Relic of ancient asteroid found ..punched 160km-wide (100 miles) hole in the Earth's surface

BBC ^ | Wednesday, 10 May 2006, 17:10 GMT 18:10 UK | Rebecca Morelle BBC News science reporter

[FairOpinion]

"So what kind of catastrophe hit us back then? "


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Whatever it was, but one thing is certain, it's "Bush' fault". That'll drive his approval rating down to 20% for sure.

(Sorry, I just couldn't resist)

[Ernest_at_the_Beach]

That's OK, it's the wee hours, and not many will notice....time to close down for the night,....

[FairOpinion]

I don't normally engage in stupid wise cracks, but as you say, it's late...

It is actually a very interesting article.

I think there were other meteors that actually made it to Earth. Wasn't there a large one that made a huge crater in Russia?

[FairOpinion]

I don't normally engage in stupid wise cracks, but as you say, it's late...

It is actually a very interesting article.

I think there were other meteors that actually made it to Earth. Wasn't there a large one that made a huge crater in Russia?

[Irishguy]

ah yes...helen, she has more chins then a chinese phonebook...

[Ernest_at_the_Beach]

In Russia and also the one in Mexico's Yucatan that did in the dinosaurs....

[gleeaikin]

You are right about diamonds and the volcanic pipes. There has recently been a major diamond find around VPs in Canada north of Yellowknife.

The major crater in Siberia might be Popigai (60 miles in diameter). It and the Chesapeake Crater (50 miles in diameter), running from Norfolk to Exmore on the Delmarva Peninsula, as well as a 9 mile diameter crater off Toms River, NJ, all were formed about 35 million years ago. The age is about the same and they all struck from the same direction and at the same low angle, so it might have been an event like the recent Jupiter extraveganza.

I also suspect that further study may show that the massive Siberian Traps, formed 250 million years ago at the end Permian catastrophic extinction time, could have been formed by a very large boloid and then buried in magma.

Many craters are the source of a varied array of minerals and metals, including oil. The 180 mi. diameter Vredefort crater in South Africa is a major source of gold and uranium. The Sudbury in Ontario, Canada (50 mi. diameter) has many important metals. Some of the oil in Oklahoma and the North Sea has a crater origin. We need to explore more craters and find more craters (and oil, I hope, I hope).

[Exton1]

Its Bushes falut.

[SunkenCiv]

[SunkenCiv]

Manicougan crater / lake:

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[Ernest_at_the_Beach]

Google finds stuff:

Manicougan Crater in Quebec, Canada

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Earth Impact Database

[Ernest_at_the_Beach]

The Earth Impact Database

The Earth Impact Database comprises a list of confirmed impact structures from around the world. The database was conceived in its earliest form when a systematic search for impact craters was initiated in 1955 by the Dominion Observatory, Ottawa, under the direction of Dr. Carlyle S. Beals . This was achieved via the study of over 200,000 aerial photographs of the Canadian Shield. Since that time the list has grown as new craters have been added. When the Dominion Observatory impact group moved to the Geological Survey of Canada (GSC) in the late 1980s, a more formal listing was developed. In 2001, following termination of impact studies at the GSC, the database was transferred to the Planetary and Space Science Centre at the University of New Brunswick, Canada. The site is currently managed by Jason Hines (Data Manager, NASA Regional Planetary Image Facility, Planetary and Space Science Centre) and John Spray (Director, Planetary and Space Science Centre). Major contributions to the development of earlier versions of this database have been made by colleagues Richard Grieve and James Whitehead. We would like users of this site to be aware of its purpose:

The Earth Impact Database is maintained as a not-for-profit source of information to assist the scientific, industrial, government and public communities around the world in furthering our collective knowledge of impact structures on Earth.

We rely heavily on the science community adding to the knowledge base, such that the list is kept as current as possible. In this light, the database is operated on consensus, relying on scientific input from the community at large. The database is thus a dynamic document, with new craters being added as evidence is collected.

The impact structure images have been compiled over many years. They are shown at relatively low resolution, some images are available in higher resolution on request from the Data Manager. A small fee may be charged if the image is to be used for commercial purposes.

Criteria

The principal criteria for determining if a geological feature is an impact structure formed by the hypervelocity impact of a meteorite or comet are listed below. The criteria can be divided into megascopic (overview – bird’s eye / satellite scale), macroscopic (can be seen easily seen with the naked eye) and microscopic (requires a microscope to see) features, as follows:

1. Presence of shatter cones that are in situ (macroscopic evidence).
   
2. Presence of multiple planar deformation features (PDFs) in minerals within in situ lithologies (microscopic evidence).
   
3. Presence of high pressure mineral polymorphs within in situ lithologies (microscopic evidence and requiring proof via X-ray diffraction, etc.).
   
