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Small Bodies: Asteroids and Meteoroids
Published in Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice, Solar System, 2021
Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice
Many meteorites seem to have come from differentiated bodies. They are usually made of rock or metal although a small population that consists of both rock and metal is known. Until the 20th century, most meteorites collected were largely made of dense metal even though rocky meteorites are more common. A dark, unusually heavy-to-lift object lying on the ground garners more attention than a rocky meteoroid, which may be overlooked as just one more terrestrial rock. The iron dagger buried with Tutankhamun 〈circa 1341–1324 BCE〉. a pharaoh of Egypt's 18th dynasty, appears to have been made from a meteorite. Antarctica is a good place to look for meteorites because of their contrasting appearance against the blue ice and because the movements of the ice sheets tend to concentrate meteorites in specific areas.
The Origin of the Elements and Earth
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
The planetesimals in the inner solar system collided and coalesced into a few larger protoplanets and eventually became the planets we have today, but because the distinction between planetesimals, protoplanets, and true planets is a hazy one, the timing of these events is hard to say with certainty. Scientists have estimated the age of the solar system by studying the ages of meteorites, because meteorites are believed to be the oldest material in the solar system. The oldest meteorites are about 4.55 billion years old, and consequently Earth’s age is estimated at 4.55 billion years. However, the oldest rocks on Earth are only 3.8 billion years old, although some individual mineral grains are 4.4 billion years old.
The geological origin of building stones
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
The oldest dated Earth minerals (4.0–4.2 billion years old) are small zircon crystals, originally formed in magmas, which are found in the sedimentary rocks of Western Australia. The oldest Moon rocks are from the lunar highlands and were formed when the early lunar crust was partially or entirely molten, dated at between 4.4–4.5 billion years in age. The majority of meteorites have ages of 4.4–4.6 billion years; these meteorites are fragments of asteroids and represent some of the most primitive material in the solar system. The evidence from radiometric dating indicates that Earth is about 4.54 billion years old. Thus, Figure 2.10(a) provides an overall history of the Earth via the clock-type diagram and indicates that the building stones discussed in this book, although millions of years old, were all actually formed relatively late in the Earth’s life, i.e., just from 10 o’clock to 12 o’clock. This latter duration has been sub-divided into various eras, periods and epochs of time, as shown in the time charts in both Figures 2.10(a) and (b).
Geoheritage and Geoconservation in Australia
Published in Australian Journal of Earth Sciences, 2019
In Australia, there are many sites considered to be geological monuments, or sites of geological significance, although this does not necessarily ensure their protection. Many of the known sites of geological significance in Australia reside in National Parks, World Heritage areas, are locations specifically dedicated to the conservation of geological values, have been inscribed as National Parks specifically for their landscape or geology (Australian Academy of Science, 1968), or are locations that have had geological features as part of their criteria for inscription as World Heritage sites. These include: Gosses Bluff meteorite impact crater in the NT; the Wolfe Creek meteorite impact crater in WA; Purnululu (the Bungle Bungles) in WA; the Gogo Fish fossil site in the Kimberleys, WA; Geikie Gorge National Park in WA; Windjana Gorge National Park in WA; the Ediacara Fauna site in the Flinders Ranges, SA; Undara Volcanic National Park in Queensland; the Chillagoe Limestone Karst area in Queensland; and Hallett Cove in SA, among others.
Meteorite crater re-interpreted as iceberg pit in west-central Sweden
Published in GFF, 2021
Christian Öhrling, Henrik Mikko, Gustaf Peterson Becher, Carl Regnéll
During a geomorphological mapping project in Härjedalen, we recognized numerous landforms which we interpret as iceberg pits and plough marks formed in early Holocene glacial lakes. In this study, we focus on the depression at Torbygget and suggest that it is an iceberg-scouring mark, not a meteorite-impact crater.