The Yarrabubba 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 crater ...

, situated in the northern

Yilgarn Craton The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have b ...

near Yarrabubba Station between the towns of

Sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

and Meekatharra,

Mid West The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four Census Bureau Region, census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of ...

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

.Macdonald F.A., Bunting J.A. & Cina S.E. 2003. Yarrabubba—a large, deeply eroded impact structure in the Yilgarn Craton, Western Australia. Earth and Planetary Science Letters 213, 235–247
Abstract
/ref>Bunting J.A. & Macdonald F.A. 2004. The Yarrabubba structure, Western Australia—clues to identifying impact events in deeply eroded ancient cratons. Geological Society of Australia Abstracts 73, 227. With an age of 2.229 billion years, it is the oldest known impact structure on Earth.

Description

While the rim of original crater has been completely eroded and is not readily visible on aerial or satellite images, it is centered on a feature called the Barlangi Rock. The evidence for the extent of impact comes from the presence of

shocked quartz Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal. These pl ...

and

shatter cone Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions. They are evidence that the rock has been subjected to a shock with pressures in the rang ...

s in outcrops of

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

interpreted to be near the centre of the original crater, and from

geophysical Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' some ...

data. The diameter of the original crater is uncertain, but has been estimated to be from . Computer simulations of a in diameter impactor crashing into a thick ice sheet covering granite bedrock produced a crater of final diameter compatible with the Yarrabubba crater.

Age

The impact has been dated to 2,229±5 million years ago, making it the world's oldest confirmed impact structure. This date places the impact in the early

Rhyacian The Rhyacian Period (; grc, ῥύαξ, translit=rhýax, meaning "stream of lava") is the second geologic period in the Paleoproterozoic Era and lasted from Mya to Mya (million years ago). Instead of being based on stratigraphy, these dates are ...

, around the end of the

Huronian glaciation The Huronian glaciation (or Makganyene glaciation) was a period where several ice ages occurred during the deposition of the Huronian Supergroup, rather than a single continuous event as it is commonly misrepresented to be. The deposition of th ...

. The age finding was based on analysis of ancient crystals of the minerals

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...

and

monazite Monazite is a primarily reddish-brown phosphate mineral that contains rare-earth elements. Due to variability in composition, monazite is considered a group of minerals. The most common species of the group is monazite-(Ce), that is, the ceriu ...

found in the crater. Scientists used uranium-lead dating to analyze the samples and to determine the age of the impact crater.Oldest impact crater on Earth found and it could throw light on ancient climate change
Rob Waugh, Yahoo News UK, January 21, 2020.

References

External links

Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognised meteorite impact structure
Timmons M. Erickson, Christopher L. Kirkland, Nicholas E. Timms, Aaron J. Cavosie & Thomas M. Davison, January 21, 2020. Nature Communications volume 11. {{Impact cratering on Earth Impact craters of Western Australia Proterozoic impact craters Precambrian Australia Mid West (Western Australia)

Description

Age

See also

References

External links