4. Morphometry. On other planetary bodies, such as the Moon and Mars, we rely on the shape of the impact structure to determine its presence and type (simple versus complex, etc.). This is a megascopic quality (i.e., too big to be seen unaided by the humaneye , thus requiring remote sensing, aerial photography, detailed mapping of multiple outcrops to assemble and view the typically km- or multiple km-size structure). On Earth, recognizing impact structures solely by their morphometry is complicated by two factors: (a) weathering, erosion, burial processes and tectonic deformation can obscure and/or destroy the original shape; (b) certain terrestrial features generated by means other than impact can have comparable circular form (e.g., volcanoes, salt diapirs, glacigenic features), such that a circular structure alone is not sufficient to claim impact structure status. Some buried craters have been revealed solely by geophysical techniques, although drill core is typically required to reveal macro- and microscopic evidence to prove an impact origin.
   
5. Presence of an impact melt sheet and/or dikes, and impact melt breccias that were generated due to hypervelocity impact (macroscopic). These bodies typically have a crustal composition derived by the fusion of target rocks (i.e., there is no mantle contribution to the melt). Such meltsmay be contaminated by meteoritic (projectile) components (the latter requires specialized geochemical analysis to detect the projectile components). Melt sheets may be overlain by so-called fallback breccias (referred to as “suevite” by some workers), and material blasted out of the crater may form ejecta blankets about the original central cavity. For large impact events, ejecta can be distributed globally. Impact melt sheets are recognized by careful mapping and rock sampling followed by microscopy and geochemical analysis.
   
6. Pseudotachylyte and Breccias: Pseudotachylyte is a rock type generated by faulting at either microscopic or macroscopic scales. However, pseudotachylytes are also associated with seismic faulting due to endogenic processes (e.g., earthquakes due to isostatic rebound and plate tectonics), so they are not exclusively impact generated. However, in association with features listed above, they can be a contributory criterion. Pseudotachylyte associated with impact structures may form in radial and concentric fault systems that help to define the megascopic structure of the crater. Pseudotachylytes can be included in a family of rocks referred to as breccias. Many different types of breccia can be developed as part of the impact process (including impact melt breccias listed in (5) above), but breccias can also form by endogenic processes. The interpretation of breccias therefore requires considerable care and experience. Moreover, they should not be considered diagnostic of impact, but rather contributory evidence.

In terms of relative importance, it is generally considered that criteria 1-3 above are definitive (they all relate to the passage of a shock wave through rock and resulting modification processes), with contributory evidence being added by 4-6 (which result from secondary effects, such as gravitationally driven crater modification). For buried structures that cannot be directly accessed, but are well-preserved as revealed by detailed geophysical techniques (especially seismic data), some workers consider this as strong evidence in favour of an impact origin. Normally, buried craters are verified by drilling and sampling the material directly for evaluation using criteria 1-3 above.

Caveat

The Earth Impact Database represents a compilation of information from around the world. Maintaining this site is both a formidable task and a formidable responsibility. Moreover, it is a task that is growing because over the last 25 years the impact process has been increasingly appreciated by the Earth Sciences community as an important planet-building and planet-modifying process. A consequence of this is the exponential growth in publications relating to impact. For this reason, we require the cooperation of the geological community in maintaining this site. We ask that specialists notify us of developments relating to impact processes on Earth. Please inform us of relevant publications and abstracts so that we can strive to keep our files and website current. Send information to the attention of :

Jason Hines, Data Manager
Planetary and Space Science Centre
Department of Geology
University of New Brunswick
2 Bailey Drive
Fredericton
New Brunswick E3B 5A3
Canada
Email: jhines@unb.ca
Phone: (506) 453-3560
Fax: (506) 453-5055

[Fred Nerks]

Drilling for Meteorites
By Dan Oancea


A golden meteorite was about to strike the Earth. A huge crowd followed its smoky trail, embarking on a new kind of gold rush. Scientists have gone mad about it too - but all this happened just in the pages of "Hunt for the Meteor", published about 100 years ago by Jules Verne, the visionary founder of Sci-Fi.

Nobody has ever found the golden meteorite, but people have started to realize that some of the giant craters that riddle the scenery could indeed be the result of a real meteor impact. At least this was the opinion of a 1902 Philadelphia mining engineer about a crater that lies in the sands of the Arizona desert surrounded by nickel-iron fragments. Daniel Barringer was the owner of a considerable fortune made by the discovery of silver mines in the Arizona's mountains. Lacking our understanding of high-speed impacts he reasoned that the big chunk of meteoritic iron is still buried deep in the crater. Twenty six years later, after spending his fortune on top of investor's money-about $10 million in today's dollars- the Meteor Crater Exploration and Mining Company stopped working the shafts and galleries that were supposed to lead to a 10 million tons meteorite.

