It seems that the impact, from a mountain sized object, penetrated the crust straight through. The 10km wide (approx) object vaporized on impact with such violence that the crust was inverted. The evidence is that there are no trace elements in this impact that are common at others. There are relatively high levels of iron, nickel and platinum, metals which are typically in the lower levels of our crust. Conversely there is an absence of zirconium, uranium and other elements which are common at impact sites. This suggests that the impact penetrated so deep that a plume of “superheated rock from deep down” covered the site.
More can be read at the geology science news at innovations-report.
…claimed that large ancient impacts triggered flood basalts. So much of the crust gets blasted away that even if the partially liquid aesthenosphere isn’t exposed, the drop in pressure causes the deep rocks to spontaneously melt. The crater fills up with magma and spills out. This further reduces pressure, magma keeps flowing, being replaced from below, and thus forces the formation of a hotspot. Their favorite example is the Deccan flood basalts in India. They say the impact site occurred before India and the Seychelles parted ways, and so the crater has been ripped apart by rifting. In fact, they claim that impacts actually crack the crust and start the rifting process. The idea is appealing but has its problems.
Some other people have taken the idea a bit further, suggesting that hotspots occur at the antipode of an impact.
Funnily enough, my wife and I visited Sudbury on our honeymoon :-) Well, the main part of the trip was visiting various spots of wilderness in northern Ontario, but I had an old friend in Sudbury, and had never been and wanted to visit. The lack of vegetation on most of the rocky landscape was quite noticeable.
Somehow I’d always thought the nickel in Sudbury was from the asteroid itself – it sounds like now they’re thinking it was actually Earth material dug up from below? Interesting…
The Sudbury Deep Drilling Project intends to go down and look at what is down there. Proposed are two deep wells, taking cores all the way down, and maintaining lab equipment at the bottom. Sampling of fluids is also planned, as well as examination of a “deep biosphere”. Proposed activities include placing seismic gear in hole and measuring seismic waves — an interesting comparison to existing interpretations of seismic measurements, particularly due to knowing exactly what rocks the well penetrates.
There is a pretty map of the concentric rings in the complex in the Letter of Intent.
It also is intended to be a demonstration of Canadian drilling technologies. It is claimed that Sudbury is a world leader in diamond drilling technologies and existing technologies can drill to 6,000m, although unknowns exist due to deepest Sudbury wells being 3,000m.
Bosumtwi crater in west Africa is also being examined by the International Continental Scientific Drilling Program.
The Sudbury geologic (meteoric?) formation is called the “Sudbury Igneous Complex” and web search for that phrase returns many articles. One (Evolution of the SIC: Cold in the South, Hot in the North) says that the differences between two areas are due to slightly different temperatures in two areas of the same melt body, implying a single event. A 1995 Lunar Planetary Institute paper, The Sudbury Igneous Complex – An Impact Melt Sheet? recognizes that previous work indicates it is an impact formation and there is no indication of a deep intrusion upward (as in a volcano’s pipe to the surface) but interprets the two zones as being due to two events. The new work explains there is no upward pipe because the impact exposed a large area of deep hot rock (perhaps not directly exposed it, but removed much of the pressure over it).
…very interesting. My grandmother used to tell me that the area where our farm is was turned over on itself thousands of years ago, possibly from an earthquake or volcanic activity. She said that explained why our soil was so rocky and why we have so much red clay.
All kidding aside, I’ve examined the ground and I’m not so sure its a silly theory. I live in SW Arkansas, and the region is the rolling hills south of the Ouachita mountains where the lowlands of Texas meet the hills. Lots of bottomland and sandy hills. But in the area where I live, its alot of dark red clay and rocks. And I mean rocks: gravel, conglomerates, and boulders the size of footballs. In some places there are large, volleyball-sized, spherical rocks just sitting on top of the ground.
There’s a creek that runs on one corner of our property and it has alot of sandstone and alittle shale in it. There’s white clay in the creek, different from the red clay in the ground elsewhere. And I swear I’ve found some basalt in the creek, it looks like basalt but it possibly could be black shale. But I just don’t know. I keep thinking about New Madrid, the earthquake in NW Ark hundreds of years ago and wonder if that possibly could have happened in my area further back in the past.
Hey, Drifter– I was born in Hot Springs & grew up in Little Rock. The most memorable finds in my grandparents’ farm creek (just outside Hot Springs) were not mere pebbles but Indian arrowheads. What an eerie feeling to know the presence of those who called the land theirs long before my grandfather did.
BTW, I’ve lived in Alabama for many years now– We know a thing or two about red clay, too. :-)
I was born in Little Rock and lived in Hot Springs for awhile before we moved down South. Quite the reversal realities here :D!
Yes, where we live now is rumoured to have once been an Indian spring settlement. We’ve gotten bag after bag of arrowheads here, everytime we plowed the field.