nɐˈrʲilʲsk, ''Norílʹsk'') is a closed city in Krasnoyarsk Krai, Russia, located south of the western Taymyr Peninsula, around 90 km east of the Yenisey River and 1,500 km north of Krasnoyarsk. Norilsk i ...

, NNE of the Anabar Plateau. It is designated by

UNESCO The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations (UN) aimed at promoting world peace and security through international cooperation in education, arts, sciences and culture. It ...

as a

Geopark A geopark is a protected area with internationally significant geology within which sustainable development is sought and which includes tourism, conservation, education and research concerning not just geology but other relevant sciences. In 20 ...

, a site of special geological heritage. There is a small possibility that the Popigai impact crater may have formed simultaneously with the approximately 35-million-year-old

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the ...

and Toms Canyon impact craters. For decades, the Popigai impact structure has fascinated

paleontologists Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

and

geologists A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...

, but the entire area was completely off limits because of the diamonds found there. However, a major investigatory expedition was undertaken in 1997, which greatly advanced understanding of the structure. The impactor in this event has been identified as either an diameter

chondrite A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primi ...

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

, or a diameter stony asteroid. The shock pressures from the impact instantaneously transformed

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...

in the ground into

diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...

s within a radius of the impact point. These diamonds are usually in diameter, though a few exceptional specimens are in size. The diamonds inherited the tabular shape of the original graphite grains and also the original crystals' delicate

striation Striations means a series of ridges, furrows or linear marks, and is used in several ways: * Glacial striation * Striation (fatigue), in material * Striation (geology), a ''striation'' as a result of a geological fault * Striation Valley, in Ant ...

Diamond deposits

Most modern industrial diamonds are produced synthetically. The diamond deposits at Popigai have not been mined because of the remote location and lack of infrastructure, and are unlikely to be competitive with synthetic diamonds. Many of the diamonds at Popigai contain

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

lonsdaleite Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice, as opposed to the cubical lattice of conventional diamond. It is found i ...

, an

allotrope of carbon Carbon is capable of forming many allotropes (structurally different forms of the same element) due to its valency. Well-known forms of carbon include diamond and graphite. In recent decades, many more allotropes have been discovered and rese ...

that has a hexagonal lattice. Pure, laboratory-created lonsdaleite is up to 58% harder than ordinary diamonds. * These types of diamonds are known as "impact diamonds" because they are thought to be produced when a meteorite strikes a graphite deposit at high velocity. They may have industrial uses but are unsuitable as

gem A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, a ...

s. Additionally, carbon polymorphs, a combination of diamond and lonsdaleite even harder than pure lonsdaleite, have been discovered in the crater.

References

External links

Earth Impact Database

About the Popigai impact structure

UNESCO Global Geopark Network

Google Maps
{{Authority control Impact craters of Russia Impact craters of the Arctic Eocene impact craters Priabonian Stage Landforms of Krasnoyarsk Krai Diamond mines in Russia Diamond mines in the Soviet Union

Diamond deposits

See also

References

External links