In 1883, a blacksmith identified copper sulphide in the rocks cut by the advancement of the Canadian Pacific railway at Sudbury, Ontario. It later became the Murray Mine. In 1891 a new company was formed to mine the metal: the Canadian Copper Company, a company that soon enough became aware that the mined ore contained a more valuable metal: Nickel. It changed its name in the International Nickel Company (INCO) and today, over 100 years later it still does the very same business mining the richest nickel deposit in the world.

The interpretation of the oval shape structure that hosts the Sudbury deposit generated hot debates, but everything came to an end in 1963, when the U.S. geologist Robert Dietz, which at that time was working for NASA trying to put the first man on the Moon, recognized it as an impact structure. Well, not quite to an end, if we consider that in the early 1960s, Dietz was laughed out of the room at a geological conference when he tried to present its revolutionary theory. Later on, he teamed up with Walter Peredery, a young Canadian geologist and proved them all wrong.

Realizing the potential of impact craters to host mineral ores a new staking rush took place, mostly in North America. In Canada, another famous meteorite crater, the Manicouagan , is explored by daring junior exploration companies like Manicouagan Minerals, Fancamp Exploration and Quinto Technology (find more about their work by accessing InfoMine's comprehensive database).

The Carswell structure of Saskatchewan benefited too from a meteor impact in the Cluff Lake area, where the impact created an uplift of the Athabascan sandstone revealing a number of large unconformity-type uranium deposits. Eso Uranium is carrying out its exploration programs in this area that represents the site of a renowned past producer-the Cogema's Cluff Mine. The above sea level portion of the rim of a huge meteorite impact crater known as the Chicxulub impact crater, located in Mexico has been studied amongst others by Glamis Gold.

The Vredefort impact structure of South Africa well-known for its gold-uranium deposits is intensively mined by different companies.

Lately, Great Australian Resources started investigating the South African Morokweng impact crater, where drilling intercepted high-grade nickel sulphide mineralization. Their confidence has been boasted by a geological report that summarized that all the conditions necessary for the formation of an ore body in impact structures are in place:

- A metal source: the Archaean gneissic basement,
- A concentrating mechanism: homogenization and differentiation through impact induced melting, and
- A trap for the mineralization: brecciated and fractured footwall rocks below the melt sheet.

By the way,if you're planning on visiting France, don't miss the Chateau at Rochechouart that is built from impact breccia material.

A paper called "The formation, morphology, and economic potential of meteorite impact craters" gives us a good idea about the processes involved in a high-speed meteoritic impact, while listing some of the most important deposits of this type.

Now, are we indeed in a shortage of exploration targets?

The authors of "Unraveling the Earth's Geological History from Space using Impact Craters" provide us with a glimpse of the impact craters of our solar system, including the Earth, of course. The paper considers that:

"There are currently about 160 known impact craters on our planet, with diameters ranging from a few hundred meters to several hundred kilometers. This low number is due to the relatively young age and the dynamic nature of the terrestrial geosphere. We also have to take into account the fact that two-thirds of the Earth's surface is covered by oceans, and that the tectonic movements of continental plates, as well as erosion, volcanism and sedimentation processes, have erased and/or hidden most of the original morphological effects of impact-cratering."

According with their map, most of the impact craters are concentrated in the Pre-Cambrian shields, areas known to have been stable over the eons. If North America, Europe and Australia have received a pretty fair amount of study, the scarcity of known impact craters in South America and Africa suggests the lack of systematic inter-disciplinary studies. An algorithm based on the 'Hough transform' is also reported by the authors as very useful in the identification of impact craters from satellite imagery.

Another useful site in locating impact structures - The Earth Impact Database only lists confirmed impact structures from around the world.

After reading some articles on the subject, I'm starting to feel that buying a plane ticket for trying to find impact craters in the under explored cratons of South America or Africa is not a bad idea at all. Did you get the bug, yet?

******

(I have. I bought shares in Great Australian Resources.)

[Berosus]

This isn't the only thing that fell on the Kalahari. Remember how a coke bottle caused a case of culture shock?

[SunkenCiv]

Thanks!

[SunkenCiv]

And just to make your own fun, if that old classic is ever screened at a theater, stand up and shout, "take the Pepsi Challenge."

Uh-oh.

I wish I hadn't said that.

[Ernest_at_the_Beach]

Thanks , very interesting/

[SunkenCiv]

update:

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[SunkenCiv]

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	Gods Graves Glyphs	Morokweng crater Google Note: you posted this topic a couple of years ago. I never got the ping message posted. To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach
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